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From Aaron Longfield <>
Subject Re: Nifi cluster nodes regularly stop processing any flowfiles
Date Mon, 01 Aug 2016 14:19:22 GMT
I've been trying different things to try to fix my NiFi freeze problems,
and it seems the most frequent reason that my cluster gets stuck and stops
processing has to do with network related processors.  My data enters the
environment from Kafka and leaves via a site-to-site output port.  After
some time processing (sometimes a few minutes, sometimes a few hours) one
of those will start logging connection errors, and then that node will stop
processing any flowfiles across all processors.

So far, this followed me from 0.6.1 to 0.7.0, and on Amazon Linux to RHEL7
(although RHEL seems to be happier).  I've tried restricting threads to
less than the number of available cores on each node, different heap sizes,
and different garbage collectors.  So far none of that has preventing the
problem, unfortunately.

I'm not quite ready to build all custom processors for my flow logic...
most of it is straightforward attribute routing, text replacement, and
flowfile merging.

What are other things that I could try, or just be doing wrong that could
lead to this?  I'm happy to keep trying suggestions and changes; I really
want this to work!


On Fri, Jul 15, 2016 at 12:07 PM, Lee Laim <> wrote:

> Aaron,
> I ran into an issue where the Execute Stream Command (ESC) processor with
> many threads would run a legacy script that would hang if the incoming file
> was 'inconsistent'.  It appeared that ESC slowly collected stuck threads as
> malformed data randomly streamed through it. Eventually I ran out of
> threads as the system was just waiting for a thread to become available.
> It was apparent in the processor statistics where the flowfiles-out
> statistic would eventually step down to zero as threads became stuck.
> It might be worth trying InvokeScriptedProcessor or building custom
> processors as they provide a means to handle these inconsistencies more
> gracefully.
> Thanks,
> Lee
> On Fri, Jul 15, 2016 at 6:50 AM, Aaron Longfield <>
> wrote:
>> Hi Mark,
>> I've been using the G1 garbage collector.  I brought the nodes down to
>> 8GB heap and let it run overnight, but processing still got stuck and
>> requiring NiFi to be restarted on all nodes.  It took longer to happen, but
>> they went down after a few hours.  Are there any other things I can look
>> into?
>> Thanks!
>> -Aaron
>> On Thu, Jul 14, 2016 at 2:33 PM, Mark Payne <> wrote:
>>> Aaron,
>>> My guess would be that you are hitting a Full Garbage Collection. With
>>> such a huge Java heap, that will cause a "stop the world" pause for quite a
>>> long time.
>>> Which garbage collector are you using? Have you tried reducing the heap
>>> from 48 GB to say 4 or 8 GB?
>>> Thanks
>>> -Mark
>>> > On Jul 14, 2016, at 11:14 AM, Aaron Longfield <>
>>> wrote:
>>> >
>>> > Hi,
>>> >
>>> > I'm having an issue with a small (two node) NiFi cluster where the
>>> nodes will stop processing any queued flowfiles.  I haven't seen any error
>>> messages logged related to it, and when attempting to restart the service,
>>> NiFi doesn't respond and the script forcibly kills it.  This causes
>>> multiple flowfile version to hang around, and generally makes me feel like
>>> it might be causing data loss.
>>> >
>>> > I'm running the web UI on a different box, and when things stop
>>> working, it stops showing changes to counts in any queues, and the thread
>>> count never changes.  It still thinks the nodes are connecting and
>>> responding, though.
>>> >
>>> > My environment is two 8 cpu systems w/ 60GB memory with 48GB given to
>>> the NiFi JVM in bootstrap.conf.  I have timer threads limited to 12, and
>>> event threads to 4.  Install is on the current Amazon Linux AMI and using
>>> OpenJDK x64.
>>> >
>>> > Any idea, other debug steps, or changes that I can try?  I'm running
>>> 0.7.0, having upgraded from 0.6.1, but this has been occurring with both
>>> versions.  The higher the flowfile volume I push through, the faster this
>>> happens.
>>> >
>>> > Thanks for any help there is to give!
>>> >
>>> > -Aaron Longfield

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