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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* 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 java.io.IOException;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.wal.WALSplitter.PipelineController;
import org.apache.hadoop.hbase.wal.WALSplitter.RegionEntryBuffer;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Class which accumulates edits and separates them into a buffer per region while simultaneously
* accounting RAM usage. Blocks if the RAM usage crosses a predefined threshold. Writer threads then
* pull region-specific buffers from this class.
*/
@InterfaceAudience.Private
public class EntryBuffers {
private static final Logger LOG = LoggerFactory.getLogger(EntryBuffers.class);
PipelineController controller;
Map buffers = new TreeMap<>(Bytes.BYTES_COMPARATOR);
/*
* Track which regions are currently in the middle of writing. We don't allow an IO thread to pick
* up bytes from a region if we're already writing data for that region in a different IO thread.
*/
Set currentlyWriting = new TreeSet<>(Bytes.BYTES_COMPARATOR);
long totalBuffered = 0;
long maxHeapUsage;
boolean splitWriterCreationBounded;
public EntryBuffers(PipelineController controller, long maxHeapUsage) {
this(controller, maxHeapUsage, false);
}
public EntryBuffers(PipelineController controller, long maxHeapUsage,
boolean splitWriterCreationBounded) {
this.controller = controller;
this.maxHeapUsage = maxHeapUsage;
this.splitWriterCreationBounded = splitWriterCreationBounded;
}
/**
* Append a log entry into the corresponding region buffer. Blocks if the total heap usage has
* crossed the specified threshold.
*/
public void appendEntry(WAL.Entry entry) throws InterruptedException, IOException {
WALKey key = entry.getKey();
RegionEntryBuffer buffer;
long incrHeap;
synchronized (this) {
buffer = buffers.get(key.getEncodedRegionName());
if (buffer == null) {
buffer = new RegionEntryBuffer(key.getTableName(), key.getEncodedRegionName());
buffers.put(key.getEncodedRegionName(), buffer);
}
incrHeap = buffer.appendEntry(entry);
}
// If we crossed the chunk threshold, wait for more space to be available
synchronized (controller.dataAvailable) {
totalBuffered += incrHeap;
while (totalBuffered > maxHeapUsage && controller.thrown.get() == null) {
LOG.debug("Used {} bytes of buffered edits, waiting for IO threads", totalBuffered);
controller.dataAvailable.wait(2000);
}
controller.dataAvailable.notifyAll();
}
controller.checkForErrors();
}
/**
* @return RegionEntryBuffer a buffer of edits to be written.
*/
synchronized RegionEntryBuffer getChunkToWrite() {
// The core part of limiting opening writers is it doesn't return chunk only if the
// heap size is over maxHeapUsage. Thus it doesn't need to create a writer for each
// region during splitting. It will flush all the logs in the buffer after splitting
// through a threadpool, which means the number of writers it created is under control.
if (splitWriterCreationBounded && totalBuffered < maxHeapUsage) {
return null;
}
long biggestSize = 0;
byte[] biggestBufferKey = null;
for (Map.Entry entry : buffers.entrySet()) {
long size = entry.getValue().heapSize();
if (size > biggestSize && (!currentlyWriting.contains(entry.getKey()))) {
biggestSize = size;
biggestBufferKey = entry.getKey();
}
}
if (biggestBufferKey == null) {
return null;
}
RegionEntryBuffer buffer = buffers.remove(biggestBufferKey);
currentlyWriting.add(biggestBufferKey);
return buffer;
}
void doneWriting(RegionEntryBuffer buffer) {
synchronized (this) {
boolean removed = currentlyWriting.remove(buffer.encodedRegionName);
assert removed;
}
long size = buffer.heapSize();
synchronized (controller.dataAvailable) {
totalBuffered -= size;
// We may unblock writers
controller.dataAvailable.notifyAll();
}
}
synchronized boolean isRegionCurrentlyWriting(byte[] region) {
return currentlyWriting.contains(region);
}
public void waitUntilDrained() {
synchronized (controller.dataAvailable) {
while (totalBuffered > 0) {
try {
controller.dataAvailable.wait(2000);
} catch (InterruptedException e) {
LOG.warn("Got interrupted while waiting for EntryBuffers is drained");
Thread.interrupted();
break;
}
}
}
}
}