[ https://issues.apache.org/jira/browse/TEZ-3974?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Gopal V updated TEZ-3974:
-------------------------
Attachment: TEZ-3974.3.patch
> Tez: Correctness regression of TEZ-955 in TEZ-2937
> --------------------------------------------------
>
> Key: TEZ-3974
> URL: https://issues.apache.org/jira/browse/TEZ-3974
> Project: Apache Tez
> Issue Type: Bug
> Reporter: Gopal V
> Assignee: Gopal V
> Priority: Critical
> Attachments: TEZ-3974.1.patch, TEZ-3974.2.patch, TEZ-3974.3.patch
>
>
> TEZ-2937 might have introduced a race condition for Tez output events, along with TEZ-2237
> {code}
> // Close the Outputs.
> for (OutputSpec outputSpec : outputSpecs) {
> String destVertexName = outputSpec.getDestinationVertexName();
> initializedOutputs.remove(destVertexName);
> List<Event> closeOutputEvents = ((LogicalOutputFrameworkInterface)outputsMap.get(destVertexName)).close();
> sendTaskGeneratedEvents(closeOutputEvents,
> EventProducerConsumerType.OUTPUT, taskSpec.getVertexName(),
> destVertexName, taskSpec.getTaskAttemptID());
> }
> // Close the Processor.
> processorClosed = true;
> processor.close();
> {code}
> As part of TEZ-2237, the outputs send empty events when the output is closed without
being started (which happens in task init failures).
> These events are obsoleted when a task fails and this happens in the AM, but not before
the dispatcher looks at them.
> Depending on the timing, the empty events can escape obsoletion & be sent to a downstream
task.
> This gets marked as a SKIPPED event in the downstream task, which means that further
obsoletion events sent to the downstream task is ignored (because a zero byte fetch is not
repeated on node failure).
> So the downstream task can exit without actually waiting for the retry of the failed
task and cause silent dataloss in case where the retry succeeds in another attempt.
> So if processor.close() throws an exception, this introduce a race condition and if the
AM is too fast, we end up with correctness issues.
> This was originally reported in TEZ-955
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
|