public synchronized void expireServer(final HServerInfo hsi) {
// 首先从onlineServers中获取HServerInfo
// <hostname> , <port> , <startcode>
String serverName = hsi.getServerName();
HServerInfo info = this.onlineServers .get(serverName);
//假如info为空，则抛出server不在线的警告并且返回
if (info == null) {
LOG.warn( "Received expiration of " + hsi.getServerName() +
" but server is not currently online" );
return;
}
//这个作者都怀疑是否会发生这样的情况了，我也想不出什么情况下会发生满足一下if条件的情景
if (this. deadservers.contains(serverName)) {
// TODO : Can this happen? It shouldn't be online in this case?
LOG.warn( "Received expiration of " + hsi.getServerName() +
" but server shutdown is already in progress" );
return;
}
// 已挂列表中add，在线列表中remove
this. deadservers.add(serverName);
this. onlineServers.remove(serverName);
this. serverConnections.remove(serverName);
//如果集群正在关闭，则不处理， 直接return了
if (this. clusterShutdown) {
LOG.info( "Cluster shutdown set; " + hsi.getServerName() +
" expired; onlineServers=" + this .onlineServers .size());
if (this. onlineServers.isEmpty()) {
master.stop( "Cluster shutdown set; onlineServer=0" );
}
return;
}
//通过CatalogTracker判断挂掉的rs中是否还有root和meta，注意CatalogTracker是只读的
CatalogTracker ct = this.master .getCatalogTracker();
// Was this server carrying root?
boolean carryingRoot;
try {
HServerAddress address = ct.getRootLocation();
//看看挂掉的rs是否带有root信息
carryingRoot = address != null && hsi.getServerAddress().equals(address);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
LOG.info( "Interrupted");
return;
}
HServerAddress address = ct.getMetaLocation();
//看看挂掉的rs中是否带有meta信息
boolean carryingMeta = address != null && hsi.getServerAddress().equals(address);
// MetaServerShutdownHandler是继承ServerShutdownHandler, 前者在恢复时需要assign root或者 assign meta
if (carryingRoot || carryingMeta) {
this. services. getExecutorService().submit(new MetaServerShutdownHandler(this .master ,
this.services , this.deadservers, info, carryingRoot, carryingMeta));
} else {
this. services. getExecutorService().submit(new ServerShutdownHandler(this .master ,
this.services , this.deadservers, info));
}
LOG.debug( "Added=" + serverName +
" to dead servers, submitted shutdown handler to be executed, root=" +
carryingRoot + ", meta=" + carryingMeta);
}
接下来走到ServerShutdownHandler， 继承于 EventHandler, 最终走到process方法
public void process() throws IOException {
final String serverName = this.hsi .getServerName();
LOG.info( "Splitting logs for " + serverName);
try {
// split log， split出的log跟着region走 split log在每个版本中的做法相差很大，92中就引入了分布式处理的方式， 看下几段的代码
this. services.getMasterFileSystem().splitLog(serverName);
// 这部分说到底就是返回rsi，当然里面涉及到了regionPlans,deadRegions之类的东西，都是与传进去的参数hsi有关的
List<RegionState> regionsInTransition =
this.services .getAssignmentManager().processServerShutdown(this. hsi);
// 假如有root需要恢复，那就先分配root，分配之前还需要检查一下root的location是不是已经确定
if (isCarryingRoot()) { // -ROOT-
LOG.info("Server " + serverName + " was carrying ROOT. Trying to assign.");
verifyAndAssignRootWithRetries();
}
// 假如有meta需要恢复，那就先分配meta，随机分配rs
if (isCarryingMeta()) {
LOG.info("Server " + serverName + " was carrying META. Trying to assign.");
this.services .getAssignmentManager().assignMeta();
}
// 需要等到所有持有meta的region都open好以后才能进行下面的工作
NavigableMap<HRegionInfo, Result> hris = null;
while (! this.server .isStopped()) {
try {
this.server .getCatalogTracker().waitForMeta();
hris = MetaReader. getServerUserRegions(this. server.getCatalogTracker(),
this.hsi );
break;
} catch (InterruptedException e) {
Thread. currentThread().interrupt();
throw new IOException("Interrupted", e);
} catch (IOException ioe) {
LOG.info("Received exception accessing META during server shutdown of " +
serverName + ", retrying META read", ioe);
}
}
// Skip regions that were in transition unless CLOSING or PENDING_CLOSE
for (RegionState rit : regionsInTransition) {
if (!rit.isClosing() && !rit.isPendingClose()) {
LOG.debug("Removed " + rit.getRegion().getRegionNameAsString() +
" from list of regions to assign because in RIT" );
hris.remove(rit.getRegion());
}
}
LOG.info( "Reassigning " + (hris == null? 0: hris.size()) +
" region(s) that " + serverName +
" was carrying (skipping " + regionsInTransition.size() +
" regions(s) that are already in transition)" );
// 开始分配region，分配前先检查region所属的表是否正在被disable，或者集群是否正在被关闭
// 接下来将region的状态强制设为offline，最后的assign请参看下面对这个方法的分析
for (Map.Entry<HRegionInfo, Result> e: hris.entrySet()) {
if (processDeadRegion(e.getKey(), e.getValue(),
this.services .getAssignmentManager(),
this.server .getCatalogTracker())) {
this.services .getAssignmentManager().assign(e.getKey(), true);
}
}
} finally {
this. deadServers.finish(serverName);
}
LOG.info( "Finished processing of shutdown of " + serverName);
}
split log的相关代码：
public void splitLog(final String serverName ) {
// 首先获取锁
this. splitLogLock.lock();
long splitTime = 0, splitLogSize = 0;
// 在hdfs中获取该rs的WAL位置 一般在/hbase/.logs文件夹中
Path logDir = new Path( this.rootdir , HLog.getHLogDirectoryName (serverName));
try {
//创建splitter对象负责split工作
HLogSplitter splitter = HLogSplitter. createLogSplitter(
conf, rootdir, logDir, oldLogDir, this .fs );
try {
//假如hdfs处于安全模式，那么阻塞知道文件系统退出安全模式
FSUtils. waitOnSafeMode(conf,
conf.getInt(HConstants. THREAD_WAKE_FREQUENCY, 1000));
//进行split
splitter.splitLog();
} catch (OrphanHLogAfterSplitException e) {
LOG.warn("Retrying splitting because of:" , e);
//发生异常后重新获得实例，再试一遍
splitter = HLogSplitter. createLogSplitter(conf, rootdir, logDir, oldLogDir, this .fs );
splitter.splitLog();
}
//下面两个参数用来统计
splitTime = splitter.getTime();
splitLogSize = splitter.getSize();
} catch (IOException e) {
checkFileSystem();
LOG.error( "Failed splitting " + logDir.toString(), e);
} finally {
this. splitLogLock.unlock();
}
if (this. metrics != null) {
this. metrics.addSplit(splitTime, splitLogSize);
}
}
//这边大多数就做些检查的工作
public List<Path> splitLog() throws IOException {
Preconditions.checkState(!hasSplit ,
"An HLogSplitter instance may only be used once" );
hasSplit = true;
long startTime = System. currentTimeMillis();
List<Path> splits = null;
//检查是否存在存放log的目录，假如不存在的话，直接返回
if (! fs.exists( srcDir)) {
// Nothing to do
return splits;
}
FileStatus[] logfiles = fs.listStatus( srcDir);
//检查目录下的文件是否有问题
if (logfiles == null || logfiles.length == 0) {
// Nothing to do
return splits;
}
LOG.info( "Splitting " + logfiles.length + " hlog(s) in "
+ srcDir.toString());
//执行split动作
splits = splitLog(logfiles);
splitTime = System. currentTimeMillis() - startTime;
LOG.info( "hlog file splitting completed in " + splitTime + " ms for " + srcDir .toString());
return splits;
}
private List<Path> splitLog(final FileStatus[] logfiles) throws IOException {
//以下两个列表分别维护了已经处理成功的log及已经损坏的log
List<Path> processedLogs = new ArrayList<Path>();
List<Path> corruptedLogs = new ArrayList<Path>();
List<Path> splits = null;
//这里是配置遇到错误怎样处理，默认为true，会把那些读的时候出问题的log转到.corrupt目录下
//假如设为false，那么只要在split过程中出现问题，就直接抛出IOException, 整个split过程立即终止
boolean skipErrors = conf.getBoolean( "hbase.hlog.split.skip.errors" , true);
splitSize = 0;
//启动写线程
outputSink.startWriterThreads( entryBuffers);
try {
int i = 0;
//遍历需要处理的文件
for (FileStatus log : logfiles) {
Path logPath = log.getPath();
long logLength = log.getLen();
splitSize += logLength;
LOG.debug("Splitting hlog " + (i++ + 1) + " of " + logfiles. length
+ ": " + logPath + ", length=" + logLength);
try {
recoverFileLease(fs, logPath, conf);
//解析Log，将其放进entryBuffer，里面涉及到了HLogKey,它里面存储了region名和表名
//还有一个Entry类，它封装了WALEDIT和HLogKey, 到最后就放到了一个map结构中
//key和value分别为一些列的region及相应的edits
parseHLog(log, entryBuffers, fs , conf );
//将处理完的收集起来
processedLogs.add(logPath);
} catch (EOFException eof) {
// truncated files are expected if a RS crashes (see HBASE-2643)
LOG.info("EOF from hlog " + logPath + ". Continuing");
processedLogs.add(logPath);
} catch (FileNotFoundException fnfe) {
// A file may be missing if the region server was able to archive it
// before shutting down. This means the edits were persisted already
LOG.info("A log was missing " + logPath +
", probably because it was moved by the" +
" now dead region server. Continuing" );
processedLogs.add(logPath);
} catch (IOException e) {
// If the IOE resulted from bad file format,
// then this problem is idempotent and retrying won't help
if (e.getCause() instanceof ParseException) {
LOG.warn("Parse exception from hlog " + logPath + ". continuing", e);
processedLogs.add(logPath);
} else {
if (skipErrors) {
LOG.info("Got while parsing hlog " + logPath +
". Marking as corrupted", e);
corruptedLogs.add(logPath);
} else {
throw e;
}
}
}
}
if (fs.listStatus( srcDir). length > processedLogs.size()
+ corruptedLogs.size()) {
throw new OrphanHLogAfterSplitException(
"Discovered orphan hlog after split. Maybe the "
+ "HRegionServer was not dead when we started" );
}
//就做一些移动文件的事情
//归档logfiles，把有损坏及跳过的log放到.corrupt文件中,再把处理好的放到.oldlogs中，最后把./logs下面那个挂掉的rs给删除了
archiveLogs(srcDir , corruptedLogs, processedLogs, oldLogDir, fs, conf);
} finally {
//等待线程执行结束
splits = outputSink.finishWritingAndClose();
}
return splits;
}
分配region的时候：
private void assign(final RegionState state, final boolean setOfflineInZK, final boolean forceNewPlan) {
for ( int i = 0; i < this.maximumAssignmentAttempts; i++) {
if (setOfflineInZK && !setOfflineInZooKeeper(state)) return;
//master挂了，还搞个啥？直接退出
if (this. master.isStopped()) {
LOG.debug("Server stopped; skipping assign of " + state);
return;
}
// 获取RegionPlan，注意到LoadBalancer.randomAssignment(servers)，即把这个region随机分配到server上
RegionPlan plan = getRegionPlan(state, forceNewPlan);
// 假如获取plan失败，那就退出
if (plan == null) {
debugLog(state.getRegion(),
"Unable to determine a plan to assign " + state);
return; // Should get reassigned later when RIT times out.
}
try {
debugLog(state.getRegion(),
"Assigning region " + state.getRegion().getRegionNameAsString() +
" to " + plan.getDestination().getServerName());
// 将region的状态设置为PENDING_OPEN
state.update(RegionState.State. PENDING_OPEN);
// 向rs发送请求，要求其open
serverManager.sendRegionOpen(plan.getDestination(), state.getRegion());
break;
} catch (Throwable t) {
LOG.warn("Failed assignment of " +
state.getRegion().getRegionNameAsString() + " to " +
plan.getDestination() + ", trying to assign elsewhere instead; " +
"retry=" + i, t);
// Clean out plan we failed execute and one that doesn't look like it'll
// succeed anyways; we need a new plan!
// Transition back to OFFLINE
state.update(RegionState.State. OFFLINE);
// Force a new plan and reassign. Will return n
// ull if no servers.
if (getRegionPlan(state, plan.getDestination(), true) == null) {
LOG.warn("Unable to find a viable location to assign region " +
state.getRegion().getRegionNameAsString());
return;
}
}
}
}
最后，regionserver会执行openRegionHandler来打开这个region， 这是一个异步的过程。这里面其实还涉及到了region在zk中的状态变化，包括在打开region之前的HLog恢复，恢复过程和正常的向HBase写数据一样，都会先写到memstore中，最后需要更新meta表。
当然了，如果region带有meta或者root信息，那处理方式也会变得不太一样。
@Override
@QosPriority(priority= HIGH_QOS )
public void openRegion(HRegionInfo region)
throws IOException {
if ( this. regionsInTransitionInRS .contains(region.getEncodedNameAsBytes())) {
throw new RegionAlreadyInTransitionException("open" , region.getEncodedName());
}
LOG.info( "Received request to open region: " +
region.getRegionNameAsString());
if ( this. stopped) throw new RegionServerStoppedException();
this. regionsInTransitionInRS .add(region.getEncodedNameAsBytes());
//会因为region的类型不同而进入不一样的分支
if (region.isRootRegion()) {
this. service.submit( new OpenRootHandler( this, this, region));
} else if (region.isMetaRegion()) {
this. service.submit( new OpenMetaHandler( this, this, region));
} else {
this. service.submit( new OpenRegionHandler( this , this , region));
}
}