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https://issues.apache.org/jira/browse/NIFI-16311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18113587#comment-18113587
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ASF subversion and git services commented on NIFI-16311:
--------------------------------------------------------
Commit 68a6149ca067076fb0f3fe0f5a78b1ded6c2f4a1 in nifi's branch
refs/heads/NIFI-16315 from Joe Witt
[ https://gitbox.apache.org/repos/asf?p=nifi.git;h=68a6149ca06 ]
NIFI-16311 Initialize ParseSyslog parser in @OnScheduled (#11639)
CHARSET cannot change between triggers, so lazy construction in onTrigger was
an unsynchronized check-then-act on the shared processor instance. Match
ParseSyslog5424: build once at schedule time and publish the parser as volatile.
> ParseSyslog initializes SyslogParser unsafely under concurrent tasks
> --------------------------------------------------------------------
>
> Key: NIFI-16311
> URL: https://issues.apache.org/jira/browse/NIFI-16311
> Project: Apache NiFi
> Issue Type: Bug
> Components: Extensions
> Reporter: Joe Witt
> Assignee: Joe Witt
> Priority: Major
> Fix For: 2.12.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> ParseSyslog keeps a SyslogParser in a non-volatile instance field and lazily
> constructs it inside onTrigger:
> if (parser == null || !parser.getCharsetName().equals(charsetName)) {
> parser = new SyslogParser(Charset.forName(charsetName));
> }
> NiFi uses a single processor instance for all concurrent tasks, so this is an
> unsynchronized check-then-act. A second thread can observe a non-null parser
> whose charset has not been published, or two threads can replace the field
> while parseEvent is running.
> The Character Set property does not support Expression Language, so its value
> cannot change between triggers. The per-trigger re-init is unnecessary.
> ParseSyslog5424 already does this correctly: it builds the parser in
> @OnScheduled and stores it in a volatile field.
> This ticket is only that lifecycle/concurrency fix. It does not change
> parsing, relationships, or how FlowFile content is read.
> Expected:
> - SyslogParser is created once when the processor is scheduled
> - Concurrent tasks share a safely published, immutable-for-the-run parser
> - Existing RFC3164/RFC5424 parse tests still pass
> - A TestRunner test with concurrent tasks succeeds
> Actual:
> - Parser construction races in onTrigger when Concurrent Tasks > 1
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