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https://issues.apache.org/jira/browse/STORM-770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14562091#comment-14562091
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Jungtaek Lim commented on STORM-770:
------------------------------------
[~fhussonnois]
Thanks for information! I think I'm too late to comment.
Actually there're some issues with documentation.
http://storm.apache.org/documentation/Concepts.html says
{quote}
Its perfectly fine to launch new threads in bolts that do processing
asynchronously. OutputCollector is thread-safe and can be called at any time.
{quote}
and http://storm.apache.org/documentation/Troubleshooting.html says
{quote}
This is caused by having multiple threads issue methods on the OutputCollector.
All emits, acks, and fails must happen on the same thread. One subtle way this
can happen is if you make a IBasicBolt that emits on a separate thread.
IBasicBolt's automatically ack after execute is called, so this would cause
multiple threads to use the OutputCollector leading to this exception. When
using a basic bolt, all emits must happen in the same thread that runs execute.
{quote}
It is a contradiction, and at least for now OutputCollector is not thread-safe.
https://www.mail-archive.com/[email protected]/msg00939.html
> NullPointerException in consumeBatchToCursor
> --------------------------------------------
>
> Key: STORM-770
> URL: https://issues.apache.org/jira/browse/STORM-770
> Project: Apache Storm
> Issue Type: Bug
> Affects Versions: 0.9.2-incubating
> Reporter: Stas Levin
>
> We got the following exception after our topology had been up for ~2 days,
> and I was wondering if it might be related.
> Looks like "task" in "mk-transfer-fn" is null, making "(.add remote
> (TaskMessage. task (.serialize serializer tuple)))" fail on NPE
> (worker.clj:128, storm-core-0.9.2-incubating.jar)
> java.lang.RuntimeException: java.lang.NullPointerException
> at
> backtype.storm.utils.DisruptorQueue.consumeBatchToCursor(DisruptorQueue.java:128)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.utils.DisruptorQueue.consumeBatchWhenAvailable(DisruptorQueue.java:99)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.disruptor$consume_batch_when_available.invoke(disruptor.clj:80)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.disruptor$consume_loop_STAR_$fn__758.invoke(disruptor.clj:94)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at backtype.storm.util$async_loop$fn__457.invoke(util.clj:431)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at clojure.lang.AFn.run(AFn.java:24) [clojure-1.5.1.jar:na]
> at java.lang.Thread.run(Thread.java:745) [na:1.7.0_72]
> Caused by: java.lang.NullPointerException: null
> at clojure.lang.RT.intCast(RT.java:1087) ~[clojure-1.5.1.jar:na]
> at
> backtype.storm.daemon.worker$mk_transfer_fn$fn__5748.invoke(worker.clj:128)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.daemon.executor$start_batch_transfer_GT_worker_handler_BANG$fn__5483.invoke(executor.clj:256)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.disruptor$clojure_handler$reify__745.onEvent(disruptor.clj:58)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> at
> backtype.storm.utils.DisruptorQueue.consumeBatchToCursor(DisruptorQueue.java:125)
> ~[storm-core-0.9.2-incubating.jar:0.9.2-incubating]
> ... 6 common frames omitted,java.lang.RuntimeException:
> java.lang.NullPointerException
> Any ideas?
> P.S.
> Also saw it here:
> http://mail-archives.apache.org/mod_mbox/storm-user/201501.mbox/%3CCABcMBhCusXXU=v1e66wfuatgyh1euqnd1siog65-tp8xlwx...@mail.gmail.com%3E
> https://mail-archives.apache.org/mod_mbox/storm-user/201408.mbox/%3ccajuqm_4kxhsh2_x08ujuqr76m2c+dswp0fcijbmfcaeyqgs...@mail.gmail.com%3E
> Comment from Bobby
> http://mail-archives.apache.org/mod_mbox/storm-user/201501.mbox/%3c574363643.2791948.1420470097280.javamail.ya...@jws10027.mail.ne1.yahoo.com%3E
> {quote}
> What version of storm are you using? Are any of the bolts shell bolts?
> There is a known
> issue where this can happen if two shell bolts share an executor, because
> they are multi-threaded.
> - Bobby
> {quote}
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