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https://issues.apache.org/jira/browse/HBASE-4064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13412363#comment-13412363
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Jonathan Hsieh commented on HBASE-4064:
---------------------------------------
There was some recent activity here, anyone planning on finishing this guy?
(its been bumped a few times considering bumping it for the 0.90.7 release).
> 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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