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https://issues.apache.org/jira/browse/HBASE-4064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13397332#comment-13397332
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steven zhuang commented on HBASE-4064:
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hi, Ramkrishna, sorry for the late response.
This turn of event came because we wanted to update the hbase jar to enable our
table-balancer without turning the whole cluster off.
Here is what I did:
1. turn off first half RS of the cluster, update the jars
2. turn on the first half RS, (used "hbase-daemon.sh stop " on the RS which
holds the META region coz it won't go down )
3. turn off the second half RS of the cluster, update the jars,
4. turn on the second half RS
At this time, I found the ROOT region is in transition, and status was CLOSING
although the RS hold it was down . So I tried to restart the whole cluster, the
cluster cannot be started now, coz the RS which master believes holds the ROOT
region has no region served, master can only give out
"NotServingRegionException". I closed all the RS, the started the master again,
only to find the master trying to reach the same "ROOT-holding" RS which was
down then, and gave "ServerNotRunningYetException" after dozens of retries.
I guess I restarted the "half cluster" too soon after I closed it, so root
region was still in transition when the original RS restarted, and later I
force closed the whole cluster, but status in ZK cluster stayed. so later when
I restarted the cluster, the master tried to close the ROOT region instead of
start it, but that time, the region is not on any RS, master then fall into a
(dead?) loop.
the log files is all messed up, with splitlog and other crappy exception log,
and is way too big(even just the grepped part) to upload, so hope my
description helps.
> Two concurrent unassigning of the same region caused the endless loop of
> "Region has been PENDING_CLOSE for too long..."
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-4064
> URL: https://issues.apache.org/jira/browse/HBASE-4064
> Project: HBase
> Issue Type: Bug
> Components: master
> Affects Versions: 0.90.3
> Reporter: Jieshan Bean
> Fix For: 0.90.7
>
> Attachments: HBASE-4064-v1.patch, HBASE-4064_branch90V2.patch,
> disableflow.png
>
>
> 1. If there is a "rubbish" RegionState object with "PENDING_CLOSE" in
> regionsInTransition(The RegionState was remained by some exception which
> should be removed, that's why I called it as "rubbish" object), but the
> region is not currently assigned anywhere, TimeoutMonitor will fall into an
> endless loop:
> 2011-06-27 10:32:21,326 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> state=PENDING_CLOSE, ts=1309141555301
> 2011-06-27 10:32:21,326 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:32:21,438 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:32:21,441 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Attempted to unassign
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f. but it is
> not currently assigned anywhere
> 2011-06-27 10:32:31,207 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> state=PENDING_CLOSE, ts=1309141555301
> 2011-06-27 10:32:31,207 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:32:31,215 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:32:31,215 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Attempted to unassign
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f. but it is
> not currently assigned anywhere
> 2011-06-27 10:32:41,164 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> state=PENDING_CLOSE, ts=1309141555301
> 2011-06-27 10:32:41,164 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:32:41,172 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:32:41,172 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Attempted to unassign
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f. but it is
> not currently assigned anywhere
> .....
> 2 In the following scenario, two concurrent unassigning call of the same
> region may lead to the above problem:
> the first unassign call send rpc call success, the master watched the event
> of "RS_ZK_REGION_CLOSED", process this event, will create a
> ClosedRegionHandler to remove the state of the region in master.eg.
> while ClosedRegionHandler is running in
> "hbase.master.executor.closeregion.threads" thread (A), another unassign call
> of same region run in another thread(B).
> while thread B run "if (!regions.containsKey(region))", this.regions have
> the region info, now cpu switch to thread A.
> The thread A will remove the region from the sets of "this.regions" and
> "regionsInTransition", then switch to thread B. the thread B run continue,
> will throw an exception with the msg of "Server null returned
> java.lang.NullPointerException: Passed server is null for
> 9a6e26d40293663a79523c58315b930f", but without removing the new-adding
> RegionState from "regionsInTransition",and it can not be removed for ever.
> public void unassign(HRegionInfo region, boolean force) {
> LOG.debug("Starting unassignment of region " +
> region.getRegionNameAsString() + " (offlining)");
> synchronized (this.regions) {
> // Check if this region is currently assigned
> if (!regions.containsKey(region)) {
> LOG.debug("Attempted to unassign region " +
> region.getRegionNameAsString() + " but it is not " +
> "currently assigned anywhere");
> return;
> }
> }
> String encodedName = region.getEncodedName();
> // Grab the state of this region and synchronize on it
> RegionState state;
> long stamp = -1;
> synchronized (regionsInTransition) {
> state = regionsInTransition.get(encodedName);
> if (state == null) {
> state = new RegionState(region, RegionState.State.PENDING_CLOSE);
> stamp =state.getStamp();
> regionsInTransition.put(encodedName, state);
> } else if (force && state.isPendingClose()) {
> LOG.debug("Attempting to unassign region " +
> region.getRegionNameAsString() + " which is already pending close
> "
> + "but forcing an additional close");
> state.update(RegionState.State.PENDING_CLOSE);
> } else {
> LOG.debug("Attempting to unassign region " +
> region.getRegionNameAsString() + " but it is " +
> "already in transition (" + state.getState() + ")");
> return;
> }
> }
>
> // Send CLOSE RPC
> HServerInfo server = null;
> synchronized (this.regions) {
> server = regions.get(region);
> }
> }
> 2011-06-27 10:20:59,583 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:20:59,585 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Sent CLOSE to
> serverName=158-1-91-101,20020,1308983865292, load=(requests=0, regions=0,
> usedHeap=0, maxHeap=0) for region
> test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:22:15,299 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling new unassigned
> node: /hbase/unassigned/9a6e26d40293663a79523c58315b930f
> (region=test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.,
> server=158-1-91-101,20020,1308983865292, state=RS_ZK_REGION_CLOSED)
> 2011-06-27 10:22:15,299 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_CLOSED, server=158-1-91-101,20020,1308983865292,
> region=9a6e26d40293663a79523c58315b930f
> 2011-06-27 10:25:22,636 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> state=CLOSED, ts=1309141335247
> 2011-06-27 10:25:22,636 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region
> 9a6e26d40293663a79523c58315b930f has been CLOSED for too long, waiting on
> queued ClosedRegionHandler to run or server shutdown
> 2011-06-27 10:25:55,022 DEBUG
> org.apache.hadoop.hbase.master.handler.ClosedRegionHandler: Handling CLOSED
> event for 9a6e26d40293663a79523c58315b930f
> 2011-06-27 10:25:55,022 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Table being disabled so
> deleting ZK node and removing from regions in transition, skipping assignment
> of region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:25:55,022 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:20000-0x230ba8b85230036 Deleting existing unassigned node for
> 9a6e26d40293663a79523c58315b930f that is in expected state
> RS_ZK_REGION_CLOSED
> 2011-06-27 10:25:55,101 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:20000-0x230ba8b85230036 Successfully deleted unassigned node for
> region 9a6e26d40293663a79523c58315b930f in expected state RS_ZK_REGION_CLOSED
> 2011-06-27 10:25:55,301 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:25:55,302 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Server null returned
> java.lang.NullPointerException: Passed server is null for
> 9a6e26d40293663a79523c58315b930f
> 2011-06-27 10:32:21,326 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> state=PENDING_CLOSE, ts=1309141555301
> 2011-06-27 10:32:21,326 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> 2011-06-27 10:32:21,438 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f.
> (offlining)
> 2011-06-27 10:32:21,441 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Attempted to unassign
> region test2,070712,1308971310309.9a6e26d40293663a79523c58315b930f. but it is
> not currently assigned anywhere
> 3 The following scenario shows how the above problem 2 happened:
> (1)A table have a lot of regions, more than 70000 in my test.
> (2)Disable the table, if 'BulkDisabler.waitUntilDone' timeout,
> 'DisableTableHandler.process' will create another BulkDisabler object and
> start its thread pool. The region which was still online will call
> AssignmentManager.unassign again. so the same region
> "AssignmentManager.unassign" could be called concurrentlly more than 1.
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