org.h2.mvstore.MVStore Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.mvstore;
import static org.h2.mvstore.MVMap.INITIAL_VERSION;
import java.lang.Thread.UncaughtExceptionHandler;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantLock;
import org.h2.compress.CompressDeflate;
import org.h2.compress.CompressLZF;
import org.h2.compress.Compressor;
import org.h2.engine.Constants;
import org.h2.mvstore.cache.CacheLongKeyLIRS;
import org.h2.util.MathUtils;
import org.h2.util.Utils;
/*
TODO:
Documentation
- rolling docs review: at "Metadata Map"
- better document that writes are in background thread
- better document how to do non-unique indexes
- document pluggable store and OffHeapStore
TransactionStore:
- ability to disable the transaction log,
if there is only one connection
MVStore:
- better and clearer memory usage accounting rules
(heap memory versus disk memory), so that even there is
never an out of memory
even for a small heap, and so that chunks
are still relatively big on average
- make sure serialization / deserialization errors don't corrupt the file
- test and possibly improve compact operation (for large dbs)
- automated 'kill process' and 'power failure' test
- defragment (re-creating maps, specially those with small pages)
- store number of write operations per page (maybe defragment
if much different than count)
- r-tree: nearest neighbor search
- use a small object value cache (StringCache), test on Android
for default serialization
- MVStoreTool.dump should dump the data if possible;
possibly using a callback for serialization
- implement a sharded map (in one store, multiple stores)
to support concurrent updates and writes, and very large maps
- to save space when persisting very small transactions,
use a transaction log where only the deltas are stored
- serialization for lists, sets, sets, sorted sets, maps, sorted maps
- maybe rename 'rollback' to 'revert' to distinguish from transactions
- support other compression algorithms (deflate, LZ4,...)
- remove features that are not really needed; simplify the code
possibly using a separate layer or tools
(retainVersion?)
- optional pluggable checksum mechanism (per page), which
requires that everything is a page (including headers)
- rename "store" to "save", as "store" is used in "storeVersion"
- rename setStoreVersion to setDataVersion, setSchemaVersion or similar
- temporary file storage
- simple rollback method (rollback to last committed version)
- MVMap to implement SortedMap, then NavigableMap
- storage that splits database into multiple files,
to speed up compact and allow using trim
(by truncating / deleting empty files)
- add new feature to the file system API to avoid copying data
(reads that returns a ByteBuffer instead of writing into one)
for memory mapped files and off-heap storage
- support log structured merge style operations (blind writes)
using one map per level plus bloom filter
- have a strict call order MVStore -> MVMap -> Page -> FileStore
- autocommit commits, stores, and compacts from time to time;
the background thread should wait at least 90% of the
configured write delay to store changes
- compact* should also store uncommitted changes (if there are any)
- write a LSM-tree (log structured merge tree) utility on top of the MVStore
with blind writes and/or a bloom filter that
internally uses regular maps and merge sort
- chunk metadata: maybe split into static and variable,
or use a small page size for metadata
- data type "string": maybe use prefix compression for keys
- test chunk id rollover
- feature to auto-compact from time to time and on close
- compact very small chunks
- Page: to save memory, combine keys & values into one array
(also children & counts). Maybe remove some other
fields (childrenCount for example)
- Support SortedMap for MVMap
- compact: copy whole pages (without having to open all maps)
- maybe change the length code to have lower gaps
- test with very low limits (such as: short chunks, small pages)
- maybe allow to read beyond the retention time:
when compacting, move live pages in old chunks
to a map (possibly the metadata map) -
this requires a change in the compaction code, plus
a map lookup when reading old data; also, this
old data map needs to be cleaned up somehow;
maybe using an additional timeout
- rollback of removeMap should restore the data -
which has big consequences, as the metadata map
would probably need references to the root nodes of all maps
*/
/**
* A persistent storage for maps.
*/
public class MVStore implements AutoCloseable {
/**
* The block size (physical sector size) of the disk. The store header is
* written twice, one copy in each block, to ensure it survives a crash.
*/
static final int BLOCK_SIZE = 4 * 1024;
private static final int FORMAT_WRITE = 1;
private static final int FORMAT_READ = 1;
/**
* Used to mark a chunk as free, when it was detected that live bookkeeping
* is incorrect.
*/
private static final int MARKED_FREE = 10_000_000;
/**
* Store is open.
*/
private static final int STATE_OPEN = 0;
/**
* Store is about to close now, but is still operational.
* Outstanding store operation by background writer or other thread may be in progress.
* New updates must not be initiated, unless they are part of a closing procedure itself.
*/
private static final int STATE_STOPPING = 1;
/**
* Store is closing now, and any operation on it may fail.
*/
private static final int STATE_CLOSING = 2;
/**
* Store is closed.
*/
private static final int STATE_CLOSED = 3;
/**
* Lock which governs access to major store operations: store(), close(), ...
* It should used in a non-reentrant fashion.
* It serves as a replacement for synchronized(this), except it allows for
* non-blocking lock attempts.
*/
private final ReentrantLock storeLock = new ReentrantLock(true);
/**
* Reference to a background thread, which is expected to be running, if any.
*/
private final AtomicReference backgroundWriterThread = new AtomicReference<>();
private volatile boolean reuseSpace = true;
private volatile int state;
private final FileStore fileStore;
private final boolean fileStoreIsProvided;
private final int pageSplitSize;
private final int keysPerPage;
/**
* The page cache. The default size is 16 MB, and the average size is 2 KB.
* It is split in 16 segments. The stack move distance is 2% of the expected
* number of entries.
*/
final CacheLongKeyLIRS cache;
/**
* The page chunk references cache. The default size is 4 MB, and the
* average size is 2 KB. It is split in 16 segments. The stack move distance
* is 2% of the expected number of entries.
*/
final CacheLongKeyLIRS cacheChunkRef;
/**
* The newest chunk. If nothing was stored yet, this field is not set.
*/
private Chunk lastChunk;
/**
* The map of chunks.
*/
private final ConcurrentHashMap chunks =
new ConcurrentHashMap<>();
private long updateCounter = 0;
private long updateAttemptCounter = 0;
/**
* The map of temporarily freed storage space caused by freed pages.
* It contains the number of freed entries per chunk.
*/
private final Map freedPageSpace = new HashMap<>();
/**
* The metadata map. Write access to this map needs to be done under storeLock.
*/
private final MVMap meta;
private final ConcurrentHashMap> maps =
new ConcurrentHashMap<>();
private final HashMap storeHeader = new HashMap<>();
private WriteBuffer writeBuffer;
private final AtomicInteger lastMapId = new AtomicInteger();
private int versionsToKeep = 5;
/**
* The compression level for new pages (0 for disabled, 1 for fast, 2 for
* high). Even if disabled, the store may contain (old) compressed pages.
*/
private final int compressionLevel;
private Compressor compressorFast;
private Compressor compressorHigh;
private final UncaughtExceptionHandler backgroundExceptionHandler;
private volatile long currentVersion;
/**
* The version of the last stored chunk, or -1 if nothing was stored so far.
*/
private long lastStoredVersion = INITIAL_VERSION;
/**
* Oldest store version in use. All version beyond this can be safely dropped
*/
private final AtomicLong oldestVersionToKeep = new AtomicLong();
/**
* Ordered collection of all version usage counters for all versions starting
* from oldestVersionToKeep and up to current.
*/
private final Deque versions = new LinkedList<>();
/**
* Counter of open transactions for the latest (current) store version
*/
private volatile TxCounter currentTxCounter = new TxCounter(currentVersion);
/**
* The estimated memory used by unsaved pages. This number is not accurate,
* also because it may be changed concurrently, and because temporary pages
* are counted.
*/
private int unsavedMemory;
private final int autoCommitMemory;
private volatile boolean saveNeeded;
/**
* The time the store was created, in milliseconds since 1970.
*/
private long creationTime;
/**
* How long to retain old, persisted chunks, in milliseconds. For larger or
* equal to zero, a chunk is never directly overwritten if unused, but
* instead, the unused field is set. If smaller zero, chunks are directly
* overwritten if unused.
*/
private int retentionTime;
private long lastCommitTime;
/**
* The version of the current store operation (if any).
*/
private volatile long currentStoreVersion = -1;
private volatile boolean metaChanged;
/**
* The delay in milliseconds to automatically commit and write changes.
*/
private int autoCommitDelay;
private final int autoCompactFillRate;
private long autoCompactLastFileOpCount;
private volatile IllegalStateException panicException;
private long lastTimeAbsolute;
private long lastFreeUnusedChunks;
/**
* Create and open the store.
*
* @param config the configuration to use
* @throws IllegalStateException if the file is corrupt, or an exception
* occurred while opening
* @throws IllegalArgumentException if the directory does not exist
*/
MVStore(Map config) {
this.compressionLevel = DataUtils.getConfigParam(config, "compress", 0);
String fileName = (String) config.get("fileName");
FileStore fileStore = (FileStore) config.get("fileStore");
fileStoreIsProvided = fileStore != null;
if(fileStore == null && fileName != null) {
fileStore = new FileStore();
}
this.fileStore = fileStore;
int pgSplitSize = 48; // for "mem:" case it is # of keys
CacheLongKeyLIRS.Config cc = null;
if (this.fileStore != null) {
int mb = DataUtils.getConfigParam(config, "cacheSize", 16);
if (mb > 0) {
cc = new CacheLongKeyLIRS.Config();
cc.maxMemory = mb * 1024L * 1024L;
Object o = config.get("cacheConcurrency");
if (o != null) {
cc.segmentCount = (Integer)o;
}
}
pgSplitSize = 16 * 1024;
}
if (cc != null) {
cache = new CacheLongKeyLIRS<>(cc);
cc.maxMemory /= 4;
cacheChunkRef = new CacheLongKeyLIRS<>(cc);
} else {
cache = null;
cacheChunkRef = null;
}
pgSplitSize = DataUtils.getConfigParam(config, "pageSplitSize", pgSplitSize);
// Make sure pages will fit into cache
if (cache != null && pgSplitSize > cache.getMaxItemSize()) {
pgSplitSize = (int)cache.getMaxItemSize();
}
pageSplitSize = pgSplitSize;
keysPerPage = DataUtils.getConfigParam(config, "keysPerPage", 48);
backgroundExceptionHandler =
(UncaughtExceptionHandler)config.get("backgroundExceptionHandler");
meta = new MVMap<>(this);
if (this.fileStore != null) {
retentionTime = this.fileStore.getDefaultRetentionTime();
// 19 KB memory is about 1 KB storage
int kb = Math.max(1, Math.min(19, Utils.scaleForAvailableMemory(64))) * 1024;
kb = DataUtils.getConfigParam(config, "autoCommitBufferSize", kb);
autoCommitMemory = kb * 1024;
autoCompactFillRate = DataUtils.getConfigParam(config, "autoCompactFillRate", 40);
char[] encryptionKey = (char[]) config.get("encryptionKey");
try {
if (!fileStoreIsProvided) {
boolean readOnly = config.containsKey("readOnly");
this.fileStore.open(fileName, readOnly, encryptionKey);
}
if (this.fileStore.size() == 0) {
creationTime = getTimeAbsolute();
lastCommitTime = creationTime;
storeHeader.put("H", 2);
storeHeader.put("blockSize", BLOCK_SIZE);
storeHeader.put("format", FORMAT_WRITE);
storeHeader.put("created", creationTime);
writeStoreHeader();
} else {
readStoreHeader();
}
} catch (IllegalStateException e) {
panic(e);
} finally {
if (encryptionKey != null) {
Arrays.fill(encryptionKey, (char) 0);
}
}
lastCommitTime = getTimeSinceCreation();
Set rootsToRemove = new HashSet<>();
for (Iterator it = meta.keyIterator("root."); it.hasNext();) {
String key = it.next();
if (!key.startsWith("root.")) {
break;
}
String mapId = key.substring(key.lastIndexOf('.') + 1);
if(!meta.containsKey("map."+mapId)) {
rootsToRemove.add(key);
}
}
for (String key : rootsToRemove) {
meta.remove(key);
markMetaChanged();
}
// setAutoCommitDelay starts the thread, but only if
// the parameter is different from the old value
int delay = DataUtils.getConfigParam(config, "autoCommitDelay", 1000);
setAutoCommitDelay(delay);
} else {
autoCommitMemory = 0;
autoCompactFillRate = 0;
}
}
private void panic(IllegalStateException e) {
if (isOpen()) {
handleException(e);
panicException = e;
closeImmediately();
}
throw e;
}
public IllegalStateException getPanicException() {
return panicException;
}
/**
* Open a store in exclusive mode. For a file-based store, the parent
* directory must already exist.
*
* @param fileName the file name (null for in-memory)
* @return the store
*/
public static MVStore open(String fileName) {
HashMap config = new HashMap<>();
config.put("fileName", fileName);
return new MVStore(config);
}
/**
* Find position of the root page for historical version of the map.
*
* @param mapId to find the old version for
* @param version the version
* @return position of the root Page
*/
long getRootPos(int mapId, long version) {
MVMap oldMeta = getMetaMap(version);
return getRootPos(oldMeta, mapId);
}
/**
* Open a map with the default settings. The map is automatically create if
* it does not yet exist. If a map with this name is already open, this map
* is returned.
*
* @param the key type
* @param the value type
* @param name the name of the map
* @return the map
*/
public MVMap openMap(String name) {
return openMap(name, new MVMap.Builder());
}
/**
* Open a map with the given builder. The map is automatically create if it
* does not yet exist. If a map with this name is already open, this map is
* returned.
*
* @param the map type
* @param the key type
* @param the value type
* @param name the name of the map
* @param builder the map builder
* @return the map
*/
public , K, V> M openMap(String name, MVMap.MapBuilder builder) {
int id = getMapId(name);
M map;
if (id >= 0) {
map = openMap(id, builder);
assert builder.getKeyType() == null || map.getKeyType().getClass().equals(builder.getKeyType().getClass());
assert builder.getValueType() == null || map.getValueType().getClass().equals(builder.getValueType()
.getClass());
} else {
HashMap c = new HashMap<>();
id = lastMapId.incrementAndGet();
assert getMap(id) == null;
c.put("id", id);
c.put("createVersion", currentVersion);
map = builder.create(this, c);
String x = Integer.toHexString(id);
meta.put(MVMap.getMapKey(id), map.asString(name));
meta.put("name." + name, x);
map.setRootPos(0, lastStoredVersion);
markMetaChanged();
@SuppressWarnings("unchecked")
M existingMap = (M) maps.putIfAbsent(id, map);
if (existingMap != null) {
map = existingMap;
}
}
return map;
}
private , K, V> M openMap(int id, MVMap.MapBuilder builder) {
storeLock.lock();
try {
@SuppressWarnings("unchecked")
M map = (M) getMap(id);
if (map == null) {
String configAsString = meta.get(MVMap.getMapKey(id));
HashMap config;
if (configAsString != null) {
config = new HashMap(DataUtils.parseMap(configAsString));
} else {
config = new HashMap<>();
}
config.put("id", id);
map = builder.create(this, config);
long root = getRootPos(meta, id);
map.setRootPos(root, lastStoredVersion);
maps.put(id, map);
}
return map;
} finally {
storeLock.unlock();
}
}
/**
* Get map by id.
*
* @param the key type
* @param the value type
* @param id map id
* @return Map
*/
public MVMap getMap(int id) {
checkOpen();
@SuppressWarnings("unchecked")
MVMap map = (MVMap) maps.get(id);
return map;
}
/**
* Get the set of all map names.
*
* @return the set of names
*/
public Set getMapNames() {
HashSet set = new HashSet<>();
checkOpen();
for (Iterator it = meta.keyIterator("name."); it.hasNext();) {
String x = it.next();
if (!x.startsWith("name.")) {
break;
}
String mapName = x.substring("name.".length());
set.add(mapName);
}
return set;
}
/**
* Get the metadata map. This data is for informational purposes only. The
* data is subject to change in future versions.
*
* The data in this map should not be modified (changing system data may
* corrupt the store). If modifications are needed, they need be
* synchronized on the store.
*
* The metadata map contains the following entries:
*
* chunk.{chunkId} = {chunk metadata}
* name.{name} = {mapId}
* map.{mapId} = {map metadata}
* root.{mapId} = {root position}
* setting.storeVersion = {version}
*
*
* @return the metadata map
*/
public MVMap getMetaMap() {
checkOpen();
return meta;
}
private MVMap getMetaMap(long version) {
Chunk c = getChunkForVersion(version);
DataUtils.checkArgument(c != null, "Unknown version {0}", version);
c = readChunkHeader(c.block);
MVMap oldMeta = meta.openReadOnly(c.metaRootPos, version);
return oldMeta;
}
private Chunk getChunkForVersion(long version) {
Chunk newest = null;
for (Chunk c : chunks.values()) {
if (c.version <= version) {
if (newest == null || c.id > newest.id) {
newest = c;
}
}
}
return newest;
}
/**
* Check whether a given map exists.
*
* @param name the map name
* @return true if it exists
*/
public boolean hasMap(String name) {
return meta.containsKey("name." + name);
}
/**
* Check whether a given map exists and has data.
*
* @param name the map name
* @return true if it exists and has data.
*/
public boolean hasData(String name) {
return hasMap(name) && getRootPos(meta, getMapId(name)) != 0;
}
private void markMetaChanged() {
// changes in the metadata alone are usually not detected, as the meta
// map is changed after storing
metaChanged = true;
}
private void readStoreHeader() {
Chunk newest = null;
boolean validStoreHeader = false;
// find out which chunk and version are the newest
// read the first two blocks
ByteBuffer fileHeaderBlocks = fileStore.readFully(0, 2 * BLOCK_SIZE);
byte[] buff = new byte[BLOCK_SIZE];
for (int i = 0; i <= BLOCK_SIZE; i += BLOCK_SIZE) {
fileHeaderBlocks.get(buff);
// the following can fail for various reasons
try {
HashMap m = DataUtils.parseChecksummedMap(buff);
if (m == null) {
continue;
}
int blockSize = DataUtils.readHexInt(
m, "blockSize", BLOCK_SIZE);
if (blockSize != BLOCK_SIZE) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_UNSUPPORTED_FORMAT,
"Block size {0} is currently not supported",
blockSize);
}
long version = DataUtils.readHexLong(m, "version", 0);
if (newest == null || version > newest.version) {
validStoreHeader = true;
storeHeader.putAll(m);
creationTime = DataUtils.readHexLong(m, "created", 0);
int chunkId = DataUtils.readHexInt(m, "chunk", 0);
long block = DataUtils.readHexLong(m, "block", 0);
Chunk test = readChunkHeaderAndFooter(block);
if (test != null && test.id == chunkId) {
newest = test;
}
}
} catch (Exception ignore) {/**/}
}
if (!validStoreHeader) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_FILE_CORRUPT,
"Store header is corrupt: {0}", fileStore);
}
long format = DataUtils.readHexLong(storeHeader, "format", 1);
if (format > FORMAT_WRITE && !fileStore.isReadOnly()) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_UNSUPPORTED_FORMAT,
"The write format {0} is larger " +
"than the supported format {1}, " +
"and the file was not opened in read-only mode",
format, FORMAT_WRITE);
}
format = DataUtils.readHexLong(storeHeader, "formatRead", format);
if (format > FORMAT_READ) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_UNSUPPORTED_FORMAT,
"The read format {0} is larger " +
"than the supported format {1}",
format, FORMAT_READ);
}
lastStoredVersion = INITIAL_VERSION;
chunks.clear();
long now = System.currentTimeMillis();
// calculate the year (doesn't have to be exact;
// we assume 365.25 days per year, * 4 = 1461)
int year = 1970 + (int) (now / (1000L * 60 * 60 * 6 * 1461));
if (year < 2014) {
// if the year is before 2014,
// we assume the system doesn't have a real-time clock,
// and we set the creationTime to the past, so that
// existing chunks are overwritten
creationTime = now - fileStore.getDefaultRetentionTime();
} else if (now < creationTime) {
// the system time was set to the past:
// we change the creation time
creationTime = now;
storeHeader.put("created", creationTime);
}
Chunk test = readChunkFooter(fileStore.size());
if (test != null) {
test = readChunkHeaderAndFooter(test.block);
if (test != null) {
if (newest == null || test.version > newest.version) {
newest = test;
}
}
}
long blocksInStore = fileStore.size() / BLOCK_SIZE;
// this queue will hold potential candidates for lastChunk to fall back to
Queue lastChunkCandidates = new PriorityQueue<>(Math.max(32, (int)(blocksInStore / 4)),
new Comparator() {
@Override
public int compare(Chunk one, Chunk two) {
int result = Long.compare(two.version, one.version);
if (result == 0) {
// out of two versions of the same chunk we prefer the one
// close to the beginning of file (presumably later version)
result = Long.compare(one.block, two.block);
}
return result;
}
});
Map validChunkCacheByLocation = new HashMap<>();
if (newest != null) {
// read the chunk header and footer,
// and follow the chain of next chunks
while (true) {
validChunkCacheByLocation.put(newest.block, newest);
lastChunkCandidates.add(newest);
if (newest.next == 0 ||
newest.next >= blocksInStore) {
// no (valid) next
break;
}
test = readChunkHeaderAndFooter(newest.next);
if (test == null || test.id <= newest.id) {
break;
}
newest = test;
}
}
// Try candidates for "last chunk" in order from newest to oldest
// until suitable is found. Suitable one should have meta map
// where all chunk references point to valid locations.
boolean verified = false;
while(!verified && setLastChunk(lastChunkCandidates.poll()) != null) {
verified = true;
// load the chunk metadata: although meta's root page resides in the lastChunk,
// traversing meta map might recursively load another chunk(s)
Cursor cursor = meta.cursor("chunk.");
while (cursor.hasNext() && cursor.next().startsWith("chunk.")) {
Chunk c = Chunk.fromString(cursor.getValue());
assert c.version <= currentVersion;
// might be there already, due to meta traversal
// see readPage() ... getChunkIfFound()
chunks.putIfAbsent(c.id, c);
long block = c.block;
test = validChunkCacheByLocation.get(block);
if (test == null) {
test = readChunkHeaderAndFooter(block);
if (test != null && test.id == c.id) { // chunk is valid
validChunkCacheByLocation.put(block, test);
lastChunkCandidates.offer(test);
continue;
}
} else if (test.id == c.id) { // chunk is valid
// nothing to do, since chunk was already verified
// and registered as potential "last chunk" candidate
continue;
}
// chunk reference is invalid
// this "last chunk" candidate is not suitable
// but we continue to process all references
// to find other potential candidates
verified = false;
}
}
fileStore.clear();
// build the free space list
for (Chunk c : chunks.values()) {
long start = c.block * BLOCK_SIZE;
int length = c.len * BLOCK_SIZE;
fileStore.markUsed(start, length);
}
assert fileStore.getFileLengthInUse() == measureFileLengthInUse() :
fileStore.getFileLengthInUse() + " != " + measureFileLengthInUse();
setWriteVersion(currentVersion);
if (lastStoredVersion == INITIAL_VERSION) {
lastStoredVersion = currentVersion - 1;
}
}
private Chunk setLastChunk(Chunk last) {
chunks.clear();
lastChunk = last;
if (last == null) {
// no valid chunk
lastMapId.set(0);
currentVersion = 0;
lastStoredVersion = INITIAL_VERSION;
meta.setRootPos(0, INITIAL_VERSION);
} else {
lastMapId.set(last.mapId);
currentVersion = last.version;
chunks.put(last.id, last);
lastStoredVersion = currentVersion - 1;
meta.setRootPos(last.metaRootPos, lastStoredVersion);
}
return last;
}
/**
* Read a chunk header and footer, and verify the stored data is consistent.
*
* @param block the block
* @return the chunk, or null if the header or footer don't match or are not
* consistent
*/
private Chunk readChunkHeaderAndFooter(long block) {
Chunk header;
try {
header = readChunkHeader(block);
} catch (Exception e) {
// invalid chunk header: ignore, but stop
return null;
}
if (header == null) {
return null;
}
Chunk footer = readChunkFooter((block + header.len) * BLOCK_SIZE);
if (footer == null || footer.id != header.id) {
return null;
}
return header;
}
/**
* Try to read a chunk footer.
*
* @param end the end of the chunk
* @return the chunk, or null if not successful
*/
private Chunk readChunkFooter(long end) {
// the following can fail for various reasons
try {
// read the chunk footer of the last block of the file
long pos = end - Chunk.FOOTER_LENGTH;
if(pos < 0) {
return null;
}
ByteBuffer lastBlock = fileStore.readFully(pos, Chunk.FOOTER_LENGTH);
byte[] buff = new byte[Chunk.FOOTER_LENGTH];
lastBlock.get(buff);
HashMap m = DataUtils.parseChecksummedMap(buff);
if (m != null) {
int chunk = DataUtils.readHexInt(m, "chunk", 0);
Chunk c = new Chunk(chunk);
c.version = DataUtils.readHexLong(m, "version", 0);
c.block = DataUtils.readHexLong(m, "block", 0);
return c;
}
} catch (Exception e) {
// ignore
}
return null;
}
private void writeStoreHeader() {
StringBuilder buff = new StringBuilder(112);
if (lastChunk != null) {
storeHeader.put("block", lastChunk.block);
storeHeader.put("chunk", lastChunk.id);
storeHeader.put("version", lastChunk.version);
}
DataUtils.appendMap(buff, storeHeader);
byte[] bytes = buff.toString().getBytes(StandardCharsets.ISO_8859_1);
int checksum = DataUtils.getFletcher32(bytes, 0, bytes.length);
DataUtils.appendMap(buff, "fletcher", checksum);
buff.append('\n');
bytes = buff.toString().getBytes(StandardCharsets.ISO_8859_1);
ByteBuffer header = ByteBuffer.allocate(2 * BLOCK_SIZE);
header.put(bytes);
header.position(BLOCK_SIZE);
header.put(bytes);
header.rewind();
write(0, header);
}
private void write(long pos, ByteBuffer buffer) {
try {
fileStore.writeFully(pos, buffer);
} catch (IllegalStateException e) {
panic(e);
}
}
/**
* Close the file and the store. Unsaved changes are written to disk first.
*/
@Override
public void close() {
closeStore(true);
}
/**
* Close the file and the store, without writing anything.
* This will try to stop the background thread (without waiting for it).
* This method ignores all errors.
*/
public void closeImmediately() {
try {
closeStore(false);
} catch (Throwable e) {
handleException(e);
}
}
private void closeStore(boolean normalShutdown) {
// If any other thead have already initiated closure procedure,
// isClosed() would wait until closure is done and then we jump out of the loop.
// This is a subtle difference between !isClosed() and isOpen().
while (!isClosed()) {
stopBackgroundThread(normalShutdown);
storeLock.lock();
try {
if (state == STATE_OPEN) {
state = STATE_STOPPING;
try {
try {
if (normalShutdown && fileStore != null && !fileStore.isReadOnly()) {
for (MVMap map : maps.values()) {
if (map.isClosed()) {
if (meta.remove(MVMap.getMapRootKey(map.getId())) != null) {
markMetaChanged();
}
}
}
commit();
shrinkFileIfPossible(0);
}
state = STATE_CLOSING;
// release memory early - this is important when called
// because of out of memory
if (cache != null) {
cache.clear();
}
if (cacheChunkRef != null) {
cacheChunkRef.clear();
}
for (MVMap m : new ArrayList<>(maps.values())) {
m.close();
}
chunks.clear();
maps.clear();
} finally {
if (fileStore != null && !fileStoreIsProvided) {
fileStore.close();
}
}
} finally {
state = STATE_CLOSED;
}
}
} finally {
storeLock.unlock();
}
}
}
/**
* Read a page of data into a ByteBuffer.
*
* @param pos page pos
* @param expectedMapId expected map id for the page
* @return ByteBuffer containing page data.
*/
ByteBuffer readBufferForPage(long pos, int expectedMapId) {
Chunk c = getChunk(pos);
long filePos = c.block * BLOCK_SIZE;
filePos += DataUtils.getPageOffset(pos);
if (filePos < 0) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_FILE_CORRUPT,
"Negative position {0}; p={1}, c={2}", filePos, pos, c.toString());
}
long maxPos = (c.block + c.len) * BLOCK_SIZE;
ByteBuffer buff;
int maxLength = DataUtils.getPageMaxLength(pos);
if (maxLength == DataUtils.PAGE_LARGE) {
buff = fileStore.readFully(filePos, 128);
maxLength = buff.getInt();
// read the first bytes again
}
maxLength = (int) Math.min(maxPos - filePos, maxLength);
int length = maxLength;
if (length < 0) {
throw DataUtils.newIllegalStateException(DataUtils.ERROR_FILE_CORRUPT,
"Illegal page length {0} reading at {1}; max pos {2} ", length, filePos, maxPos);
}
buff = fileStore.readFully(filePos, length);
int chunkId = DataUtils.getPageChunkId(pos);
int offset = DataUtils.getPageOffset(pos);
int start = buff.position();
int remaining = buff.remaining();
int pageLength = buff.getInt();
if (pageLength > remaining || pageLength < 4) {
throw DataUtils.newIllegalStateException(DataUtils.ERROR_FILE_CORRUPT,
"File corrupted in chunk {0}, expected page length 4..{1}, got {2}", chunkId, remaining,
pageLength);
}
buff.limit(start + pageLength);
short check = buff.getShort();
int mapId = DataUtils.readVarInt(buff);
if (mapId != expectedMapId) {
throw DataUtils.newIllegalStateException(DataUtils.ERROR_FILE_CORRUPT,
"File corrupted in chunk {0}, expected map id {1}, got {2}", chunkId, expectedMapId, mapId);
}
int checkTest = DataUtils.getCheckValue(chunkId)
^ DataUtils.getCheckValue(offset)
^ DataUtils.getCheckValue(pageLength);
if (check != (short) checkTest) {
throw DataUtils.newIllegalStateException(DataUtils.ERROR_FILE_CORRUPT,
"File corrupted in chunk {0}, expected check value {1}, got {2}", chunkId, checkTest, check);
}
return buff;
}
/**
* Get the chunk for the given position.
*
* @param pos the position
* @return the chunk
*/
private Chunk getChunk(long pos) {
int chunkId = DataUtils.getPageChunkId(pos);
Chunk c = chunks.get(chunkId);
if (c == null) {
checkOpen();
String s = meta.get(Chunk.getMetaKey(chunkId));
if (s == null) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_CHUNK_NOT_FOUND,
"Chunk {0} not found", chunkId);
}
c = Chunk.fromString(s);
if (c.block == Long.MAX_VALUE) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_FILE_CORRUPT,
"Chunk {0} is invalid", chunkId);
}
chunks.put(c.id, c);
}
return c;
}
private void setWriteVersion(long version) {
for (Iterator> iter = maps.values().iterator(); iter.hasNext(); ) {
MVMap map = iter.next();
if (map.setWriteVersion(version) == null) {
assert map.isClosed();
assert map.getVersion() < getOldestVersionToKeep();
meta.remove(MVMap.getMapRootKey(map.getId()));
markMetaChanged();
iter.remove();
}
}
meta.setWriteVersion(version);
onVersionChange(version);
}
/**
* Unlike regular commit this method returns immediately if there is commit
* in progress on another thread, otherwise it acts as regular commit.
*
* This method may return BEFORE this thread changes are actually persisted!
*
* @return the new version (incremented if there were changes)
*/
public long tryCommit() {
// we need to prevent re-entrance, which may be possible,
// because meta map is modified within storeNow() and that
// causes beforeWrite() call with possibility of going back here
if ((!storeLock.isHeldByCurrentThread() || currentStoreVersion < 0) &&
storeLock.tryLock()) {
try {
store();
} finally {
storeLock.unlock();
}
}
return currentVersion;
}
/**
* Commit the changes.
*
* This method does nothing if there are no unsaved changes,
* otherwise it increments the current version
* and stores the data (for file based stores).
*
* It is not necessary to call this method when auto-commit is enabled (the default
* setting), as in this case it is automatically called from time to time or
* when enough changes have accumulated. However, it may still be called to
* flush all changes to disk.
*
* At most one store operation may run at any time.
*
* @return the new version (incremented if there were changes)
*/
public long commit() {
// we need to prevent re-entrance, which may be possible,
// because meta map is modified within storeNow() and that
// causes beforeWrite() call with possibility of going back here
if(!storeLock.isHeldByCurrentThread() || currentStoreVersion < 0) {
storeLock.lock();
try {
store();
} finally {
storeLock.unlock();
}
}
return currentVersion;
}
private void store() {
try {
if (isOpenOrStopping() && hasUnsavedChangesInternal()) {
currentStoreVersion = currentVersion;
if (fileStore == null) {
lastStoredVersion = currentVersion;
//noinspection NonAtomicOperationOnVolatileField
++currentVersion;
setWriteVersion(currentVersion);
metaChanged = false;
} else {
if (fileStore.isReadOnly()) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_WRITING_FAILED, "This store is read-only");
}
try {
storeNow();
} catch (IllegalStateException e) {
panic(e);
} catch (Throwable e) {
panic(DataUtils.newIllegalStateException(DataUtils.ERROR_INTERNAL, e.toString(), e));
}
}
}
} finally {
// in any case reset the current store version,
// to allow closing the store
currentStoreVersion = -1;
}
}
private void storeNow() {
assert storeLock.isHeldByCurrentThread();
long time = getTimeSinceCreation();
freeUnusedIfNeeded(time);
int currentUnsavedPageCount = unsavedMemory;
long storeVersion = currentStoreVersion;
long version = ++currentVersion;
lastCommitTime = time;
// the metadata of the last chunk was not stored so far, and needs to be
// set now (it's better not to update right after storing, because that
// would modify the meta map again)
int lastChunkId;
if (lastChunk == null) {
lastChunkId = 0;
} else {
lastChunkId = lastChunk.id;
meta.put(Chunk.getMetaKey(lastChunkId), lastChunk.asString());
markMetaChanged();
// never go backward in time
time = Math.max(lastChunk.time, time);
}
int newChunkId = lastChunkId;
while (true) {
newChunkId = (newChunkId + 1) & Chunk.MAX_ID;
Chunk old = chunks.get(newChunkId);
if (old == null) {
break;
}
if (old.block == Long.MAX_VALUE) {
IllegalStateException e = DataUtils.newIllegalStateException(
DataUtils.ERROR_INTERNAL,
"Last block {0} not stored, possibly due to out-of-memory", old);
panic(e);
}
}
Chunk c = new Chunk(newChunkId);
c.pageCount = Integer.MAX_VALUE;
c.pageCountLive = Integer.MAX_VALUE;
c.maxLen = Long.MAX_VALUE;
c.maxLenLive = Long.MAX_VALUE;
c.metaRootPos = Long.MAX_VALUE;
c.block = Long.MAX_VALUE;
c.len = Integer.MAX_VALUE;
c.time = time;
c.version = version;
c.mapId = lastMapId.get();
c.next = Long.MAX_VALUE;
chunks.put(c.id, c);
ArrayList changed = new ArrayList<>();
for (Iterator> iter = maps.values().iterator(); iter.hasNext(); ) {
MVMap map = iter.next();
RootReference rootReference = map.setWriteVersion(version);
if (rootReference == null) {
assert map.isClosed();
assert map.getVersion() < getOldestVersionToKeep();
meta.remove(MVMap.getMapRootKey(map.getId()));
iter.remove();
} else if (map.getCreateVersion() <= storeVersion && // if map was created after storing started, skip it
!map.isVolatile() &&
map.hasChangesSince(lastStoredVersion)) {
assert rootReference.version <= version : rootReference.version + " > " + version;
Page rootPage = rootReference.root;
if (!rootPage.isSaved() ||
// after deletion previously saved leaf
// may pop up as a root, but we still need
// to save new root pos in meta
rootPage.isLeaf()) {
changed.add(rootPage);
}
}
}
WriteBuffer buff = getWriteBuffer();
// need to patch the header later
c.writeChunkHeader(buff, 0);
int headerLength = buff.position();
c.pageCount = 0;
c.pageCountLive = 0;
c.maxLen = 0;
c.maxLenLive = 0;
for (Page p : changed) {
String key = MVMap.getMapRootKey(p.getMapId());
if (p.getTotalCount() == 0) {
meta.remove(key);
} else {
p.writeUnsavedRecursive(c, buff);
long root = p.getPos();
meta.put(key, Long.toHexString(root));
}
}
applyFreedSpace();
RootReference metaRootReference = meta.setWriteVersion(version);
assert metaRootReference != null;
assert metaRootReference.version == version : metaRootReference.version + " != " + version;
metaChanged = false;
onVersionChange(version);
Page metaRoot = metaRootReference.root;
metaRoot.writeUnsavedRecursive(c, buff);
int chunkLength = buff.position();
// add the store header and round to the next block
int length = MathUtils.roundUpInt(chunkLength +
Chunk.FOOTER_LENGTH, BLOCK_SIZE);
buff.limit(length);
long filePos = allocateFileSpace(length, !reuseSpace);
c.block = filePos / BLOCK_SIZE;
c.len = length / BLOCK_SIZE;
assert fileStore.getFileLengthInUse() == measureFileLengthInUse() :
fileStore.getFileLengthInUse() + " != " + measureFileLengthInUse() + " " + c;
c.metaRootPos = metaRoot.getPos();
// calculate and set the likely next position
if (reuseSpace) {
c.next = fileStore.predictAllocation(c.len * BLOCK_SIZE) / BLOCK_SIZE;
} else {
// just after this chunk
c.next = 0;
}
buff.position(0);
c.writeChunkHeader(buff, headerLength);
buff.position(buff.limit() - Chunk.FOOTER_LENGTH);
buff.put(c.getFooterBytes());
buff.position(0);
write(filePos, buff.getBuffer());
releaseWriteBuffer(buff);
// whether we need to write the store header
boolean writeStoreHeader = false;
// end of the used space is not necessarily the end of the file
boolean storeAtEndOfFile = filePos + length >= fileStore.size();
if (!storeAtEndOfFile) {
if (lastChunk == null) {
writeStoreHeader = true;
} else if (lastChunk.next != c.block) {
// the last prediction did not matched
writeStoreHeader = true;
} else {
long headerVersion = DataUtils.readHexLong(
storeHeader, "version", 0);
if (lastChunk.version - headerVersion > 20) {
// we write after at least every 20 versions
writeStoreHeader = true;
} else {
int chunkId = DataUtils.readHexInt(storeHeader, "chunk", 0);
while (true) {
Chunk old = chunks.get(chunkId);
if (old == null) {
// one of the chunks in between
// was removed
writeStoreHeader = true;
break;
}
if (chunkId == lastChunk.id) {
break;
}
chunkId++;
}
}
}
}
lastChunk = c;
if (writeStoreHeader) {
writeStoreHeader();
}
if (!storeAtEndOfFile) {
// may only shrink after the store header was written
shrinkFileIfPossible(1);
}
for (Page p : changed) {
p.writeEnd();
}
metaRoot.writeEnd();
// some pages might have been changed in the meantime (in the newest
// version)
unsavedMemory = Math.max(0, unsavedMemory
- currentUnsavedPageCount);
lastStoredVersion = storeVersion;
}
/**
* Try to free unused chunks. This method doesn't directly write, but can
* change the metadata, and therefore cause a background write.
*/
private void freeUnusedIfNeeded(long time) {
int freeDelay = retentionTime / 5;
if (time - lastFreeUnusedChunks >= freeDelay) {
// set early in case it fails (out of memory or so)
lastFreeUnusedChunks = time;
freeUnusedChunks(true);
}
}
private void freeUnusedChunks(boolean fast) {
assert storeLock.isHeldByCurrentThread();
if (lastChunk != null && reuseSpace) {
Set referenced = collectReferencedChunks(fast);
long time = getTimeSinceCreation();
for (Iterator iterator = chunks.values().iterator(); iterator.hasNext(); ) {
Chunk c = iterator.next();
if (c.block != Long.MAX_VALUE && !referenced.contains(c.id)) {
if (canOverwriteChunk(c, time)) {
iterator.remove();
if (meta.remove(Chunk.getMetaKey(c.id)) != null) {
markMetaChanged();
}
long start = c.block * BLOCK_SIZE;
int length = c.len * BLOCK_SIZE;
fileStore.free(start, length);
assert fileStore.getFileLengthInUse() == measureFileLengthInUse() :
fileStore.getFileLengthInUse() + " != " + measureFileLengthInUse();
} else {
if (c.unused == 0) {
c.unused = time;
meta.put(Chunk.getMetaKey(c.id), c.asString());
markMetaChanged();
}
}
}
}
// set it here, to avoid calling it often if it was slow
lastFreeUnusedChunks = getTimeSinceCreation();
}
}
/**
* Collect ids for chunks that are in use.
* @param fast if true, simplified version is used, which assumes that recent chunks
* are still in-use and do not scan recent versions of the store.
* Also is this case only oldest available version of the store is scanned.
* @return set of chunk ids in-use, or null if all chunks should be considered in-use
*/
private Set collectReferencedChunks(boolean fast) {
assert lastChunk != null;
final ThreadPoolExecutor executorService = new ThreadPoolExecutor(10, 10, 10L, TimeUnit.SECONDS,
new ArrayBlockingQueue(keysPerPage + 1));
final AtomicInteger executingThreadCounter = new AtomicInteger();
try {
ChunkIdsCollector collector = new ChunkIdsCollector(meta.getId());
long oldestVersionToKeep = getOldestVersionToKeep();
RootReference rootReference = meta.flushAndGetRoot();
if (fast) {
RootReference previous;
while (rootReference.version >= oldestVersionToKeep && (previous = rootReference.previous) != null) {
rootReference = previous;
}
inspectVersion(rootReference, collector, executorService, executingThreadCounter, null);
Page rootPage = rootReference.root;
long pos = rootPage.getPos();
assert rootPage.isSaved();
int chunkId = DataUtils.getPageChunkId(pos);
while (++chunkId <= lastChunk.id) {
collector.registerChunk(chunkId);
}
} else {
Set inspectedRoots = new HashSet<>();
do {
inspectVersion(rootReference, collector, executorService, executingThreadCounter, inspectedRoots);
} while (rootReference.version >= oldestVersionToKeep
&& (rootReference = rootReference.previous) != null);
}
return collector.getReferenced();
} finally {
executorService.shutdownNow();
}
}
/**
* Scans all map of a particular store version and marks visited chunks as in-use.
* @param rootReference of the meta map of the version
* @param collector to report visited chunks to
* @param executorService to use for parallel processing
* @param executingThreadCounter counter for threads already in use
* @param inspectedRoots set of page positions for map's roots already inspected
* or null if not to be used
*/
private void inspectVersion(RootReference rootReference, ChunkIdsCollector collector,
ThreadPoolExecutor executorService,
AtomicInteger executingThreadCounter,
Set inspectedRoots) {
Page rootPage = rootReference.root;
long pos = rootPage.getPos();
if (rootPage.isSaved()) {
if (inspectedRoots != null && !inspectedRoots.add(pos)) {
return;
}
collector.setMapId(meta.getId());
collector.visit(pos, executorService, executingThreadCounter);
}
for (Cursor c = new Cursor<>(rootPage, "root."); c.hasNext(); ) {
String key = c.next();
if (!key.startsWith("root.")) {
break;
}
pos = DataUtils.parseHexLong(c.getValue());
if (DataUtils.isPageSaved(pos)) {
if (inspectedRoots == null || inspectedRoots.add(pos)) {
// to allow for something like "root.tmp.123" to be processed
int mapId = DataUtils.parseHexInt(key.substring(key.lastIndexOf('.') + 1));
collector.setMapId(mapId);
collector.visit(pos, executorService, executingThreadCounter);
}
}
}
}
final class ChunkIdsCollector {
/** really a set */
private final ConcurrentHashMap referencedChunks = new ConcurrentHashMap<>();
private final ChunkIdsCollector parent;
private int mapId;
ChunkIdsCollector(int mapId) {
this.parent = null;
this.mapId = mapId;
}
private ChunkIdsCollector(ChunkIdsCollector parent) {
this.parent = parent;
this.mapId = parent.mapId;
}
public int getMapId() {
return mapId;
}
public void setMapId(int mapId) {
this.mapId = mapId;
}
public Set getReferenced() {
return new HashSet<>(referencedChunks.keySet());
}
/**
* Visit a page on a chunk and collect ids for it and its children.
*
* @param page the page to visit
* @param executorService the service to use when doing visit in parallel
* @param executingThreadCounter number of threads currently active
*/
public void visit(Page page, ThreadPoolExecutor executorService, AtomicInteger executingThreadCounter) {
long pos = page.getPos();
if (DataUtils.isPageSaved(pos)) {
registerChunk(DataUtils.getPageChunkId(pos));
}
int count = page.map.getChildPageCount(page);
if (count == 0) {
return;
}
ChunkIdsCollector childCollector = DataUtils.isPageSaved(pos) && cacheChunkRef != null ?
new ChunkIdsCollector(this) : this;
for (int i = 0; i < count; i++) {
Page childPage = page.getChildPageIfLoaded(i);
if (childPage != null) {
childCollector.visit(childPage, executorService, executingThreadCounter);
} else {
childCollector.visit(page.getChildPagePos(i), executorService, executingThreadCounter);
}
}
cacheCollectedChunkIds(pos, childCollector);
}
/**
* Visit a page on a chunk and collect ids for it and its children.
*
* @param pos position of the page to visit
* @param executorService the service to use when doing visit in parallel
* @param executingThreadCounter number of threads currently active
*/
public void visit(long pos, ThreadPoolExecutor executorService, AtomicInteger executingThreadCounter) {
if (!DataUtils.isPageSaved(pos)) {
return;
}
registerChunk(DataUtils.getPageChunkId(pos));
if (DataUtils.getPageType(pos) == DataUtils.PAGE_TYPE_LEAF) {
return;
}
int[] chunkIds;
if (cacheChunkRef != null && (chunkIds = cacheChunkRef.get(pos)) != null) {
// there is a cached set of chunk ids for this position
for (int chunkId : chunkIds) {
registerChunk(chunkId);
}
} else {
ChunkIdsCollector childCollector = cacheChunkRef != null ? new ChunkIdsCollector(this) : this;
Page page;
if (cache != null && (page = cache.get(pos)) != null) {
// there is a full page in cache, use it
childCollector.visit(page, executorService, executingThreadCounter);
} else {
// page was not cached: read the data
ByteBuffer buff = readBufferForPage(pos, getMapId());
Page.readChildrenPositions(buff, pos, childCollector, executorService, executingThreadCounter);
}
cacheCollectedChunkIds(pos, childCollector);
}
}
/**
* Add chunk to list of referenced chunks.
*
* @param chunkId chunk id
*/
void registerChunk(int chunkId) {
if (referencedChunks.put(chunkId, 1) == null && parent != null) {
parent.registerChunk(chunkId);
}
}
private void cacheCollectedChunkIds(long pos, ChunkIdsCollector childCollector) {
if (childCollector != this) {
int[] chunkIds = new int[childCollector.referencedChunks.size()];
int index = 0;
for (Integer chunkId : childCollector.referencedChunks.keySet()) {
chunkIds[index++] = chunkId;
}
cacheChunkRef.put(pos, chunkIds, Constants.MEMORY_ARRAY + 4 * chunkIds.length);
}
}
}
/**
* Get a buffer for writing. This caller must synchronize on the store
* before calling the method and until after using the buffer.
*
* @return the buffer
*/
private WriteBuffer getWriteBuffer() {
WriteBuffer buff;
if (writeBuffer != null) {
buff = writeBuffer;
buff.clear();
} else {
buff = new WriteBuffer();
}
return buff;
}
/**
* Release a buffer for writing. This caller must synchronize on the store
* before calling the method and until after using the buffer.
*
* @param buff the buffer than can be re-used
*/
private void releaseWriteBuffer(WriteBuffer buff) {
if (buff.capacity() <= 4 * 1024 * 1024) {
writeBuffer = buff;
}
}
private boolean canOverwriteChunk(Chunk c, long time) {
if (retentionTime >= 0) {
if (c.time + retentionTime > time) {
return false;
}
if (c.unused == 0 || c.unused + retentionTime / 2 > time) {
return false;
}
}
return true;
}
private long getTimeSinceCreation() {
return Math.max(0, getTimeAbsolute() - creationTime);
}
private long getTimeAbsolute() {
long now = System.currentTimeMillis();
if (lastTimeAbsolute != 0 && now < lastTimeAbsolute) {
// time seems to have run backwards - this can happen
// when the system time is adjusted, for example
// on a leap second
now = lastTimeAbsolute;
} else {
lastTimeAbsolute = now;
}
return now;
}
/**
* Apply the freed space to the chunk metadata. The metadata is updated, but
* completely free chunks are not removed from the set of chunks, and the
* disk space is not yet marked as free.
*/
private void applyFreedSpace() {
while (true) {
ArrayList modified = new ArrayList<>();
synchronized (freedPageSpace) {
for (Chunk f : freedPageSpace.values()) {
Chunk c = chunks.get(f.id);
if (c != null) { // skip if was already removed
c.maxLenLive += f.maxLenLive;
c.pageCountLive += f.pageCountLive;
if (c.pageCountLive < 0 && c.pageCountLive > -MARKED_FREE) {
// can happen after a rollback
c.pageCountLive = 0;
}
if (c.maxLenLive < 0 && c.maxLenLive > -MARKED_FREE) {
// can happen after a rollback
c.maxLenLive = 0;
}
modified.add(c);
}
}
freedPageSpace.clear();
}
if (modified.isEmpty()) {
break;
}
for (Chunk c : modified) {
meta.put(Chunk.getMetaKey(c.id), c.asString());
}
markMetaChanged();
}
}
/**
* Shrink the file if possible, and if at least a given percentage can be
* saved.
*
* @param minPercent the minimum percentage to save
*/
private void shrinkFileIfPossible(int minPercent) {
if (fileStore.isReadOnly()) {
return;
}
long end = getFileLengthInUse();
long fileSize = fileStore.size();
if (end >= fileSize) {
return;
}
if (minPercent > 0 && fileSize - end < BLOCK_SIZE) {
return;
}
int savedPercent = (int) (100 - (end * 100 / fileSize));
if (savedPercent < minPercent) {
return;
}
if (isOpenOrStopping()) {
sync();
}
fileStore.truncate(end);
}
/**
* Get the position right after the last used byte.
*
* @return the position
*/
private long getFileLengthInUse() {
long result = fileStore.getFileLengthInUse();
assert result == measureFileLengthInUse() : result + " != " + measureFileLengthInUse();
return result;
}
private long measureFileLengthInUse() {
long size = 2;
for (Chunk c : chunks.values()) {
if (c.len != Integer.MAX_VALUE) {
size = Math.max(size, c.block + c.len);
}
}
return size * BLOCK_SIZE;
}
/**
* Check whether there are any unsaved changes.
*
* @return if there are any changes
*/
public boolean hasUnsavedChanges() {
if (metaChanged) {
return true;
}
for (MVMap m : maps.values()) {
if (!m.isClosed()) {
if(m.hasChangesSince(lastStoredVersion)) {
return true;
}
}
}
return false;
}
private boolean hasUnsavedChangesInternal() {
if (meta.hasChangesSince(lastStoredVersion)) {
return true;
}
return hasUnsavedChanges();
}
private Chunk readChunkHeader(long block) {
long p = block * BLOCK_SIZE;
ByteBuffer buff = fileStore.readFully(p, Chunk.MAX_HEADER_LENGTH);
return Chunk.readChunkHeader(buff, p);
}
/**
* Compact the store by moving all live pages to new chunks.
*
* @return if anything was written
*/
public boolean compactRewriteFully() {
storeLock.lock();
try {
checkOpen();
if (lastChunk == null) {
// nothing to do
return false;
}
for (MVMap m : maps.values()) {
@SuppressWarnings("unchecked")
MVMap map = (MVMap) m;
Cursor cursor = map.cursor(null);
Page lastPage = null;
while (cursor.hasNext()) {
cursor.next();
Page p = cursor.getPage();
if (p == lastPage) {
continue;
}
Object k = p.getKey(0);
Object v = p.getValue(0);
map.put(k, v);
lastPage = p;
}
}
commit();
return true;
} finally {
storeLock.unlock();
}
}
/**
* Compact by moving all chunks next to each other.
*/
public void compactMoveChunks() {
compactMoveChunks(100, Long.MAX_VALUE);
}
/**
* Compact the store by moving all chunks next to each other, if there is
* free space between chunks. This might temporarily increase the file size.
* Chunks are overwritten irrespective of the current retention time. Before
* overwriting chunks and before resizing the file, syncFile() is called.
*
* @param targetFillRate do nothing if the file store fill rate is higher
* than this
* @param moveSize the number of bytes to move
*/
public void compactMoveChunks(int targetFillRate, long moveSize) {
storeLock.lock();
try {
checkOpen();
if (lastChunk != null && reuseSpace) {
int oldRetentionTime = retentionTime;
boolean oldReuse = reuseSpace;
try {
retentionTime = -1;
freeUnusedChunks(false);
if (fileStore.getFillRate() <= targetFillRate) {
long start = fileStore.getFirstFree() / BLOCK_SIZE;
ArrayList move = findChunksToMove(start, moveSize);
compactMoveChunks(move);
}
} finally {
reuseSpace = oldReuse;
retentionTime = oldRetentionTime;
}
}
} finally {
storeLock.unlock();
}
}
private ArrayList findChunksToMove(long startBlock, long moveSize) {
ArrayList move = new ArrayList<>();
for (Chunk c : chunks.values()) {
if (c.block > startBlock) {
move.add(c);
}
}
// sort by block
Collections.sort(move, new Comparator() {
@Override
public int compare(Chunk o1, Chunk o2) {
return Long.signum(o1.block - o2.block);
}
});
// find which is the last block to keep
int count = 0;
long size = 0;
for (Chunk c : move) {
long chunkSize = c.len * (long) BLOCK_SIZE;
size += chunkSize;
if (size > moveSize) {
break;
}
count++;
}
// move the first block (so the first gap is moved),
// and the one at the end (so the file shrinks)
while (move.size() > count && move.size() > 1) {
move.remove(1);
}
return move;
}
private void compactMoveChunks(ArrayList move) {
for (Chunk c : move) {
moveChunk(c, true);
}
// update the metadata (store at the end of the file)
reuseSpace = false;
commit();
sync();
Chunk chunk = this.lastChunk;
// now re-use the empty space
reuseSpace = true;
for (Chunk c : move) {
// ignore if already removed during the previous store operation
if (chunks.containsKey(c.id)) {
moveChunk(c, false);
}
}
// update the metadata (within the file)
commit();
sync();
if (chunks.containsKey(chunk.id)) {
moveChunk(chunk, false);
commit();
}
shrinkFileIfPossible(0);
sync();
}
private void moveChunk(Chunk c, boolean toTheEnd) {
WriteBuffer buff = getWriteBuffer();
long start = c.block * BLOCK_SIZE;
int length = c.len * BLOCK_SIZE;
buff.limit(length);
ByteBuffer readBuff = fileStore.readFully(start, length);
Chunk.readChunkHeader(readBuff, start);
int chunkHeaderLen = readBuff.position();
buff.position(chunkHeaderLen);
buff.put(readBuff);
long pos = allocateFileSpace(length, toTheEnd);
fileStore.free(start, length);
c.block = pos / BLOCK_SIZE;
c.next = 0;
buff.position(0);
c.writeChunkHeader(buff, chunkHeaderLen);
buff.position(length - Chunk.FOOTER_LENGTH);
buff.put(c.getFooterBytes());
buff.position(0);
write(pos, buff.getBuffer());
releaseWriteBuffer(buff);
meta.put(Chunk.getMetaKey(c.id), c.asString());
markMetaChanged();
}
private long allocateFileSpace(int length, boolean atTheEnd) {
long filePos;
if (atTheEnd) {
filePos = getFileLengthInUse();
fileStore.markUsed(filePos, length);
} else {
filePos = fileStore.allocate(length);
}
return filePos;
}
/**
* Force all stored changes to be written to the storage. The default
* implementation calls FileChannel.force(true).
*/
public void sync() {
checkOpen();
FileStore f = fileStore;
if (f != null) {
f.sync();
}
}
/**
* Try to increase the fill rate by re-writing partially full chunks. Chunks
* with a low number of live items are re-written.
*
* If the current fill rate is higher than the target fill rate, nothing is
* done.
*
* Please note this method will not necessarily reduce the file size, as
* empty chunks are not overwritten.
*
* Only data of open maps can be moved. For maps that are not open, the old
* chunk is still referenced. Therefore, it is recommended to open all maps
* before calling this method.
*
* @param targetFillRate the minimum percentage of live entries
* @param write the minimum number of bytes to write
* @return if a chunk was re-written
*/
public boolean compact(int targetFillRate, int write) {
if (!reuseSpace) {
return false;
}
checkOpen();
// We can't wait forever for the lock here,
// because if called from the background thread,
// it might go into deadlock with concurrent database closure
// and attempt to stop this thread.
try {
if (!storeLock.isHeldByCurrentThread() &&
storeLock.tryLock(10, TimeUnit.MILLISECONDS)) {
try {
ArrayList old = findOldChunks(targetFillRate, write);
if (old == null || old.isEmpty()) {
return false;
}
compactRewrite(old);
return true;
} finally {
storeLock.unlock();
}
}
return false;
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
/**
* Get the current fill rate (percentage of used space in the file). Unlike
* the fill rate of the store, here we only account for chunk data; the fill
* rate here is how much of the chunk data is live (still referenced). Young
* chunks are considered live.
*
* @return the fill rate, in percent (100 is completely full)
*/
public int getCurrentFillRate() {
long maxLengthSum = 1;
long maxLengthLiveSum = 1;
long time = getTimeSinceCreation();
for (Chunk c : chunks.values()) {
maxLengthSum += c.maxLen;
if (c.time + retentionTime > time) {
// young chunks (we don't optimize those):
// assume if they are fully live
// so that we don't try to optimize yet
// until they get old
maxLengthLiveSum += c.maxLen;
} else {
maxLengthLiveSum += c.maxLenLive;
}
}
// the fill rate of all chunks combined
if (maxLengthSum <= 0) {
// avoid division by 0
maxLengthSum = 1;
}
int fillRate = (int) (100 * maxLengthLiveSum / maxLengthSum);
return fillRate;
}
private ArrayList findOldChunks(int targetFillRate, int write) {
if (lastChunk == null) {
// nothing to do
return null;
}
long time = getTimeSinceCreation();
int fillRate = getCurrentFillRate();
if (fillRate >= targetFillRate) {
return null;
}
// the 'old' list contains the chunks we want to free up
ArrayList old = new ArrayList<>();
Chunk last = chunks.get(lastChunk.id);
for (Chunk c : chunks.values()) {
// only look at chunk older than the retention time
// (it's possible to compact chunks earlier, but right
// now we don't do that)
if (c.time + retentionTime <= time) {
long age = last.version - c.version + 1;
c.collectPriority = (int) (c.getFillRate() * 1000 / Math.max(1,age));
old.add(c);
}
}
if (old.isEmpty()) {
return null;
}
// sort the list, so the first entry should be collected first
Collections.sort(old, new Comparator() {
@Override
public int compare(Chunk o1, Chunk o2) {
int comp = Integer.compare(o1.collectPriority, o2.collectPriority);
if (comp == 0) {
comp = Long.compare(o1.maxLenLive, o2.maxLenLive);
}
return comp;
}
});
// find out up to were in the old list we need to move
long written = 0;
int chunkCount = 0;
Chunk move = null;
for (Chunk c : old) {
if (move != null) {
if (c.collectPriority > 0 && written > write) {
break;
}
}
written += c.maxLenLive;
chunkCount++;
move = c;
}
if (chunkCount < 1) {
return null;
}
// remove the chunks we want to keep from this list
boolean remove = false;
for (Iterator it = old.iterator(); it.hasNext();) {
Chunk c = it.next();
if (move == c) {
remove = true;
} else if (remove) {
it.remove();
}
}
return old;
}
private void compactRewrite(Iterable old) {
HashSet set = new HashSet<>();
for (Chunk c : old) {
set.add(c.id);
}
for (MVMap m : maps.values()) {
@SuppressWarnings("unchecked")
MVMap map = (MVMap) m;
if (!map.isClosed()) {
map.rewrite(set);
}
}
meta.rewrite(set);
freeUnusedChunks(false);
commit();
}
/**
* Read a page.
*
* @param map the map
* @param pos the page position
* @return the page
*/
Page readPage(MVMap map, long pos) {
if (!DataUtils.isPageSaved(pos)) {
throw DataUtils.newIllegalStateException(
DataUtils.ERROR_FILE_CORRUPT, "Position 0");
}
Page p = cache == null ? null : cache.get(pos);
if (p == null) {
ByteBuffer buff = readBufferForPage(pos, map.getId());
p = Page.read(buff, pos, map);
cachePage(p);
}
return p;
}
/**
* Remove a page.
*
* @param pos the position of the page
* @param memory the memory usage
*/
void removePage(long pos, int memory) {
// we need to keep temporary pages,
// to support reading old versions and rollback
if (!DataUtils.isPageSaved(pos)) {
// the page was not yet stored:
// just using "unsavedMemory -= memory" could result in negative
// values, because in some cases a page is allocated, but never
// stored, so we need to use max
unsavedMemory = Math.max(0, unsavedMemory - memory);
return;
}
int chunkId = DataUtils.getPageChunkId(pos);
// synchronize, because pages could be freed concurrently
synchronized (freedPageSpace) {
Chunk chunk = freedPageSpace.get(chunkId);
if (chunk == null) {
chunk = new Chunk(chunkId);
freedPageSpace.put(chunkId, chunk);
}
chunk.maxLenLive -= DataUtils.getPageMaxLength(pos);
chunk.pageCountLive -= 1;
}
}
Compressor getCompressorFast() {
if (compressorFast == null) {
compressorFast = new CompressLZF();
}
return compressorFast;
}
Compressor getCompressorHigh() {
if (compressorHigh == null) {
compressorHigh = new CompressDeflate();
}
return compressorHigh;
}
int getCompressionLevel() {
return compressionLevel;
}
public int getPageSplitSize() {
return pageSplitSize;
}
public int getKeysPerPage() {
return keysPerPage;
}
public long getMaxPageSize() {
return cache == null ? Long.MAX_VALUE : cache.getMaxItemSize() >> 4;
}
public boolean getReuseSpace() {
return reuseSpace;
}
/**
* Whether empty space in the file should be re-used. If enabled, old data
* is overwritten (default). If disabled, writes are appended at the end of
* the file.
*
* This setting is specially useful for online backup. To create an online
* backup, disable this setting, then copy the file (starting at the
* beginning of the file). In this case, concurrent backup and write
* operations are possible (obviously the backup process needs to be faster
* than the write operations).
*
* @param reuseSpace the new value
*/
public void setReuseSpace(boolean reuseSpace) {
this.reuseSpace = reuseSpace;
}
public int getRetentionTime() {
return retentionTime;
}
/**
* How long to retain old, persisted chunks, in milliseconds. Chunks that
* are older may be overwritten once they contain no live data.
*
* The default value is 45000 (45 seconds) when using the default file
* store. It is assumed that a file system and hard disk will flush all
* write buffers within this time. Using a lower value might be dangerous,
* unless the file system and hard disk flush the buffers earlier. To
* manually flush the buffers, use
* MVStore.getFile().force(true), however please note that
* according to various tests this does not always work as expected
* depending on the operating system and hardware.
*
* The retention time needs to be long enough to allow reading old chunks
* while traversing over the entries of a map.
*
* This setting is not persisted.
*
* @param ms how many milliseconds to retain old chunks (0 to overwrite them
* as early as possible)
*/
public void setRetentionTime(int ms) {
this.retentionTime = ms;
}
/**
* How many versions to retain for in-memory stores. If not set, 5 old
* versions are retained.
*
* @param count the number of versions to keep
*/
public void setVersionsToKeep(int count) {
this.versionsToKeep = count;
}
/**
* Get the oldest version to retain in memory (for in-memory stores).
*
* @return the version
*/
public long getVersionsToKeep() {
return versionsToKeep;
}
/**
* Get the oldest version to retain in memory, which is the manually set
* retain version, or the current store version (whatever is older).
*
* @return the version
*/
public long getOldestVersionToKeep() {
long v = oldestVersionToKeep.get();
if (fileStore == null) {
v = Math.max(v - versionsToKeep + 1, INITIAL_VERSION);
return v;
}
long storeVersion = currentStoreVersion;
if (storeVersion != INITIAL_VERSION && storeVersion < v) {
v = storeVersion;
}
return v;
}
private void setOldestVersionToKeep(long oldestVersionToKeep) {
boolean success;
do {
long current = this.oldestVersionToKeep.get();
// Oldest version may only advance, never goes back
success = oldestVersionToKeep <= current ||
this.oldestVersionToKeep.compareAndSet(current, oldestVersionToKeep);
} while (!success);
}
/**
* Check whether all data can be read from this version. This requires that
* all chunks referenced by this version are still available (not
* overwritten).
*
* @param version the version
* @return true if all data can be read
*/
private boolean isKnownVersion(long version) {
if (version > currentVersion || version < 0) {
return false;
}
if (version == currentVersion || chunks.isEmpty()) {
// no stored data
return true;
}
// need to check if a chunk for this version exists
Chunk c = getChunkForVersion(version);
if (c == null) {
return false;
}
// also, all chunks referenced by this version
// need to be available in the file
MVMap oldMeta = getMetaMap(version);
if (oldMeta == null) {
return false;
}
try {
for (Iterator it = oldMeta.keyIterator("chunk.");
it.hasNext();) {
String chunkKey = it.next();
if (!chunkKey.startsWith("chunk.")) {
break;
}
if (!meta.containsKey(chunkKey)) {
String s = oldMeta.get(chunkKey);
Chunk c2 = Chunk.fromString(s);
Chunk test = readChunkHeaderAndFooter(c2.block);
if (test == null || test.id != c2.id) {
return false;
}
}
}
} catch (IllegalStateException e) {
// the chunk missing where the metadata is stored
return false;
}
return true;
}
/**
* Increment the number of unsaved pages.
*
* @param memory the memory usage of the page
*/
public void registerUnsavedPage(int memory) {
unsavedMemory += memory;
int newValue = unsavedMemory;
if (newValue > autoCommitMemory && autoCommitMemory > 0) {
saveNeeded = true;
}
}
public boolean isSaveNeeded() {
return saveNeeded;
}
/**
* This method is called before writing to a map.
*
* @param map the map
*/
void beforeWrite(MVMap map) {
if (saveNeeded && fileStore != null && isOpenOrStopping()) {
saveNeeded = false;
// check again, because it could have been written by now
if (unsavedMemory > autoCommitMemory && autoCommitMemory > 0) {
// if unsaved memory creation rate is to high,
// some back pressure need to be applied
// to slow things down and avoid OOME
if (3 * unsavedMemory > 4 * autoCommitMemory) {
commit();
} else {
tryCommit();
}
}
}
}
/**
* Get the store version. The store version is usually used to upgrade the
* structure of the store after upgrading the application. Initially the
* store version is 0, until it is changed.
*
* @return the store version
*/
public int getStoreVersion() {
checkOpen();
String x = meta.get("setting.storeVersion");
return x == null ? 0 : DataUtils.parseHexInt(x);
}
/**
* Update the store version.
*
* @param version the new store version
*/
public void setStoreVersion(int version) {
storeLock.lock();
try {
checkOpen();
markMetaChanged();
meta.put("setting.storeVersion", Integer.toHexString(version));
} finally {
storeLock.unlock();
}
}
/**
* Revert to the beginning of the current version, reverting all uncommitted
* changes.
*/
public void rollback() {
rollbackTo(currentVersion);
}
/**
* Revert to the beginning of the given version. All later changes (stored
* or not) are forgotten. All maps that were created later are closed. A
* rollback to a version before the last stored version is immediately
* persisted. Rollback to version 0 means all data is removed.
*
* @param version the version to revert to
*/
public void rollbackTo(long version) {
storeLock.lock();
try {
checkOpen();
if (version == 0) {
// special case: remove all data
for (MVMap m : maps.values()) {
m.close();
}
meta.setInitialRoot(meta.createEmptyLeaf(), INITIAL_VERSION);
chunks.clear();
if (fileStore != null) {
fileStore.clear();
}
maps.clear();
lastChunk = null;
synchronized (freedPageSpace) {
freedPageSpace.clear();
}
versions.clear();
currentVersion = version;
setWriteVersion(version);
metaChanged = false;
lastStoredVersion = INITIAL_VERSION;
return;
}
DataUtils.checkArgument(
isKnownVersion(version),
"Unknown version {0}", version);
for (MVMap m : maps.values()) {
m.rollbackTo(version);
}
TxCounter txCounter;
while ((txCounter = versions.peekLast()) != null && txCounter.version >= version) {
versions.removeLast();
}
currentTxCounter = new TxCounter(version);
meta.rollbackTo(version);
metaChanged = false;
boolean loadFromFile = false;
// find out which chunks to remove,
// and which is the newest chunk to keep
// (the chunk list can have gaps)
ArrayList remove = new ArrayList<>();
Chunk keep = null;
for (Chunk c : chunks.values()) {
if (c.version > version) {
remove.add(c.id);
} else if (keep == null || keep.id < c.id) {
keep = c;
}
}
if (!remove.isEmpty()) {
// remove the youngest first, so we don't create gaps
// (in case we remove many chunks)
Collections.sort(remove, Collections.reverseOrder());
loadFromFile = true;
for (int id : remove) {
Chunk c = chunks.remove(id);
long start = c.block * BLOCK_SIZE;
int length = c.len * BLOCK_SIZE;
fileStore.free(start, length);
assert fileStore.getFileLengthInUse() == measureFileLengthInUse() :
fileStore.getFileLengthInUse() + " != " + measureFileLengthInUse();
// overwrite the chunk,
// so it is not be used later on
WriteBuffer buff = getWriteBuffer();
buff.limit(length);
// buff.clear() does not set the data
Arrays.fill(buff.getBuffer().array(), (byte) 0);
write(start, buff.getBuffer());
releaseWriteBuffer(buff);
// only really needed if we remove many chunks, when writes are
// re-ordered - but we do it always, because rollback is not
// performance critical
sync();
}
lastChunk = keep;
writeStoreHeader();
readStoreHeader();
}
for (MVMap m : new ArrayList<>(maps.values())) {
int id = m.getId();
if (m.getCreateVersion() >= version) {
m.close();
maps.remove(id);
} else {
if (loadFromFile) {
m.setRootPos(getRootPos(meta, id), version);
} else {
m.rollbackRoot(version);
}
}
}
currentVersion = version;
if (lastStoredVersion == INITIAL_VERSION) {
lastStoredVersion = currentVersion - 1;
}
} finally {
storeLock.unlock();
}
}
private static long getRootPos(MVMap map, int mapId) {
String root = map.get(MVMap.getMapRootKey(mapId));
return root == null ? 0 : DataUtils.parseHexLong(root);
}
/**
* Get the current version of the data. When a new store is created, the
* version is 0.
*
* @return the version
*/
public long getCurrentVersion() {
return currentVersion;
}
public long getLastStoredVersion() {
return lastStoredVersion;
}
/**
* Get the file store.
*
* @return the file store
*/
public FileStore getFileStore() {
return fileStore;
}
/**
* Get the store header. This data is for informational purposes only. The
* data is subject to change in future versions. The data should not be
* modified (doing so may corrupt the store).
*
* @return the store header
*/
public Map getStoreHeader() {
return storeHeader;
}
private void checkOpen() {
if (!isOpenOrStopping()) {
throw DataUtils.newIllegalStateException(DataUtils.ERROR_CLOSED,
"This store is closed", panicException);
}
}
/**
* Rename a map.
*
* @param map the map
* @param newName the new name
*/
public void renameMap(MVMap map, String newName) {
checkOpen();
DataUtils.checkArgument(map != meta,
"Renaming the meta map is not allowed");
int id = map.getId();
String oldName = getMapName(id);
if (oldName != null && !oldName.equals(newName)) {
String idHexStr = Integer.toHexString(id);
// at first create a new name as an "alias"
String existingIdHexStr = meta.putIfAbsent("name." + newName, idHexStr);
// we need to cope with the case of previously unfinished rename
DataUtils.checkArgument(
existingIdHexStr == null || existingIdHexStr.equals(idHexStr),
"A map named {0} already exists", newName);
// switch roles of a new and old names - old one is an alias now
meta.put(MVMap.getMapKey(id), map.asString(newName));
// get rid of the old name completely
meta.remove("name." + oldName);
markMetaChanged();
}
}
/**
* Remove a map. Please note rolling back this operation does not restore
* the data; if you need this ability, use Map.clear().
*
* @param map the map to remove
*/
public void removeMap(MVMap map) {
removeMap(map, true);
}
/**
* Remove a map.
*
* @param map the map to remove
* @param delayed whether to delay deleting the metadata
*/
public void removeMap(MVMap map, boolean delayed) {
storeLock.lock();
try {
checkOpen();
DataUtils.checkArgument(map != meta,
"Removing the meta map is not allowed");
map.close();
RootReference rootReference = map.getRoot();
updateCounter += rootReference.updateCounter;
updateAttemptCounter += rootReference.updateAttemptCounter;
int id = map.getId();
String name = getMapName(id);
removeMap(name, id, delayed);
} finally {
storeLock.unlock();
}
}
private void removeMap(String name, int id, boolean delayed) {
if (meta.remove(MVMap.getMapKey(id)) != null) {
markMetaChanged();
}
if (meta.remove("name." + name) != null) {
markMetaChanged();
}
if (!delayed) {
if (meta.remove(MVMap.getMapRootKey(id)) != null) {
markMetaChanged();
}
maps.remove(id);
}
}
/**
* Remove map by name.
*
* @param name the map name
*/
public void removeMap(String name) {
int id = getMapId(name);
if(id > 0) {
removeMap(name, id, false);
}
}
/**
* Get the name of the given map.
*
* @param id the map id
* @return the name, or null if not found
*/
public String getMapName(int id) {
checkOpen();
String m = meta.get(MVMap.getMapKey(id));
return m == null ? null : DataUtils.getMapName(m);
}
private int getMapId(String name) {
String m = meta.get("name." + name);
return m == null ? -1 : DataUtils.parseHexInt(m);
}
/**
* Commit and save all changes, if there are any, and compact the store if
* needed.
*/
void writeInBackground() {
try {
if (!isOpenOrStopping()) {
return;
}
// could also commit when there are many unsaved pages,
// but according to a test it doesn't really help
long time = getTimeSinceCreation();
if (time <= lastCommitTime + autoCommitDelay) {
return;
}
tryCommit();
if (autoCompactFillRate > 0) {
// whether there were file read or write operations since
// the last time
boolean fileOps;
long fileOpCount = fileStore.getWriteCount() + fileStore.getReadCount();
if (autoCompactLastFileOpCount != fileOpCount) {
fileOps = true;
} else {
fileOps = false;
}
// use a lower fill rate if there were any file operations
int targetFillRate = fileOps ? autoCompactFillRate / 3 : autoCompactFillRate;
compact(targetFillRate, autoCommitMemory);
autoCompactLastFileOpCount = fileStore.getWriteCount() + fileStore.getReadCount();
}
} catch (Throwable e) {
handleException(e);
}
}
private void handleException(Throwable ex) {
if (backgroundExceptionHandler != null) {
try {
backgroundExceptionHandler.uncaughtException(Thread.currentThread(), ex);
} catch(Throwable ignore) {
if (ex != ignore) { // OOME may be the same
ex.addSuppressed(ignore);
}
}
}
}
/**
* Set the read cache size in MB.
*
* @param mb the cache size in MB.
*/
public void setCacheSize(int mb) {
final long bytes = (long) mb * 1024 * 1024;
if (cache != null) {
cache.setMaxMemory(bytes);
cache.clear();
}
if (cacheChunkRef != null) {
cacheChunkRef.setMaxMemory(bytes / 4);
cacheChunkRef.clear();
}
}
private boolean isOpen() {
return state == STATE_OPEN;
}
/**
* Determine that store is open, or wait for it to be closed (by other thread)
* @return true if store is open, false otherwise
*/
public boolean isClosed() {
if (isOpen()) {
return false;
}
storeLock.lock();
try {
assert state == STATE_CLOSED;
return true;
} finally {
storeLock.unlock();
}
}
private boolean isOpenOrStopping() {
return state <= STATE_STOPPING;
}
private void stopBackgroundThread(boolean waitForIt) {
// Loop here is not strictly necessary, except for case of a spurious failure,
// which should not happen with non-weak flavour of CAS operation,
// but I've seen it, so just to be safe...
BackgroundWriterThread t;
while ((t = backgroundWriterThread.get()) != null) {
if (backgroundWriterThread.compareAndSet(t, null)) {
// if called from within the thread itself - can not join
if (t != Thread.currentThread()) {
synchronized (t.sync) {
t.sync.notifyAll();
}
if (waitForIt) {
try {
t.join();
} catch (Exception e) {
// ignore
}
}
}
break;
}
}
}
/**
* Set the maximum delay in milliseconds to auto-commit changes.
*
* To disable auto-commit, set the value to 0. In this case, changes are
* only committed when explicitly calling commit.
*
* The default is 1000, meaning all changes are committed after at most one
* second.
*
* @param millis the maximum delay
*/
public void setAutoCommitDelay(int millis) {
if (autoCommitDelay == millis) {
return;
}
autoCommitDelay = millis;
if (fileStore == null || fileStore.isReadOnly()) {
return;
}
stopBackgroundThread(true);
// start the background thread if needed
if (millis > 0 && isOpen()) {
int sleep = Math.max(1, millis / 10);
BackgroundWriterThread t =
new BackgroundWriterThread(this, sleep,
fileStore.toString());
if (backgroundWriterThread.compareAndSet(null, t)) {
t.start();
}
}
}
boolean isBackgroundThread() {
return Thread.currentThread() == backgroundWriterThread.get();
}
/**
* Get the auto-commit delay.
*
* @return the delay in milliseconds, or 0 if auto-commit is disabled.
*/
public int getAutoCommitDelay() {
return autoCommitDelay;
}
/**
* Get the maximum memory (in bytes) used for unsaved pages. If this number
* is exceeded, unsaved changes are stored to disk.
*
* @return the memory in bytes
*/
public int getAutoCommitMemory() {
return autoCommitMemory;
}
/**
* Get the estimated memory (in bytes) of unsaved data. If the value exceeds
* the auto-commit memory, the changes are committed.
*
* The returned value is an estimation only.
*
* @return the memory in bytes
*/
public int getUnsavedMemory() {
return unsavedMemory;
}
/**
* Put the page in the cache.
* @param page the page
*/
void cachePage(Page page) {
if (cache != null) {
cache.put(page.getPos(), page, page.getMemory());
}
}
/**
* Get the amount of memory used for caching, in MB.
* Note that this does not include the page chunk references cache, which is
* 25% of the size of the page cache.
*
* @return the amount of memory used for caching
*/
public int getCacheSizeUsed() {
if (cache == null) {
return 0;
}
return (int) (cache.getUsedMemory() >> 20);
}
/**
* Get the maximum cache size, in MB.
* Note that this does not include the page chunk references cache, which is
* 25% of the size of the page cache.
*
* @return the cache size
*/
public int getCacheSize() {
if (cache == null) {
return 0;
}
return (int) (cache.getMaxMemory() >> 20);
}
/**
* Get the cache.
*
* @return the cache
*/
public CacheLongKeyLIRS getCache() {
return cache;
}
/**
* Whether the store is read-only.
*
* @return true if it is
*/
public boolean isReadOnly() {
return fileStore != null && fileStore.isReadOnly();
}
public double getUpdateFailureRatio() {
long updateCounter = this.updateCounter;
long updateAttemptCounter = this.updateAttemptCounter;
RootReference rootReference = meta.getRoot();
updateCounter += rootReference.updateCounter;
updateAttemptCounter += rootReference.updateAttemptCounter;
for (MVMap map : maps.values()) {
RootReference root = map.getRoot();
updateCounter += root.updateCounter;
updateAttemptCounter += root.updateAttemptCounter;
}
return updateAttemptCounter == 0 ? 0 : 1 - ((double)updateCounter / updateAttemptCounter);
}
/**
* Register opened operation (transaction).
* This would increment usage counter for the current version.
* This version (and all after it) should not be dropped until all
* transactions involved are closed and usage counter goes to zero.
* @return TxCounter to be decremented when operation finishes (transaction closed).
*/
public TxCounter registerVersionUsage() {
TxCounter txCounter;
while(true) {
txCounter = currentTxCounter;
if(txCounter.counter.getAndIncrement() >= 0) {
break;
}
// The only way for counter to be negative
// if it was retrieved right before onVersionChange()
// and now onVersionChange() is done.
// This version is eligible for reclamation now
// and should not be used here, so restore count
// not to upset accounting and try again with a new
// version (currentTxCounter should have changed).
assert txCounter != currentTxCounter : txCounter;
txCounter.counter.decrementAndGet();
}
return txCounter;
}
/**
* De-register (close) completed operation (transaction).
* This will decrement usage counter for the corresponding version.
* If counter reaches zero, that version (and all unused after it)
* can be dropped immediately.
*
* @param txCounter to be decremented, obtained from registerVersionUsage()
*/
public void deregisterVersionUsage(TxCounter txCounter) {
if(txCounter != null) {
if(txCounter.counter.decrementAndGet() <= 0) {
if (!storeLock.isHeldByCurrentThread() && storeLock.tryLock()) {
try {
dropUnusedVersions();
} finally {
storeLock.unlock();
}
}
}
}
}
private void onVersionChange(long version) {
TxCounter txCounter = this.currentTxCounter;
assert txCounter.counter.get() >= 0;
versions.add(txCounter);
currentTxCounter = new TxCounter(version);
txCounter.counter.decrementAndGet();
dropUnusedVersions();
}
private void dropUnusedVersions() {
TxCounter txCounter;
while ((txCounter = versions.peek()) != null
&& txCounter.counter.get() < 0) {
versions.poll();
}
setOldestVersionToKeep(txCounter != null ? txCounter.version : currentTxCounter.version);
}
/**
* Class TxCounter is a simple data structure to hold version of the store
* along with the counter of open transactions,
* which are still operating on this version.
*/
public static final class TxCounter {
/**
* Version of a store, this TxCounter is related to
*/
public final long version;
/**
* Counter of outstanding operation on this version of a store
*/
public final AtomicInteger counter = new AtomicInteger();
TxCounter(long version) {
this.version = version;
}
@Override
public String toString() {
return "v=" + version + " / cnt=" + counter;
}
}
/**
* A background writer thread to automatically store changes from time to
* time.
*/
private static class BackgroundWriterThread extends Thread {
public final Object sync = new Object();
private final MVStore store;
private final int sleep;
BackgroundWriterThread(MVStore store, int sleep, String fileStoreName) {
super("MVStore background writer " + fileStoreName);
this.store = store;
this.sleep = sleep;
setDaemon(true);
}
@Override
public void run() {
while (store.isBackgroundThread()) {
synchronized (sync) {
try {
sync.wait(sleep);
} catch (InterruptedException ignore) {
}
}
if (!store.isBackgroundThread()) {
break;
}
store.writeInBackground();
}
}
}
/**
* A builder for an MVStore.
*/
public static final class Builder {
private final HashMap config;
private Builder(HashMap config) {
this.config = config;
}
/**
* Creates new instance of MVStore.Builder.
*/
public Builder() {
config = new HashMap<>();
}
private Builder set(String key, Object value) {
config.put(key, value);
return this;
}
/**
* Disable auto-commit, by setting the auto-commit delay and auto-commit
* buffer size to 0.
*
* @return this
*/
public Builder autoCommitDisabled() {
// we have a separate config option so that
// no thread is started if the write delay is 0
// (if we only had a setter in the MVStore,
// the thread would need to be started in any case)
//set("autoCommitBufferSize", 0);
return set("autoCommitDelay", 0);
}
/**
* Set the size of the write buffer, in KB disk space (for file-based
* stores). Unless auto-commit is disabled, changes are automatically
* saved if there are more than this amount of changes.
*
* The default is 1024 KB.
*
* When the value is set to 0 or lower, data is not automatically
* stored.
*
* @param kb the write buffer size, in kilobytes
* @return this
*/
public Builder autoCommitBufferSize(int kb) {
return set("autoCommitBufferSize", kb);
}
/**
* Set the auto-compact target fill rate. If the average fill rate (the
* percentage of the storage space that contains active data) of the
* chunks is lower, then the chunks with a low fill rate are re-written.
* Also, if the percentage of empty space between chunks is higher than
* this value, then chunks at the end of the file are moved. Compaction
* stops if the target fill rate is reached.
*
* The default value is 40 (40%). The value 0 disables auto-compacting.
*
*
* @param percent the target fill rate
* @return this
*/
public Builder autoCompactFillRate(int percent) {
return set("autoCompactFillRate", percent);
}
/**
* Use the following file name. If the file does not exist, it is
* automatically created. The parent directory already must exist.
*
* @param fileName the file name
* @return this
*/
public Builder fileName(String fileName) {
return set("fileName", fileName);
}
/**
* Encrypt / decrypt the file using the given password. This method has
* no effect for in-memory stores. The password is passed as a
* char array so that it can be cleared as soon as possible. Please note
* there is still a small risk that password stays in memory (due to
* Java garbage collection). Also, the hashed encryption key is kept in
* memory as long as the file is open.
*
* @param password the password
* @return this
*/
public Builder encryptionKey(char[] password) {
return set("encryptionKey", password);
}
/**
* Open the file in read-only mode. In this case, a shared lock will be
* acquired to ensure the file is not concurrently opened in write mode.
*
* If this option is not used, the file is locked exclusively.
*
* Please note a store may only be opened once in every JVM (no matter
* whether it is opened in read-only or read-write mode), because each
* file may be locked only once in a process.
*
* @return this
*/
public Builder readOnly() {
return set("readOnly", 1);
}
/**
* Set the read cache size in MB. The default is 16 MB.
*
* @param mb the cache size in megabytes
* @return this
*/
public Builder cacheSize(int mb) {
return set("cacheSize", mb);
}
/**
* Set the read cache concurrency. The default is 16, meaning 16
* segments are used.
*
* @param concurrency the cache concurrency
* @return this
*/
public Builder cacheConcurrency(int concurrency) {
return set("cacheConcurrency", concurrency);
}
/**
* Compress data before writing using the LZF algorithm. This will save
* about 50% of the disk space, but will slow down read and write
* operations slightly.
*
* This setting only affects writes; it is not necessary to enable
* compression when reading, even if compression was enabled when
* writing.
*
* @return this
*/
public Builder compress() {
return set("compress", 1);
}
/**
* Compress data before writing using the Deflate algorithm. This will
* save more disk space, but will slow down read and write operations
* quite a bit.
*
* This setting only affects writes; it is not necessary to enable
* compression when reading, even if compression was enabled when
* writing.
*
* @return this
*/
public Builder compressHigh() {
return set("compress", 2);
}
/**
* Set the amount of memory a page should contain at most, in bytes,
* before it is split. The default is 16 KB for persistent stores and 4
* KB for in-memory stores. This is not a limit in the page size, as
* pages with one entry can get larger. It is just the point where pages
* that contain more than one entry are split.
*
* @param pageSplitSize the page size
* @return this
*/
public Builder pageSplitSize(int pageSplitSize) {
return set("pageSplitSize", pageSplitSize);
}
/**
* Set the listener to be used for exceptions that occur when writing in
* the background thread.
*
* @param exceptionHandler the handler
* @return this
*/
public Builder backgroundExceptionHandler(
Thread.UncaughtExceptionHandler exceptionHandler) {
return set("backgroundExceptionHandler", exceptionHandler);
}
/**
* Use the provided file store instead of the default one.
*
* File stores passed in this way need to be open. They are not closed
* when closing the store.
*
* Please note that any kind of store (including an off-heap store) is
* considered a "persistence", while an "in-memory store" means objects
* are not persisted and fully kept in the JVM heap.
*
* @param store the file store
* @return this
*/
public Builder fileStore(FileStore store) {
return set("fileStore", store);
}
/**
* Open the store.
*
* @return the opened store
*/
public MVStore open() {
return new MVStore(config);
}
@Override
public String toString() {
return DataUtils.appendMap(new StringBuilder(), config).toString();
}
/**
* Read the configuration from a string.
*
* @param s the string representation
* @return the builder
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
public static Builder fromString(String s) {
// Cast from HashMap to HashMap is safe
return new Builder((HashMap) DataUtils.parseMap(s));
}
}
}