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https://issues.apache.org/jira/browse/FLINK-21132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17276558#comment-17276558
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Kezhu Wang commented on FLINK-21132:
------------------------------------
Currently, there is no {{runSynchronousSavepointMailboxLoop}} in
{{StreamTask.triggerCheckpoint}}, but let's assume it has.
For mailbox tasks, it will not handle any mail until checkpoint confirmation.
After checkpoint completion, poison mail will break out mailbox loop. I did not
find a hole in between since there is no chance to read/write.
For legacy source, thing get complicated. I would like to list an example body
for {{SourceFunction}}:
{code:java}
public void run(SourceContext<T> ctx) {
while (isRunning && condition) {
// this synchronized block ensures that state checkpointing,
// internal state updates and emission of elements are an atomic
operation
synchronized (ctx.getCheckpointLock()) {
ctx.collect(count);
count++;
}
}
}
{code}
# If checkpoint comes before {{synchronized}}, after checkpoint completion,
{{ctx.collect}} will throw exception, but it is covered by {{isStopped()}} in
{{SourceStreamTask}}, and exception is ignored in this case.
# If checkpoint comes after {{synchronized}} and source function run out, it
could finish the thread which cause poison mail. But poison mail actually only
break out mailbox loop itself, but not {{MailboxExecutor.yield}} loop. So still
wait for checkpoint completion, and from now, it is actually same as mailbox
tasks as there is no concurrent thread now. The only hole I saw is in
{{StreamSource}}, where executes endInput after {{SourceFunction.run}}. I think
we could move it to {{SourceStreamTask.afterInvoke}} if we want to keep this
theoretical possibility.
I think some of above apply to eop-detection approach too, hope it could help.
> BoundedOneInput.endInput is called when taking synchronous savepoint
> --------------------------------------------------------------------
>
> Key: FLINK-21132
> URL: https://issues.apache.org/jira/browse/FLINK-21132
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Task
> Affects Versions: 1.10.2, 1.10.3, 1.11.3, 1.12.1
> Reporter: Kezhu Wang
> Assignee: Roman Khachatryan
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.11.4, 1.12.2, 1.13.0
>
>
> [~elkhand](?) reported on project iceberg that {{BoundedOneInput.endInput}}
> was
> [called|https://github.com/apache/iceberg/issues/2033#issuecomment-765864038]
> when [stopping job with
> savepoint|https://github.com/apache/iceberg/issues/2033#issuecomment-765557995].
> I think it is a bug of Flink and was introduced in FLINK-14230. The
> [changes|https://github.com/apache/flink/pull/9854/files#diff-0c5fe245445b932fa83fdaf5c4802dbe671b73e8d76f39058c6eaaaffd9639faL577]
> rely on {{StreamTask.afterInvoke}} and {{OperatorChain.closeOperators}} will
> only be invoked after *end of input*. But that is not true long before after
> [FLIP-34: Terminate/Suspend Job with
> Savepoint|https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=103090212].
> Task could enter state called
> [*finished*|https://github.com/apache/flink/blob/3a8e06cd16480eacbbf0c10f36b8c79a6f741814/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/StreamTask.java#L467]
> after synchronous savepoint, that is an expected job suspension and stopping.
> [~sunhaibotb] [~pnowojski] [~roman_khachatryan] Could you help confirm this ?
> For full context, see
> [apache/iceberg#2033|https://github.com/apache/iceberg/issues/2033]. I have
> pushed branch
> [synchronous-savepoint-conflict-with-bounded-end-input-case|https://github.com/kezhuw/flink/commits/synchronous-savepoint-conflict-with-bounded-end-input-case]
> in my repository. Test case
> {{SavepointITCase.testStopSavepointWithBoundedInput}} failed due to
> {{BoundedOneInput.endInput}} called.
> I am also aware of [FLIP-147: Support Checkpoints After Tasks
> Finished|https://cwiki.apache.org/confluence/x/mw-ZCQ], maybe the three
> should align on what *finished* means exactly. [~kkl0u] [~chesnay]
> [~gaoyunhaii]
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