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https://issues.apache.org/jira/browse/BEAM-8347?focusedWorklogId=337875&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-337875
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ASF GitHub Bot logged work on BEAM-8347:
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Author: ASF GitHub Bot
Created on: 03/Nov/19 23:34
Start Date: 03/Nov/19 23:34
Worklog Time Spent: 10m
Work Description: drobert commented on issue #9820: [BEAM-8347]:
Consistently advance UnboundedRabbitMqReader watermark
URL: https://github.com/apache/beam/pull/9820#issuecomment-549189280
Update: after running some tests, the migration to the pull-based API in
https://github.com/apache/beam/pull/9900 proves to be unsafe for this use case.
I misread or misunderstood the semantics but it seems `channel.basicGet` blocks
indefinitely, as opposed to returning immediately if there are no messages.
This means if no new messages come in for a long period of time, the Runner
will detect that the reader is 'stuck' since it's been on a single blocking
call for so many minutes. Basically, we need to revert to a
push-based-but-blocking API for this.
*However* that is a separate issue from the watermarks advancing. I don't
think that broken merge should block this PR once rebased. PR for that issue is
here: https://github.com/apache/beam/pull/9977
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Issue Time Tracking
-------------------
Worklog Id: (was: 337875)
Time Spent: 3h (was: 2h 50m)
> UnboundedRabbitMqReader can fail to advance watermark if no new data comes in
> -----------------------------------------------------------------------------
>
> Key: BEAM-8347
> URL: https://issues.apache.org/jira/browse/BEAM-8347
> Project: Beam
> Issue Type: Bug
> Components: io-java-rabbitmq
> Affects Versions: 2.15.0
> Environment: testing has been done using the DirectRunner. I also
> have DataflowRunner available
> Reporter: Daniel Robert
> Assignee: Jean-Baptiste Onofré
> Priority: Major
> Time Spent: 3h
> Remaining Estimate: 0h
>
> I stumbled upon this and then saw a similar StackOverflow post:
> [https://stackoverflow.com/questions/55736593/apache-beam-rabbitmqio-watermark-doesnt-advance]
> When calling `advance()` if there are no messages, no state changes,
> including no changes to the CheckpointMark or Watermark. If there is a
> relatively constant rate of new messages coming in, this is not a problem. If
> data is bursty, and there are periods of no new messages coming in, the
> watermark will never advance.
> Contrast this with some of the logic in PubsubIO which will make provisions
> for periods of inactivity to advance the watermark (although it, too, is
> imperfect: https://issues.apache.org/jira/browse/BEAM-7322 )
> The example given in the StackOverflow post is something like this:
>
> {code:java}
> pipeline
> .apply(RabbitMqIO.read()
> .withUri("amqp://guest:guest@localhost:5672")
> .withQueue("test")
> .apply("Windowing",
> Window.<RabbitMqMessage>into(
> FixedWindows.of(Duration.standardSeconds(10)))
> .triggering(AfterWatermark.pastEndOfWindow())
> .withAllowedLateness(Duration.ZERO)
> .accumulatingFiredPanes()){code}
> If I push 2 messages into my rabbit queue, I see 2 unack'd messages and a
> window that never performs an on time trigger.
>
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