Possiblilty of RS opening a region though tickleOpening fails due to znode
version mismatch
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Key: HBASE-4452
URL: https://issues.apache.org/jira/browse/HBASE-4452
Project: HBase
Issue Type: Bug
Reporter: ramkrishna.s.vasudevan
Assignee: ramkrishna.s.vasudevan
Priority: Critical
Consider the following code
{code}
long period = Math.max(1, assignmentTimeout/ 3);
long lastUpdate = now;
while (!signaller.get() && t.isAlive() && !this.server.isStopped() &&
!this.rsServices.isStopping() && (endTime > now)) {
long elapsed = now - lastUpdate;
if (elapsed > period) {
// Only tickle OPENING if postOpenDeployTasks is taking some time.
lastUpdate = now;
tickleOpening("post_open_deploy");
}
{code}
Whenever the postopenDeploy tasks takes considerable time we try to
tickleOpening so that there is no timeout deducted. But before it could do
this if the TimeoutMonitor tries to assign the node to another RS then the
other RS will move the node from OFFLINE to OPENING. Hence when the first RS
tries to do tickleOpening the operation will fail. Now here lies the problem,
{code}
String encodedName = this.regionInfo.getEncodedName();
try {
this.version =
ZKAssign.retransitionNodeOpening(server.getZooKeeper(),
this.regionInfo, this.server.getServerName(), this.version);
} catch (KeeperException e) {
{code}
Now this.version becomes -1 as the operation failed.
Now as in the first code snippet as the return type is not captured after
tickleOpening() failes we go on with moving the node to OPENED. Here again we
dont have any check for this condition as already the version has been changed
to -1. Hence the OPENING to OPENED becomes successful. Chances of double
assignment.
{noformat}
2011-09-22 00:57:29,930 WARN org.apache.hadoop.hbase.zookeeper.ZKAssign:
regionserver:60020-0x1328ceaa1ff000d Attempt to transition the unassigned node
for 69797d064f773d1aa9adba56e7ff90a3 from RS_ZK_REGION_OPENING to
RS_ZK_REGION_OPENING failed, the node existed but was version 5 not the
expected version 2
2011-09-22 00:57:33,494 WARN
org.apache.hadoop.hbase.regionserver.handler.OpenRegionHandler: Failed
refreshing OPENING; region=69797d064f773d1aa9adba56e7ff90a3,
context=post_open_deploy
2011-09-22 00:58:02,356 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
regionserver:60020-0x1328ceaa1ff000d Attempting to transition node
69797d064f773d1aa9adba56e7ff90a3 from RS_ZK_REGION_OPENING to
RS_ZK_REGION_OPENED
2011-09-22 00:58:11,853 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
regionserver:60020-0x1328ceaa1ff000d Successfully transitioned node
69797d064f773d1aa9adba56e7ff90a3 from RS_ZK_REGION_OPENING to
RS_ZK_REGION_OPENED
2011-09-22 00:58:13,956 DEBUG
org.apache.hadoop.hbase.regionserver.handler.OpenRegionHandler: Opened
t9,,1316633193606.69797d064f773d1aa9adba56e7ff90a3.
{noformat}
Correct me if this analysis is wrong.
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