hbase的table delete之前需要将该table disable,今天结合源码分析一下disable的过程
首先看客户端HbaseAdmin.java中有接口
public void disableTable(final byte [] tableName)
public void disableTable(final String tableName)
它们的实现都是
public void disableTableAsync(final byte [] tableName) throws IOException {
isMasterRunning();
try {
getMaster().disableTable(tableName);
} catch (RemoteException e) {
throw e.unwrapRemoteException();
}
LOG.info("Started disable of " + Bytes.toString(tableName));
}
这段代码的主要过程是通过rpc远程调用执行HMaster的disableTable();
所以我直接看HMaster的disableTable函数
public void disableTable(final byte [] tableName) throws IOException {
this.executorService.submit(new DisableTableHandler(this, tableName,
catalogTracker, assignmentManager));
}
起了一个新线程DisableTableHadnler
首先判断meta表中是否存在该table,扫描meta表,若meta表不存在table则返回,抛出异常tablenotexist
该线程主要调用
private void handleDisableTable()
将zk上面的/table/tablename标识为DISABLING
this.assignmentManager.getZKTable().setDisablingTable(this.tableNameStr);
boolean done = false;
while (true) {
// Get list of online regions that are of this table. Regions that are
// already closed will not be included in this list; i.e. the returned
// list is not ALL regions in a table, its all online regions according to
// the in-memory state on this master.
final List<HRegionInfo> regions =
this.assignmentManager.getRegionsOfTable(tableName);
if (regions.size() == 0) {
done = true;
break;
}
LOG.info("Offlining " + regions.size() + " regions.");
BulkDisabler bd = new BulkDisabler(this.server, regions);
try {
if (bd.bulkAssign()) {
done = true;
break;
}
} catch (InterruptedException e) {
LOG.warn("Disable was interrupted");
// Preserve the interrupt.
Thread.currentThread().interrupt();
break;
}
}
// Flip the table to disabled if success.
if (done) this.assignmentManager.getZKTable().setDisabledTable(this.tableNameStr);
获取该table上的所有online的region集合。
对于这些regions bulkassign:起20个线程对所有region进行unassigned
protected void populatePool(ExecutorService pool) {
for (HRegionInfo region: regions) {
if (assignmentManager.isRegionInTransition(region) != null) continue;
final HRegionInfo hri = region;
pool.execute(new Runnable() {
public void run() {
assignmentManager.unassign(hri);
}
});
}
}
如上所示如果该Region已经在master的RIT队列中,则说明该region正在被处理,则忽略之
下面我们来看unassigned过程:
1. 该region必须online,在master的online队列中存在
2. 若该region在master的RIT队列中,且其state的状态是PENDING且force=true即表示即使该region正在closing ,force参数指定该region should be closed;
若在RIT中且不符合上面条件则忽略返回;
若不存在则将当前Region加入RIT队列中
3. serverManager.sendRegionClose(server, state.getRegion()),Master端与该Region所在RS进行通信,RPC调用HRegionServer的closeRegion(region)函数
HRegionServer端
closeRegion(region)
1. 该region在RS的online regions列表上
2. 起一个线程CloseRegionhandler实现以下步骤
1)setClosingState,在zk上创建unassigned下的该region节点将其值置为RS_ZK_REGION_CLOSING
2)region.close(abort),关闭region,主要是关闭region下每个Store的每个HFile的reader
3)将region从当前online列表中移除
4)在zk上将该节点置为RS_ZK_REGION_CLOSED
5)从RS的RIT队列中移除该region
Server端的主要逻辑即为如上所示
在上面过程中由于对zk上的unassigned节点进行了created和changed,且master端watch了该节点,当这些节点发生变化时会使得Master端也发生变化。
1)created时
public void nodeCreated(String path) {
if(path.startsWith(watcher.assignmentZNode)) {
synchronized(regionsInTransition) {
try {
RegionTransitionData data = ZKAssign.getData(watcher, path);
if(data == null) {
return;
}
handleRegion(data);
} catch (KeeperException e) {
master.abort("Unexpected ZK exception reading unassigned node data", e);
}
}
}
}
handleRegion的过程是将Master的RIT队列中该region的state置为CLOSING
2)变成Closed时
handleRegion将该region的state置为CLOSED然后力气一个线程CloseRegionHandler,此时如果zk上面/table下存在该table的节点,那么offlineDisabledRegion(HRegionInfo regionInfo)
1.删除zk上的unassigned节点,
2.clear regionplan
3.从Master的online region和server上移除该region
4.RIT中移除
整个过程结束。首先与hmaster进行通信,而后hmaster和rs进行通信,关闭region上各个HStore的Hfile的reader,在这个过程中涉及zk上节点的变化,master亦有相应的改变。