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From Chesnay Schepler <ches...@apache.org>
Subject Re: Flink metrics related problems/questions
Date Mon, 22 May 2017 13:08:07 GMT
Yes, that could cause the observed issue.

The default implementations are not thread-safe; if you do concurrent 
writes they may be lost/overwritten.
You will have to either guard accesses to that metric with a 
synchronized block or implement your own thread-safe counter.

On 22.05.2017 14:17, Aljoscha Krettek wrote:
> @Chesnay With timers it will happen that onTimer() is called from a different Thread
than the Tread that is calling processElement(). If Metrics updates happen in both, would
that be a problem?
>> On 19. May 2017, at 11:57, Chesnay Schepler <chesnay@apache.org> wrote:
>> 2. isn't quite accurate actually; metrics on the TaskManager are not persisted across
>> On 19.05.2017 11:21, Chesnay Schepler wrote:
>>> 1. This shouldn't happen. Do you access the counter from different threads?
>>> 2. Metrics in general are not persisted across restarts, and there is no way
to configure flink to do so at the moment.
>>> 3. Counters are sent as gauges since as far as I know StatsD counters are not
allowed to be decremented.
>>> On 19.05.2017 08:56, jaxbihani wrote:
>>>> Background: We are using a job using ProcessFunction which reads data from
>>>> kafka fires ~5-10K timers per second and sends matched events to KafkaSink.
>>>> We are collecting metrics for collecting no of active timers, no of timers
>>>> scheduled etc. We use statsd reporter and monitor using Grafana dashboard
>>>> RocksDBStateBackend backed by HDFS as state.
>>>> Observations/Problems:
>>>> 1. *Counter value suddenly got reset:*  While job was running fine, on one
>>>> fine moment, metric of a monotonically increasing counter (Counter where
>>>> just used inc() operation) suddenly became 0 and then resumed from there
>>>> onwards. Only exception in the logs were related to transient connectivity
>>>> issues to datanodes. Also there was no other indicator of any failure
>>>> observed after inspecting system metrics/checkpoint metrics.  It happened
>>>> just once across multiple runs of a same job.
>>>> 2. *Counters not retained during flink restart with savepoint*: Cancelled
>>>> job with -s option taking savepoint and then restarted the job using the
>>>> savepoint.  After restart metrics started from 0. I was expecting metric
>>>> value of a given operator would also be part of state.
>>>> 3. *Counter metrics getting sent as Gauge*: Using tcpdump I was inspecting
>>>> the format in which metric are sent to statsd. I observed that even the
>>>> metric which in my code were counters, were sent as gauges. I didn't get
>>>> that was so.
>>>> Can anyone please add more insights into why above mentioned behaviors would
>>>> have happened?
>>>> Also does flink store metric values as a part of state for stateful
>>>> operators? Is there any way to configure that?
>>>> -- 
>>>> View this message in context: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Flink-metrics-related-problems-questions-tp13218.html
>>>> Sent from the Apache Flink User Mailing List archive. mailing list archive
at Nabble.com.

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