[jira] [Commented] (FLINK-8707) Excessive amount of files opened by flink task manager

["Alon Galant (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-8707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16468809#comment-16468809 ] 

Alon Galant commented on FLINK-8707:
------------------------------------

Thanks Nico.

My problem is solved :)

We run Flink over Supervisor, and it turns out that Supervisor overrides the Max open files per supervisor job, which can be changed in its config file.

I found out you can check Max open file for process with {{$cat /proc/<pid>/limits}}, and I got different numbers than with {{ulimit -a}}.

Running {{lsof -p <pid>}} gave around 3000 open FDs, which is much better than a million :)

The default value of Supervisor was 4096, so I guess that in time of heavy traffic, the real number of open files was higher that this, and that's why we've got the Too many open files exception.

 

Thanks,

Alon

 

> Excessive amount of files opened by flink task manager
> ------------------------------------------------------
>
>                 Key: FLINK-8707
>                 URL: https://issues.apache.org/jira/browse/FLINK-8707
>             Project: Flink
>          Issue Type: Bug
>          Components: TaskManager
>    Affects Versions: 1.3.2
>         Environment: NAME="Red Hat Enterprise Linux Server"
> VERSION="7.3 (Maipo)"
> Two boxes, each with a Job Manager & Task Manager, using Zookeeper for HA.
> flink.yaml below with some settings (removed exact box names) etc:
> env.log.dir: ...some dir...residing on the same box
> env.pid.dir: some dir...residing on the same box
> metrics.reporter.jmx.class: org.apache.flink.metrics.jmx.JMXReporter
> metrics.reporters: jmx
> state.backend: filesystem
> state.backend.fs.checkpointdir: file:///some_nfs_mount
> state.checkpoints.dir: file:///some_nfs_mount
> state.checkpoints.num-retained: 3
> high-availability.cluster-id: /tst
> high-availability.storageDir: file:///some_nfs_mount/ha
> high-availability: zookeeper
> high-availability.zookeeper.path.root: /flink
> high-availability.zookeeper.quorum: ...list of zookeeper boxes
> env.java.opts.jobmanager: ...some extra jar args
> jobmanager.archive.fs.dir: some dir...residing on the same box
> jobmanager.web.submit.enable: true
> jobmanager.web.tmpdir:  some dir...residing on the same box
> env.java.opts.taskmanager: some extra jar args
> taskmanager.tmp.dirs:  some dir...residing on the same box/var/tmp
> taskmanager.network.memory.min: 1024MB
> taskmanager.network.memory.max: 2048MB
> blob.storage.directory:  some dir...residing on the same box
>            Reporter: Alexander Gardner
>            Priority: Critical
>             Fix For: 1.5.0
>
>         Attachments: AfterRunning-3-jobs-Box2-TM-JCONSOLE.png, AfterRunning-3-jobs-TM-FDs-BOX2.jpg, AfterRunning-3-jobs-lsof-p.box2-TM, AfterRunning-3-jobs-lsof.box2-TM, AterRunning-3-jobs-Box1-TM-JCONSOLE.png, box1-jobmgr-lsof, box1-taskmgr-lsof, box2-jobmgr-lsof, box2-taskmgr-lsof, ll.txt, ll.txt, lsof.txt, lsof.txt, lsofp.txt, lsofp.txt
>
>
> The job manager has less FDs than the task manager.
>  
> Hi
> A support alert indicated that there were a lot of open files for the boxes running Flink.
> There were 4 flink jobs that were dormant but had consumed a number of msgs from Kafka using the FlinkKafkaConsumer010.
> A simple general lsof:
> $ lsof | wc -l       ->  returned 153114 open file descriptors.
> Focusing on the TaskManager process (process ID = 12154):
> $ lsof | grep 12154 | wc -l-    > returned 129322 open FDs
> $ lsof -p 12154 | wc -l   -> returned 531 FDs
> There were 228 threads running for the task manager.
>  
> Drilling down a bit further, looking at a_inode and FIFO entries: 
> $ lsof -p 12154 | grep a_inode | wc -l = 100 FDs
> $ lsof -p 12154 | grep FIFO | wc -l  = 200 FDs
> $ /proc/12154/maps = 920 entries.
> Apart from lsof identifying lots of JARs and SOs being referenced there were also 244 child processes for the task manager process.
> Noticed that in each environment, a creep of file descriptors...are the above figures deemed excessive for the no of FDs in use? I know Flink uses Netty - is it using a separate Selector for reads & writes? 
> Additionally Flink uses memory mapped files? or direct bytebuffers are these skewing the numbers of FDs shown?
> Example of one child process ID 6633:
> java 12154 6633 dfdev 387u a_inode 0,9 0 5869 [eventpoll]
>  java 12154 6633 dfdev 388r FIFO 0,8 0t0 459758080 pipe
>  java 12154 6633 dfdev 389w FIFO 0,8 0t0 459758080 pipe
> Lasty, cannot identify yet the reason for the creep in FDs even if Flink is pretty dormant or has dormant jobs. Production nodes are not experiencing excessive amounts of throughput yet either.
>  
>  
>  



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