com.btoddb.fastpersitentqueue.MemorySegment Maven / Gradle / Ivy
package com.btoddb.fastpersitentqueue;
/*
* #%L
* fast-persistent-queue
* %%
* Copyright (C) 2014 btoddb.com
* %%
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
* #L%
*/
import com.btoddb.fastpersitentqueue.exceptions.FpqMemorySegmentOffline;
import com.btoddb.fastpersitentqueue.exceptions.FpqPushFinished;
import com.btoddb.fastpersitentqueue.exceptions.FpqSegmentNotInReadyState;
import com.eaio.uuid.UUID;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
*
*/
public class MemorySegment implements Comparable {
private static final Logger logger = LoggerFactory.getLogger(MemorySegment.class);
enum Status {
READY, SAVING, LOADING, OFFLINE, REMOVING
}
public static final int VERSION = 1;
private int version = VERSION;
private UUID id;
private long maxSizeInBytes = 10000000;
private volatile Status status;
private volatile boolean pushingFinished;
// these are so only one thread kicks of a load, remove, or page-to-disk
private AtomicBoolean removerTestAndSet = new AtomicBoolean(true);
private ReentrantReadWriteLock metaDataLock = new ReentrantReadWriteLock();
private ConcurrentSkipListMap queue = new ConcurrentSkipListMap();
private AtomicLong sizeInBytes = new AtomicLong();
private AtomicLong numberOfEntries = new AtomicLong();
private AtomicLong numberOfOnlineEntries = new AtomicLong();
private AtomicLong totalEventsPushed = new AtomicLong();
private AtomicLong totalEventsPopped = new AtomicLong();
private long entryListOffsetOnDisk;
// push is thread safe because ConcurrentSkipListMap says so
// true = push success
// false = not enough room and marked as finished
public boolean push(Collection events, long spaceRequired) throws FpqPushFinished {
// claim some room in this segment - if enough, then append entries and return
// if not enough room in this segment, no attempt is made to push the partial batch and
// this segment will be "push finished" regardless of how much room is available
metaDataLock.readLock().lock();
try {
if (!isPushingFinished() && Status.READY == status && sizeInBytes.addAndGet(spaceRequired) <= maxSizeInBytes) {
for (FpqEntry entry : events) {
queue.put(entry.getId(), entry);
}
totalEventsPushed.addAndGet(events.size());
// this must be done last as it signals when events are ready to be popped from this segment
numberOfEntries.addAndGet(events.size());
numberOfOnlineEntries.addAndGet(events.size());
return true;
}
}
finally {
metaDataLock.readLock().unlock();
}
// if got here, then not enough room to push *all* entries, so mark as finished
// TODO:BTB - maybe should use sync section to reduce waiting on meta data write lock?
metaDataLock.writeLock().lock();
try {
if (!isPushingFinished() && Status.READY == status) {
// only one thread will set to true and throw exception. the intent is that the segment
// manager thread that catches exception should check for things like (should i page to disk, etc)
setPushingFinished(true);
throw new FpqPushFinished();
}
}
finally {
metaDataLock.writeLock().unlock();
}
return false;
}
public Collection pop(int batchSize) throws FpqSegmentNotInReadyState {
metaDataLock.readLock().lock();
try {
// segment must be in READY state
if (Status.READY != status) {
throw new FpqSegmentNotInReadyState();
}
// find out if enough data remains in the segment. if this segment has been removed, paged
// to disk, etc, the adjustment will detect that too
long remaining = numberOfOnlineEntries.addAndGet(-batchSize);
int available = batchSize + (int) remaining;
// if > 0 then we have a good segment, so pop from it!
if (available > 0) {
// adjust for partial batch
if (remaining < 0) {
// don't just set to zero, many other threads are doing the same thing
numberOfOnlineEntries.addAndGet(-remaining);
}
else {
available = batchSize;
}
// we don't adjust number of available entries here. it should have been adjusted
// prior to popping to prevent unnecessary locking and still be thread-safe. by the time
// a thread gets here it should already know it had enough entries to pop 'batchSize' amount
ArrayList entryList = new ArrayList(batchSize);
long size = 0;
Map.Entry entry;
while (entryList.size() < available && null != (entry=queue.pollFirstEntry())) {
entryList.add(entry.getValue());
size += entry.getValue().getMemorySize();
}
sizeInBytes.addAndGet(-size);
numberOfEntries.addAndGet(-entryList.size());
totalEventsPopped.addAndGet(entryList.size());
return !entryList.isEmpty() ? entryList : null;
}
else {
// means not even a single event can be popped (for whatever reason), so put back the way we found it
numberOfOnlineEntries.addAndGet(batchSize);
return null;
}
}
finally {
metaDataLock.readLock().unlock();
}
}
public void clearQueue() {
queue.clear();
}
public boolean removerTestAndSet() {
return removerTestAndSet.compareAndSet(true, false);
}
public boolean isEntryQueued(FpqEntry entry) throws FpqMemorySegmentOffline {
if (Status.OFFLINE != status) {
return null != queue && queue.containsKey(entry.getId());
}
else {
throw new FpqMemorySegmentOffline();
}
}
public boolean shouldBeRemoved() {
metaDataLock.writeLock().lock();
try {
// if pushing finished, then schedule segment to be removed. seg.removerTestAndSet insures
// that only one thread will schedule the remove - so make sure it is last in the conditionals
if (isPushingFinished() && getNumberOfEntries() == 0 && removerTestAndSet()) {
logger.debug("removing segment {} because its empty and pushing has finished", getId().toString());
setStatus(MemorySegment.Status.REMOVING);
return true;
}
return false;
}
finally {
metaDataLock.writeLock().unlock();
}
}
public void writeToDisk(RandomAccessFile raFile) throws IOException {
writeHeaderToDisk(raFile);
for (FpqEntry entry : getQueue().values()) {
entry.writeToPaging(raFile);
}
}
private void writeHeaderToDisk(RandomAccessFile raFile) throws IOException {
Utils.writeInt(raFile, getVersion());
Utils.writeUuidToFile(raFile, id);
Utils.writeLong(raFile, maxSizeInBytes);
Utils.writeLong(raFile, getNumberOfEntries());
Utils.writeLong(raFile, sizeInBytes.get());
Utils.writeLong(raFile, totalEventsPushed.get());
Utils.writeLong(raFile, totalEventsPopped.get());
entryListOffsetOnDisk = raFile.getFilePointer();
}
public void readFromPagingFile(RandomAccessFile raFile) throws IOException {
readHeaderFromDisk(raFile);
numberOfOnlineEntries.set(numberOfEntries.get());
for ( int i=0;i < numberOfEntries.get();i++ ) {
FpqEntry entry = new FpqEntry();
entry.readFromPaging(raFile);
queue.put(entry.getId(), entry);
}
}
public void readHeaderFromDisk(RandomAccessFile raFile) throws IOException {
version = raFile.readInt();
id = Utils.readUuidFromFile(raFile);
maxSizeInBytes = Utils.readLong(raFile);
numberOfEntries.set(Utils.readLong(raFile));
sizeInBytes.set(Utils.readLong(raFile));
totalEventsPushed.set(Utils.readLong(raFile));
totalEventsPopped.set(Utils.readLong(raFile));
entryListOffsetOnDisk = raFile.getFilePointer();
}
public Status getStatus() {
return status;
}
public void setStatus(Status status) {
metaDataLock.writeLock().lock();
try {
this.status = status;
}
finally {
metaDataLock.writeLock().unlock();
}
}
public int getVersion() {
return version;
}
public UUID getId() {
return id;
}
public void setId(UUID id) {
this.id = id;
}
public long getMaxSizeInBytes() {
return maxSizeInBytes;
}
public void setMaxSizeInBytes(long maxSizeInBytes) {
this.maxSizeInBytes = maxSizeInBytes;
}
public long getNumberOfEntries() {
return numberOfEntries.get();
}
public long getNumberOfOnlineEntries() {
return numberOfOnlineEntries.get();
}
public long getEntryListOffsetOnDisk() {
return entryListOffsetOnDisk;
}
public boolean isPushingFinished() {
return pushingFinished;
}
public void setPushingFinished(boolean pushingFinished) {
metaDataLock.writeLock().lock();
try {
this.pushingFinished = pushingFinished;
}
finally {
metaDataLock.writeLock().unlock();
}
}
public ConcurrentSkipListMap getQueue() {
return queue;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
MemorySegment segment = (MemorySegment) o;
if (id != null ? !id.equals(segment.id) : segment.id != null) {
return false;
}
return true;
}
@Override
public int hashCode() {
return id != null ? id.hashCode() : 0;
}
@Override
public int compareTo(MemorySegment o2) {
// time based UUIDs
return id.compareTo(o2.getId());
}
@Override
public String toString() {
return "MemorySegment{" +
"id=" + id +
", status=" + status +
", pushingFinished=" + pushingFinished +
", sizeInBytes=" + sizeInBytes +
", numberOfEntries=" + numberOfEntries +
", numberOfOnlineEntries=" + numberOfOnlineEntries +
", totalEventsPushed=" + totalEventsPushed +
", totalEventsPopped=" + totalEventsPopped +
", entryListOffsetOnDisk=" + entryListOffsetOnDisk +
", queue size=" + (null != queue ? queue.size() : "null") +
'}';
}
}
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