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From Panos Geo <panospanos1...@outlook.com>
Subject Re: NiFi stops processing further flowfiles
Date Mon, 27 Nov 2017 06:33:34 GMT
Hello Joe,


Many thanks for your reply and for checking the stack dump. I was trying hard to remember
where I've read about the new implementation of the provenance repo. Thanks for the pointer.
We'll check it out to see if it yields more stable behaviour.


Cheers,

Panos


________________________________
From: Joe Witt <joe.witt@gmail.com>
Sent: Saturday, November 25, 2017 3:05 AM
To: users@nifi.apache.org
Subject: Re: NiFi stops processing further flowfiles

Panos

In looking at the previously attached stack dump it looks as though the provenance repository
might be in a live lock state with one of its threads.  The getSize call it is sitting on
has been seen before and fixed for some cases but perhaps not all.  There is a whole new provenance
repository you could switch to though which offers far faster and possibly more stable behavior
called the 'WriteAheadProvenanceRepository'.  You can switch to it and it will honor the old
data I believe.  To switch you just edit your nifi.properties file and where it said 'PersistentProvenanceRepository'
you change that classname to 'WriteAheadProvenanceRepository'.

Thanks
Joe

On Fri, Nov 24, 2017 at 1:59 PM, Juan Sequeiros <hellojuan@gmail.com<mailto:hellojuan@gmail.com>>
wrote:
Hi Panos,

The scheduling strategy defaults to timer driven on processors and I've always avoided using
event driven so if you are not purposely using it I would just leave that setting alone. It
even warns you that it is experimental.

Your thread count is shown on the UI or can be called through RestApi /nifi-api/flow/status

Thanks,

Juan

On Fri, Nov 24, 2017 at 1:24 PM Panos Geo <panospanos1983@outlook.com<mailto:panospanos1983@outlook.com>>
wrote:

Thanks for your reply Juan.


I have been using NiFi for almost 2 years now and didn't know about this setting. I 'll try
to increase it and see what happens 😊


Does it also make sense to increase the "Maximum Event Driven Thread Count"?


Finally, is there a way to monitor thread usage within NiFi?


Many thanks,

Panos


________________________________
From: Juan Sequeiros <hellojuan@gmail.com<mailto:hellojuan@gmail.com>>
Sent: Friday, November 24, 2017 4:50 PM
To: users@nifi.apache.org<mailto:users@nifi.apache.org>
Subject: Re: NiFi stops processing further flowfiles

Good afternoon,

My quick guess is you are running out of threads.
If your system can handle it increase the default "max thread" count found:

Left side controller settings > Maximum timer driven thread count

On Fri, Nov 24, 2017 at 10:47 AM Panos Geo <panospanos1983@outlook.com<mailto:panospanos1983@outlook.com>>
wrote:

Hello all,

We are running NiFi in a docker container that has roughly 500 processors running. These include
consuming messages (MQTT), interaction with a database and some data processing with execute
scripts. Our NiFi version is v.1.4.0 and this instance has 18GB of RAM with 12GB allocated
to Java heap.

Quite recently we increased the load of the incoming messages (1000messages/minute) that lead
to more files being queued and some backpressure. We then have experienced what appears to
be some kind of deadlock. NiFi stops processing any flowfiles and the processors running get
stuck (there is a thread running constantly; we see 1 at the top right corner of the processor).
If we try to stop these processors the icon gets changed to stop, but we now have 2 threads
stuck at the top right corner of the processor. We cannot start these processors again and
no other data flow is being processed unless we restart NiFi. We have experienced this multiple
times over the past week.

I am attaching a nifi dump in case it helps. Our nifi.properties is fairly standard (we just
have smaller retention periods for content and provenance).

Any thoughts? What can we do to debug this further?

Many thanks,
Panos

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