/**
*
* 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.regionserver;
import java.io.IOException;
import java.lang.Thread.UncaughtExceptionHandler;
import java.lang.management.ManagementFactory;
import java.util.ArrayList;
import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.DroppedSnapshotException;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.RemoteExceptionHandler;
import org.apache.hadoop.hbase.io.util.HeapMemorySizeUtil;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
import org.apache.hadoop.hbase.util.HasThread;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.hadoop.util.StringUtils;
import org.apache.htrace.Trace;
import org.apache.htrace.TraceScope;
import org.apache.hadoop.hbase.util.Counter;
import com.google.common.base.Preconditions;
/**
* Thread that flushes cache on request
*
* NOTE: This class extends Thread rather than Chore because the sleep time
* can be interrupted when there is something to do, rather than the Chore
* sleep time which is invariant.
*
* @see FlushRequester
*/
@InterfaceAudience.Private
class MemStoreFlusher implements FlushRequester {
static final Log LOG = LogFactory.getLog(MemStoreFlusher.class);
// These two data members go together. Any entry in the one must have
// a corresponding entry in the other.
private final BlockingQueue<FlushQueueEntry> flushQueue =
new DelayQueue<FlushQueueEntry>();
private final Map<HRegion, FlushRegionEntry> regionsInQueue =
new HashMap<HRegion, FlushRegionEntry>();
private AtomicBoolean wakeupPending = new AtomicBoolean();
private final long threadWakeFrequency;
private final HRegionServer server;
//自定义的某种锁，待研究
private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
private final Object blockSignal = new Object();
protected long globalMemStoreLimit;
protected float globalMemStoreLimitLowMarkPercent;
protected long globalMemStoreLimitLowMark;
private long blockingWaitTime;
private final Counter updatesBlockedMsHighWater = new Counter();
private final FlushHandler[] flushHandlers;
private List<FlushRequestListener> flushRequestListeners = new ArrayList<FlushRequestListener>(1);
/**
* @param conf
* @param server
*/
public MemStoreFlusher(final Configuration conf,
final HRegionServer server) {
super();
this.server = server;
this.threadWakeFrequency =
conf.getLong(HConstants.THREAD_WAKE_FREQUENCY, 10 * 1000);
long max = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage().getMax();
float globalMemStorePercent = HeapMemorySizeUtil.getGlobalMemStorePercent(conf, true);
this.globalMemStoreLimit = (long) (max * globalMemStorePercent);
this.globalMemStoreLimitLowMarkPercent =
HeapMemorySizeUtil.getGlobalMemStoreLowerMark(conf, globalMemStorePercent);
this.globalMemStoreLimitLowMark =
(long) (this.globalMemStoreLimit * this.globalMemStoreLimitLowMarkPercent);
this.blockingWaitTime = conf.getInt("hbase.hstore.blockingWaitTime",
90000);
int handlerCount = conf.getInt("hbase.hstore.flusher.count", 2);
this.flushHandlers = new FlushHandler[handlerCount];
LOG.info("globalMemStoreLimit=" +
StringUtils.humanReadableInt(this.globalMemStoreLimit) +
", globalMemStoreLimitLowMark=" +
StringUtils.humanReadableInt(this.globalMemStoreLimitLowMark) +
", maxHeap=" + StringUtils.humanReadableInt(max));
}
public Counter getUpdatesBlockedMsHighWater() {
return this.updatesBlockedMsHighWater;
}
/**
* The memstore across all regions has exceeded the low water mark. Pick
* one region to flush and flush it synchronously (this is called from the
* flush thread)
* @return true if successful
*/
private boolean flushOneForGlobalPressure() {
SortedMap<Long, HRegion> regionsBySize =
server.getCopyOfOnlineRegionsSortedBySize();
Set<HRegion> excludedRegions = new HashSet<HRegion>();
boolean flushedOne = false;
while (!flushedOne) {
// Find the biggest region that doesn't have too many storefiles
// (might be null!)
HRegion bestFlushableRegion = getBiggestMemstoreRegion(
regionsBySize, excludedRegions, true);
// Find the biggest region, total, even if it might have too many flushes.
HRegion bestAnyRegion = getBiggestMemstoreRegion(
regionsBySize, excludedRegions, false);
if (bestAnyRegion == null) {
LOG.error("Above memory mark but there are no flushable regions!");
return false;
}
HRegion regionToFlush;
if (bestFlushableRegion != null &&
bestAnyRegion.memstoreSize.get() > 2 * bestFlushableRegion.memstoreSize.get()) {
// Even if it's not supposed to be flushed, pick a region if it's more than twice
// as big as the best flushable one - otherwise when we're under pressure we make
// lots of little flushes and cause lots of compactions, etc, which just makes
// life worse!
if (LOG.isDebugEnabled()) {
LOG.debug("Under global heap pressure: " +
"Region " + bestAnyRegion.getRegionNameAsString() + " has too many " +
"store files, but is " +
StringUtils.humanReadableInt(bestAnyRegion.memstoreSize.get()) +
" vs best flushable region's " +
StringUtils.humanReadableInt(bestFlushableRegion.memstoreSize.get()) +
". Choosing the bigger.");
}
regionToFlush = bestAnyRegion;
} else {
if (bestFlushableRegion == null) {
regionToFlush = bestAnyRegion;
} else {
regionToFlush = bestFlushableRegion;
}
}
Preconditions.checkState(regionToFlush.memstoreSize.get() > 0);
LOG.info("Flush of region " + regionToFlush + " due to global heap pressure");
flushedOne = flushRegion(regionToFlush, true);
if (!flushedOne) {
LOG.info("Excluding unflushable region " + regionToFlush +
" - trying to find a different region to flush.");
excludedRegions.add(regionToFlush);
}
}
return true;
}
private class FlushHandler extends HasThread {
private FlushHandler(String name) {
super(name);
}
@Override
public void run() {
while (!server.isStopped()) {
FlushQueueEntry fqe = null;
try {
wakeupPending.set(false); // allow someone to wake us up again
fqe = flushQueue.poll(threadWakeFrequency, TimeUnit.MILLISECONDS);
if (fqe == null || fqe instanceof WakeupFlushThread) {
if (isAboveLowWaterMark()) {
LOG.debug("Flush thread woke up because memory above low water="
+ StringUtils.humanReadableInt(globalMemStoreLimitLowMark));
if (!flushOneForGlobalPressure()) {
// Wasn't able to flush any region, but we're above low water mark
// This is unlikely to happen, but might happen when closing the
// entire server - another thread is flushing regions. We'll just
// sleep a little bit to avoid spinning, and then pretend that
// we flushed one, so anyone blocked will check again
Thread.sleep(1000);
wakeUpIfBlocking();
}
// Enqueue another one of these tokens so we'll wake up again
wakeupFlushThread();
}
continue;
}
FlushRegionEntry fre = (FlushRegionEntry) fqe;
if (!flushRegion(fre)) {
break;
}
} catch (InterruptedException ex) {
continue;
} catch (ConcurrentModificationException ex) {
continue;
} catch (Exception ex) {
LOG.error("Cache flusher failed for entry " + fqe, ex);
if (!server.checkFileSystem()) {
break;
}
}
}
synchronized (regionsInQueue) {
regionsInQueue.clear();
flushQueue.clear();
}
// Signal anyone waiting, so they see the close flag
wakeUpIfBlocking();
LOG.info(getName() + " exiting");
}
}
private void wakeupFlushThread() {
if (wakeupPending.compareAndSet(false, true)) {
flushQueue.add(new WakeupFlushThread());
}
}
private HRegion getBiggestMemstoreRegion(
SortedMap<Long, HRegion> regionsBySize,
Set<HRegion> excludedRegions,
boolean checkStoreFileCount) {
synchronized (regionsInQueue) {
for (HRegion region : regionsBySize.values()) {
if (excludedRegions.contains(region)) {
continue;
}
if (region.writestate.flushing || !region.writestate.writesEnabled) {
continue;
}
if (checkStoreFileCount && isTooManyStoreFiles(region)) {
continue;
}
return region;
}
}
return null;
}
/**
* Return true if global memory usage is above the high watermark
*/
private boolean isAboveHighWaterMark() {
return server.getRegionServerAccounting().
getGlobalMemstoreSize() >= globalMemStoreLimit;
}
/**
* Return true if we're above the high watermark
*/
private boolean isAboveLowWaterMark() {
return server.getRegionServerAccounting().
getGlobalMemstoreSize() >= globalMemStoreLimitLowMark;
}
public void requestFlush(HRegion r) {
synchronized (regionsInQueue) {
if (!regionsInQueue.containsKey(r)) {
// This entry has no delay so it will be added at the top of the flush
// queue. It'll come out near immediately.
FlushRegionEntry fqe = new FlushRegionEntry(r);
this.regionsInQueue.put(r, fqe);
this.flushQueue.add(fqe);
}
}
}
public void requestDelayedFlush(HRegion r, long delay) {
synchronized (regionsInQueue) {
if (!regionsInQueue.containsKey(r)) {
// This entry has some delay
FlushRegionEntry fqe = new FlushRegionEntry(r);
fqe.requeue(delay);
this.regionsInQueue.put(r, fqe);
this.flushQueue.add(fqe);
}
}
}
public int getFlushQueueSize() {
return flushQueue.size();
}
/**
* Only interrupt once it's done with a run through the work loop.
*/
void interruptIfNecessary() {
lock.writeLock().lock();
try {
for (FlushHandler flushHander : flushHandlers) {
if (flushHander != null) flushHander.interrupt();
}
} finally {
lock.writeLock().unlock();
}
}
synchronized void start(UncaughtExceptionHandler eh) {
ThreadFactory flusherThreadFactory = Threads.newDaemonThreadFactory(
server.getServerName().toShortString() + "-MemStoreFlusher", eh);
for (int i = 0; i < flushHandlers.length; i++) {
flushHandlers[i] = new FlushHandler("MemStoreFlusher." + i);
flusherThreadFactory.newThread(flushHandlers[i]);
flushHandlers[i].start();
}
}
boolean isAlive() {
for (FlushHandler flushHander : flushHandlers) {
if (flushHander != null && flushHander.isAlive()) {
return true;
}
}
return false;
}
void join() {
for (FlushHandler flushHander : flushHandlers) {
if (flushHander != null) {
Threads.shutdown(flushHander.getThread());
}
}
}
/*
* A flushRegion that checks store file count. If too many, puts the flush
* on delay queue to retry later.
* @param fqe
* @return true if the region was successfully flushed, false otherwise. If
* false, there will be accompanying log messages explaining why the log was
* not flushed.
*/
private boolean flushRegion(final FlushRegionEntry fqe) {
HRegion region = fqe.region;
if (!region.getRegionInfo().isMetaRegion() &&
isTooManyStoreFiles(region)) {
if (fqe.isMaximumWait(this.blockingWaitTime)) {
LOG.info("Waited " + (EnvironmentEdgeManager.currentTime() - fqe.createTime) +
"ms on a compaction to clean up 'too many store files'; waited " +
"long enough... proceeding with flush of " +
region.getRegionNameAsString());
} else {
// If this is first time we've been put off, then emit a log message.
if (fqe.getRequeueCount() <= 0) {
// Note: We don't impose blockingStoreFiles constraint on meta regions
LOG.warn("Region " + region.getRegionNameAsString() + " has too many " +
"store files; delaying flush up to " + this.blockingWaitTime + "ms");
if (!this.server.compactSplitThread.requestSplit(region)) {
try {
//当region含有过多的storefile的时候 flush之前需要先进行Region的store file的合并
this.server.compactSplitThread.requestSystemCompaction(
region, Thread.currentThread().getName());
} catch (IOException e) {
LOG.error(
"Cache flush failed for region " + Bytes.toStringBinary(region.getRegionName()),
RemoteExceptionHandler.checkIOException(e));
}
}
}
// Put back on the queue. Have it come back out of the queue
// after a delay of this.blockingWaitTime / 100 ms.
this.flushQueue.add(fqe.requeue(this.blockingWaitTime / 100));
// Tell a lie, it's not flushed but it's ok
return true;
}
}
return flushRegion(region, false);
}
/*
* Flush a region.
* @param region Region to flush.
* @param emergencyFlush Set if we are being force flushed. If true the region
* needs to be removed from the flush queue. If false, when we were called
* from the main flusher run loop and we got the entry to flush by calling
* poll on the flush queue (which removed it).
*
* @return true if the region was successfully flushed, false otherwise. If
* false, there will be accompanying log messages explaining why the log was
* not flushed.
*/
private boolean flushRegion(final HRegion region, final boolean emergencyFlush) {
long startTime = 0;
synchronized (this.regionsInQueue) {
FlushRegionEntry fqe = this.regionsInQueue.remove(region);
// Use the start time of the FlushRegionEntry if available
if (fqe != null) {
startTime = fqe.createTime;
}
if (fqe != null && emergencyFlush) {
// Need to remove from region from delay queue. When NOT an
// emergencyFlush, then item was removed via a flushQueue.poll.
flushQueue.remove(fqe);
}
}
if (startTime == 0) {
// Avoid getting the system time unless we don't have a FlushRegionEntry;
// shame we can't capture the time also spent in the above synchronized
// block
startTime = EnvironmentEdgeManager.currentTime();
}
lock.readLock().lock();
try {
notifyFlushRequest(region, emergencyFlush);//只是对flush线程进行统计
HRegion.FlushResult flushResult = region.flushcache();
boolean shouldCompact = flushResult.isCompactionNeeded();
// We just want to check the size
boolean shouldSplit = region.checkSplit() != null;
if (shouldSplit) {
this.server.compactSplitThread.requestSplit(region);
} else if (shouldCompact) {
server.compactSplitThread.requestSystemCompaction(
region, Thread.currentThread().getName());
}
if (flushResult.isFlushSucceeded()) {
long endTime = EnvironmentEdgeManager.currentTime();
server.metricsRegionServer.updateFlushTime(endTime - startTime);
}
} catch (DroppedSnapshotException ex) {
// Cache flush can fail in a few places. If it fails in a critical
// section, we get a DroppedSnapshotException and a replay of wal
// is required. Currently the only way to do this is a restart of
// the server. Abort because hdfs is probably bad (HBASE-644 is a case
// where hdfs was bad but passed the hdfs check).
server.abort("Replay of WAL required. Forcing server shutdown", ex);
return false;
} catch (IOException ex) {
LOG.error("Cache flush failed" +
(region != null ? (" for region " + Bytes.toStringBinary(region.getRegionName())) : ""),
RemoteExceptionHandler.checkIOException(ex));
if (!server.checkFileSystem()) {
return false;
}
} finally {
lock.readLock().unlock();
wakeUpIfBlocking();
}
return true;
}
private void notifyFlushRequest(HRegion region, boolean emergencyFlush) {
FlushType type = FlushType.NORMAL;
if (emergencyFlush) {
type = isAboveHighWaterMark() ? FlushType.ABOVE_HIGHER_MARK : FlushType.ABOVE_LOWER_MARK;
}
for (FlushRequestListener listener : flushRequestListeners) {
listener.flushRequested(type, region);
}
}
private void wakeUpIfBlocking() {
synchronized (blockSignal) {
blockSignal.notifyAll();
}
}
private boolean isTooManyStoreFiles(HRegion region) {
for (Store store : region.stores.values()) {
if (store.hasTooManyStoreFiles()) {
return true;
}
}
return false;
}
/**
* Check if the regionserver's memstore memory usage is greater than the
* limit. If so, flush regions with the biggest memstores until we're down
* to the lower limit. This method blocks callers until we're down to a safe
* amount of memstore consumption.
*/
public void reclaimMemStoreMemory() {
TraceScope scope = Trace.startSpan("MemStoreFluser.reclaimMemStoreMemory");
if (isAboveHighWaterMark()) {
if (Trace.isTracing()) {
scope.getSpan().addTimelineAnnotation("Force Flush. We're above high water mark.");
}
long start = EnvironmentEdgeManager.currentTime();
synchronized (this.blockSignal) {
boolean blocked = false;
long startTime = 0;
boolean interrupted = false;
try {
while (isAboveHighWaterMark() && !server.isStopped()) {
if (!blocked) {
startTime = EnvironmentEdgeManager.currentTime();
LOG.info("Blocking updates on " + server.toString() +
": the global memstore size " +
StringUtils.humanReadableInt(server.getRegionServerAccounting().getGlobalMemstoreSize()) +
" is >= than blocking " +
StringUtils.humanReadableInt(globalMemStoreLimit) + " size");
}
blocked = true;
wakeupFlushThread();
try {
// we should be able to wait forever, but we've seen a bug where
// we miss a notify, so put a 5 second bound on it at least.
blockSignal.wait(5 * 1000);
} catch (InterruptedException ie) {
LOG.warn("Interrupted while waiting");
interrupted = true;
}
long took = EnvironmentEdgeManager.currentTime() - start;
LOG.warn("Memstore is above high water mark and block " + took + "ms");
}
} finally {
if (interrupted) {
Thread.currentThread().interrupt();
}
}
if(blocked){
final long totalTime = EnvironmentEdgeManager.currentTime() - startTime;
if(totalTime > 0){
this.updatesBlockedMsHighWater.add(totalTime);
}
LOG.info("Unblocking updates for server " + server.toString());
}
}
} else if (isAboveLowWaterMark()) {
wakeupFlushThread();
}
scope.close();
}
@Override
public String toString() {
return "flush_queue="
+ flushQueue.size();
}
public String dumpQueue() {
StringBuilder queueList = new StringBuilder();
queueList.append("Flush Queue Queue dump:\n");
queueList.append(" Flush Queue:\n");
java.util.Iterator<FlushQueueEntry> it = flushQueue.iterator();
while(it.hasNext()){
queueList.append(" "+it.next().toString());
queueList.append("\n");
}
return queueList.toString();
}
/**
* Register a MemstoreFlushListener
* @param listener
*/
public void registerFlushRequestListener(final FlushRequestListener listener) {
this.flushRequestListeners.add(listener);
}
/**
* Unregister the listener from MemstoreFlushListeners
* @param listener
* @return true when passed listener is unregistered successfully.
*/
public boolean unregisterFlushRequestListener(final FlushRequestListener listener) {
return this.flushRequestListeners.remove(listener);
}
/**
* Sets the global memstore limit to a new size.
* @param globalMemStoreSize
*/
public void setGlobalMemstoreLimit(long globalMemStoreSize) {
this.globalMemStoreLimit = globalMemStoreSize;
this.globalMemStoreLimitLowMark =
(long) (this.globalMemStoreLimitLowMarkPercent * globalMemStoreSize);
reclaimMemStoreMemory();
}
public long getMemoryLimit() {
return this.globalMemStoreLimit;
}
interface FlushQueueEntry extends Delayed {
}
/**
* Token to insert into the flush queue that ensures that the flusher does not sleep
*/
static class WakeupFlushThread implements FlushQueueEntry {
@Override
public long getDelay(TimeUnit unit) {
return 0;
}
@Override
public int compareTo(Delayed o) {
return -1;
}
@Override
public boolean equals(Object obj) {
return (this == obj);
}
}
/**
* Datastructure used in the flush queue. Holds region and retry count.
* Keeps tabs on how old this object is. Implements {@link Delayed}. On
* construction, the delay is zero. When added to a delay queue, we'll come
* out near immediately. Call {@link #requeue(long)} passing delay in
* milliseconds before readding to delay queue if you want it to stay there
* a while.
*/
static class FlushRegionEntry implements FlushQueueEntry {
private final HRegion region;
private final long createTime;
private long whenToExpire;
private int requeueCount = 0;
FlushRegionEntry(final HRegion r) {
this.region = r;
this.createTime = EnvironmentEdgeManager.currentTime();
this.whenToExpire = this.createTime;
}
/**
* @param maximumWait
* @return True if we have been delayed > <code>maximumWait</code> milliseconds.
*/
public boolean isMaximumWait(final long maximumWait) {
return (EnvironmentEdgeManager.currentTime() - this.createTime) > maximumWait;
}
/**
* @return Count of times {@link #requeue(long)} was called; i.e this is
* number of times we've been requeued.
*/
public int getRequeueCount() {
return this.requeueCount;
}
/**
* @param when When to expire, when to come up out of the queue.
* Specify in milliseconds. This method adds EnvironmentEdgeManager.currentTime()
* to whatever you pass.
* @return This.
*/
public FlushRegionEntry requeue(final long when) {
this.whenToExpire = EnvironmentEdgeManager.currentTime() + when;
this.requeueCount++;
return this;
}
@Override
public long getDelay(TimeUnit unit) {
return unit.convert(this.whenToExpire - EnvironmentEdgeManager.currentTime(),
TimeUnit.MILLISECONDS);
}
@Override
public int compareTo(Delayed other) {
// Delay is compared first. If there is a tie, compare region's hash code
int ret = Long.valueOf(getDelay(TimeUnit.MILLISECONDS) -
other.getDelay(TimeUnit.MILLISECONDS)).intValue();
if (ret != 0) {
return ret;
}
FlushQueueEntry otherEntry = (FlushQueueEntry) other;
return hashCode() - otherEntry.hashCode();
}
@Override
public String toString() {
return "[flush region " + Bytes.toStringBinary(region.getRegionName()) + "]";
}
@Override
public int hashCode() {
int hash = (int) getDelay(TimeUnit.MILLISECONDS);
return hash ^ region.hashCode();
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || getClass() != obj.getClass()) {
return false;
}
Delayed other = (Delayed) obj;
return compareTo(other) == 0;
}
}
}
enum FlushType {
NORMAL, ABOVE_LOWER_MARK, ABOVE_HIGHER_MARK;
}