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* Licensed to the Apache Software Foundation (ASF) under one
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.wal;
import static org.apache.commons.lang3.StringUtils.isNumeric;
import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.regionserver.wal.CompressionContext;
import org.apache.hadoop.hbase.regionserver.wal.FailedLogCloseException;
import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
import org.apache.hadoop.hbase.regionserver.wal.WALCoprocessorHost;
import org.apache.hadoop.hbase.replication.regionserver.WALFileLengthProvider;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.yetus.audience.InterfaceStability;
/**
* A Write Ahead Log (WAL) provides service for reading, writing waledits. This interface provides
* APIs for WAL users (such as RegionServer) to use the WAL (do append, sync, etc). Note that some
* internals, such as log rolling and performance evaluation tools, will use WAL.equals to determine
* if they have already seen a given WAL.
*/
@InterfaceAudience.Private
@InterfaceStability.Evolving
public interface WAL extends Closeable, WALFileLengthProvider {
/**
* Registers WALActionsListener
*/
void registerWALActionsListener(final WALActionsListener listener);
/**
* Unregisters WALActionsListener
*/
boolean unregisterWALActionsListener(final WALActionsListener listener);
/**
* Roll the log writer. That is, start writing log messages to a new file.
*
* The implementation is synchronized in order to make sure there's one rollWriter running at any
* given time.
* @return If lots of logs, flush the stores of returned regions so next time through we can clean
* logs. Returns null if nothing to flush. Names are actual region names as returned by
* {@link RegionInfo#getEncodedName()}
*/
Map> rollWriter() throws FailedLogCloseException, IOException;
/**
* Roll the log writer. That is, start writing log messages to a new file.
*
* The implementation is synchronized in order to make sure there's one rollWriter running at any
* given time. If true, force creation of a new writer even if no entries have been written to the
* current writer
* @return If lots of logs, flush the stores of returned regions so next time through we can clean
* logs. Returns null if nothing to flush. Names are actual region names as returned by
* {@link RegionInfo#getEncodedName()}
*/
Map> rollWriter(boolean force) throws IOException;
/**
* Stop accepting new writes. If we have unsynced writes still in buffer, sync them. Extant edits
* are left in place in backing storage to be replayed later.
*/
void shutdown() throws IOException;
/**
* Caller no longer needs any edits from this WAL. Implementers are free to reclaim underlying
* resources after this call; i.e. filesystem based WALs can archive or delete files.
*/
@Override
void close() throws IOException;
/**
* Append a set of data edits to the WAL. 'Data' here means that the content in the edits will
* also have transitioned through the memstore.
*
* The WAL is not flushed/sync'd after this transaction completes BUT on return this edit must
* have its region edit/sequence id assigned else it messes up our unification of mvcc and
* sequenceid. On return key will have the region edit/sequence id filled in.
* @param info the regioninfo associated with append
* @param key Modified by this call; we add to it this edits region edit/sequence id.
* @param edits Edits to append. MAY CONTAIN NO EDITS for case where we want to get an edit
* sequence id that is after all currently appended edits.
* @return Returns a 'transaction id' and key will have the region edit/sequence id
* in it.
* @see #appendMarker(RegionInfo, WALKeyImpl, WALEdit)
*/
long appendData(RegionInfo info, WALKeyImpl key, WALEdit edits) throws IOException;
/**
* Append an operational 'meta' event marker edit to the WAL. A marker meta edit could be a
* FlushDescriptor, a compaction marker, or a region event marker; e.g. region open or region
* close. The difference between a 'marker' append and a 'data' append as in
* {@link #appendData(RegionInfo, WALKeyImpl, WALEdit)}is that a marker will not have transitioned
* through the memstore.
*
* The WAL is not flushed/sync'd after this transaction completes BUT on return this edit must
* have its region edit/sequence id assigned else it messes up our unification of mvcc and
* sequenceid. On return key will have the region edit/sequence id filled in.
* @param info the regioninfo associated with append
* @param key Modified by this call; we add to it this edits region edit/sequence id.
* @param edits Edits to append. MAY CONTAIN NO EDITS for case where we want to get an edit
* sequence id that is after all currently appended edits.
* @return Returns a 'transaction id' and key will have the region edit/sequence id
* in it.
* @see #appendData(RegionInfo, WALKeyImpl, WALEdit)
*/
long appendMarker(RegionInfo info, WALKeyImpl key, WALEdit edits) throws IOException;
/**
* updates the seuence number of a specific store. depending on the flag: replaces current seq
* number if the given seq id is bigger, or even if it is lower than existing one
*/
void updateStore(byte[] encodedRegionName, byte[] familyName, Long sequenceid,
boolean onlyIfGreater);
/**
* Sync what we have in the WAL.
*/
void sync() throws IOException;
/**
* Sync the WAL if the txId was not already sync'd.
* @param txid Transaction id to sync to.
*/
void sync(long txid) throws IOException;
/**
* @param forceSync Flag to force sync rather than flushing to the buffer. Example - Hadoop hflush
* vs hsync.
*/
default void sync(boolean forceSync) throws IOException {
sync();
}
/**
* @param txid Transaction id to sync to.
* @param forceSync Flag to force sync rather than flushing to the buffer. Example - Hadoop hflush
* vs hsync.
*/
default void sync(long txid, boolean forceSync) throws IOException {
sync(txid);
}
/**
* WAL keeps track of the sequence numbers that are as yet not flushed im memstores in order to be
* able to do accounting to figure which WALs can be let go. This method tells WAL that some
* region is about to flush. The flush can be the whole region or for a column family of the
* region only.
*
* Currently, it is expected that the update lock is held for the region; i.e. no concurrent
* appends while we set up cache flush.
* @param families Families to flush. May be a subset of all families in the region.
* @return Returns {@link HConstants#NO_SEQNUM} if we are flushing the whole region OR if we are
* flushing a subset of all families but there are no edits in those families not being
* flushed; in other words, this is effectively same as a flush of all of the region
* though we were passed a subset of regions. Otherwise, it returns the sequence id of the
* oldest/lowest outstanding edit.
* @see #completeCacheFlush(byte[], long)
* @see #abortCacheFlush(byte[])
*/
Long startCacheFlush(final byte[] encodedRegionName, Set families);
Long startCacheFlush(final byte[] encodedRegionName, Map familyToSeq);
/**
* Complete the cache flush.
* @param encodedRegionName Encoded region name.
* @param maxFlushedSeqId The maxFlushedSeqId for this flush. There is no edit in memory that is
* less that this sequence id.
* @see #startCacheFlush(byte[], Set)
* @see #abortCacheFlush(byte[])
*/
void completeCacheFlush(final byte[] encodedRegionName, long maxFlushedSeqId);
/**
* Abort a cache flush. Call if the flush fails. Note that the only recovery for an aborted flush
* currently is a restart of the regionserver so the snapshot content dropped by the failure gets
* restored to the memstore.
* @param encodedRegionName Encoded region name.
*/
void abortCacheFlush(byte[] encodedRegionName);
/** Returns Coprocessor host. */
WALCoprocessorHost getCoprocessorHost();
/**
* Gets the earliest unflushed sequence id in the memstore for the region.
* @param encodedRegionName The region to get the number for.
* @return The earliest/lowest/oldest sequence id if present, HConstants.NO_SEQNUM if absent.
* @deprecated Since version 1.2.0. Removing because not used and exposes subtle internal
* workings. Use {@link #getEarliestMemStoreSeqNum(byte[], byte[])}
*/
@Deprecated
long getEarliestMemStoreSeqNum(byte[] encodedRegionName);
/**
* Gets the earliest unflushed sequence id in the memstore for the store.
* @param encodedRegionName The region to get the number for.
* @param familyName The family to get the number for.
* @return The earliest/lowest/oldest sequence id if present, HConstants.NO_SEQNUM if absent.
*/
long getEarliestMemStoreSeqNum(byte[] encodedRegionName, byte[] familyName);
/**
* Human readable identifying information about the state of this WAL. Implementors are encouraged
* to include information appropriate for debugging. Consumers are advised not to rely on the
* details of the returned String; it does not have a defined structure.
*/
@Override
String toString();
/**
* When outside clients need to consume persisted WALs, they rely on a provided Reader.
*/
interface Reader extends Closeable {
Entry next() throws IOException;
Entry next(Entry reuse) throws IOException;
void seek(long pos) throws IOException;
long getPosition() throws IOException;
void reset() throws IOException;
}
/**
* Utility class that lets us keep track of the edit with it's key.
*/
class Entry {
private final WALEdit edit;
private final WALKeyImpl key;
public Entry() {
this(new WALKeyImpl(), new WALEdit());
}
/**
* Constructor for both params
* @param edit log's edit
* @param key log's key
*/
public Entry(WALKeyImpl key, WALEdit edit) {
this.key = key;
this.edit = edit;
}
/**
* Gets the edit
*/
public WALEdit getEdit() {
return edit;
}
/**
* Gets the key
*/
public WALKeyImpl getKey() {
return key;
}
/**
* Set compression context for this entry. Compression context
* @deprecated deparcated since hbase 2.1.0
*/
@Deprecated
public void setCompressionContext(CompressionContext compressionContext) {
key.setCompressionContext(compressionContext);
}
@Override
public String toString() {
return this.key + "=" + this.edit;
}
}
/**
* Split a WAL filename to get a start time. WALs usually have the time we start writing to them
* as part of their name, usually the suffix. Sometimes there will be an extra suffix as when it
* is a WAL for the meta table. For example, WALs might look like this
* 10.20.20.171%3A60020.1277499063250 where 1277499063250 is the
* timestamp. Could also be a meta WAL which adds a '.meta' suffix or a synchronous replication
* WAL which adds a '.syncrep' suffix. Check for these. File also may have no timestamp on it. For
* example the recovered.edits files are WALs but are named in ascending order. Here is an
* example: 0000000000000016310. Allow for this.
* @param name Name of the WAL file.
* @return Timestamp or -1.
*/
public static long getTimestamp(String name) {
String[] splits = name.split("\\.");
if (splits.length <= 1) {
return -1;
}
String timestamp = splits[splits.length - 1];
if (!isNumeric(timestamp)) {
// Its a '.meta' or a '.syncrep' suffix.
timestamp = splits[splits.length - 2];
if (!isNumeric(timestamp)) {
return -1;
}
}
return Long.parseLong(timestamp);
}
}