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https://issues.apache.org/jira/browse/HBASE-6060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13291755#comment-13291755
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ramkrishna.s.vasudevan commented on HBASE-6060:
-----------------------------------------------
@Stack
Just to reiterate this JIRA is a backport of HBASE-5396. The current patch
that you gave is similar to HBASE-5396 and it will solve the problem of
assigning a region that has started opening in a RS but the RS went down.
But if we don't have any common sharing between AM and SSH
{code}
RegionPlan regionPlan = getRegionPlan(regionState, sn, true);
{code}
In the first assign call we form a regionplan. It so happened that we got the
plan and issued sendRegionOpen(). By the time the RS had gone down. Now as
per your patch(HBASE-5396) the SSH will trigger and he will start a new
assignment. At the same time
{code}
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 null if no servers.
RegionPlan newPlan = getRegionPlan(state,
plan.getDestination(), true);
if (isNullPlan(newPlan, state, plan.getDestination())) {
// Whether no servers to assign too or region assignment is
being handled elsewhere,
// skip out of this retry loop.
break;
{code}
Excluding this server we will call one more assign because of retry logic. And
that is where there is a chance of getting the master abort problem. In the
current patch that u gave getRegionPlan will create the above problem.
This is where we need to have a common structure and also a new state of region
plan to say whether to make another assign call or not thro AM.
{code}
if (!hijack && !state.isClosed() && !state.isOffline()) {
String msg = "Unexpected state : " + state + " .. Cannot transit it to
OFFLINE.";
this.master.abort(msg, new IllegalStateException(msg));
return -1;
}
{code}
Now the problem of master abort was reported in HBASE-5816.(Because HBASE-5396
is committed to 0.90). Now what we are doing is to solve this as a whole so
that we don't end up in any double assignment or any problem with master abort.
One more problem in patch is 'outstandingRegionPlans' should be cleared here
{code}
} else if (addressFromAM != null && !addressFromAM.equals(this.serverName)) {
+ LOG.debug("Skip assigning region " +
e.getKey().getRegionNameAsString()
+ + " because it has been opened in " +
addressFromAM.getServerName());
+ }
{code}
STack i feel that sharing something common is necessary to avoid this problem.
Just to add, HBASE-6147 i have given one patch, which when combined with the
patch here will solve many other issues also.
Do let me know if you still feel there are some more doubts on this?
> Regions's in OPENING state from failed regionservers takes a long time to
> recover
> ---------------------------------------------------------------------------------
>
> Key: HBASE-6060
> URL: https://issues.apache.org/jira/browse/HBASE-6060
> Project: HBase
> Issue Type: Bug
> Components: master, regionserver
> Reporter: Enis Soztutar
> Assignee: rajeshbabu
> Fix For: 0.96.0, 0.94.1, 0.92.3
>
> Attachments: 6060-94-v3.patch, 6060-94-v4.patch, 6060-94-v4_1.patch,
> 6060-94-v4_1.patch, 6060-trunk.patch, 6060-trunk.patch, 6060-trunk_2.patch,
> 6060-trunk_3.patch, 6060_suggestion2_based_off_v3.patch,
> 6060_suggestion_based_off_v3.patch, HBASE-6060-92.patch, HBASE-6060-94.patch
>
>
> we have seen a pattern in tests, that the regions are stuck in OPENING state
> for a very long time when the region server who is opening the region fails.
> My understanding of the process:
>
> - master calls rs to open the region. If rs is offline, a new plan is
> generated (a new rs is chosen). RegionState is set to PENDING_OPEN (only in
> master memory, zk still shows OFFLINE). See HRegionServer.openRegion(),
> HMaster.assign()
> - RegionServer, starts opening a region, changes the state in znode. But
> that znode is not ephemeral. (see ZkAssign)
> - Rs transitions zk node from OFFLINE to OPENING. See
> OpenRegionHandler.process()
> - rs then opens the region, and changes znode from OPENING to OPENED
> - when rs is killed between OPENING and OPENED states, then zk shows OPENING
> state, and the master just waits for rs to change the region state, but since
> rs is down, that wont happen.
> - There is a AssignmentManager.TimeoutMonitor, which does exactly guard
> against these kind of conditions. It periodically checks (every 10 sec by
> default) the regions in transition to see whether they timedout
> (hbase.master.assignment.timeoutmonitor.timeout). Default timeout is 30 min,
> which explains what you and I are seeing.
> - ServerShutdownHandler in Master does not reassign regions in OPENING
> state, although it handles other states.
> Lowering that threshold from the configuration is one option, but still I
> think we can do better.
> Will investigate more.
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