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https://issues.apache.org/jira/browse/HBASE-20893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16559392#comment-16559392
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Allan Yang edited comment on HBASE-20893 at 7/27/18 7:50 AM:
-------------------------------------------------------------
{quote}Split does not support rollback at the
SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS stage
{quote}
[~stack]， the Split does support at the
SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS stage, as you can see from the code
{code:java}
case SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS:
// Doing nothing, in SPLIT_TABLE_REGION_CLOSE_PARENT_REGION,
// we will bring parent region online
break;
{code}
Actually, it does nothing here, since when the statemachine procedure is
rolling back, it will roll back every state backwards, so when the rollback
process reaches at state SPLIT_TABLE_REGION_CLOSE_PARENT_REGION, it will open
the parent region.
But, some procedure does not support rollback, e.g Assign/Unassign Procedure.
It will throw a UnsupportedOperationException, which is totally OK.(We do not
except the region to close or open again after rollback)
May we shouldn't throw a exception if we do not support rollback, just log a
message there. Otherwise, the ProcedureExecutor will print a "CODE-BUG" message
which is pretty scary.
But, there is truly a bug here,
{code:java}
@Override
protected void rollback(final TEnvironment env)
throws IOException, InterruptedException {
if (isEofState()) stateCount--;
try {
updateTimestamp();
rollbackState(env, getCurrentState());
stateCount--;
} finally {
updateTimestamp();
}
}
{code}
We need to decrease the stateCount when rolling back, so we can rollback for
the previous state correctly. But. since a exception is thrown, the decrease
for stateCount never happen. So ProcedureExecutor will continue to rollback for
only one state(the one throw a exception) until the end of the execution stack.
was (Author: allan163):
{quote}
Split does not support rollback at the SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS
stage
{quote}
[~stack]， the Split does support at the
SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS stage, as you can see from the code
{code}
case SPLIT_TABLE_REGIONS_CHECK_CLOSED_REGIONS:
// Doing nothing, in SPLIT_TABLE_REGION_CLOSE_PARENT_REGION,
// we will bring parent region online
break;
{code}
Actually, it does nothing here, since when the statemachine procedure is
rolling back, it will roll back every state backwards, so when the rollback
process reaches at state SPLIT_TABLE_REGION_CLOSE_PARENT_REGION, it will open
the parent region.
But, some procedure does not support rollback, e.g Assign/Unassign Procedure.
It will throw a UnsupportedOperationException, which is totally OK.(We do not
except the region to close or open again after rollback)
May we shouldn't throw a exception if we do not support rollback, just log a
message there. Otherwise, the ProcedureExecutor will print a "CODE-BUG" message
which is pretty scary.
But, there is truly a bug here,
{code}
@Override
protected void rollback(final TEnvironment env)
throws IOException, InterruptedException {
if (isEofState()) stateCount--;
try {
updateTimestamp();
rollbackState(env, getCurrentState());
stateCount--;
} finally {
updateTimestamp();
}
}
{code}
We need to decrease the stateCount when rolling back, so we can rollback for
the previous state correctly. But. since a exception is thrown, the decrease
for stateCount never happen. So ProcedureExecutor will continue to rollback for
only state until the end of the execution stack.
> Data loss if splitting region while ServerCrashProcedure executing
> ------------------------------------------------------------------
>
> Key: HBASE-20893
> URL: https://issues.apache.org/jira/browse/HBASE-20893
> Project: HBase
> Issue Type: Sub-task
> Affects Versions: 3.0.0, 2.1.0, 2.0.1
> Reporter: Allan Yang
> Assignee: Allan Yang
> Priority: Major
> Fix For: 3.0.0, 2.0.2, 2.2.0, 2.1.1
>
> Attachments: HBASE-20893-branch-2.0.addendum.patch,
> HBASE-20893.branch-2.0.001.patch, HBASE-20893.branch-2.0.002.patch,
> HBASE-20893.branch-2.0.003.patch, HBASE-20893.branch-2.0.004.patch,
> HBASE-20893.branch-2.0.005.patch
>
>
> Similar case as HBASE-20878.
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