[jira] [Resolved] (CASSANDRA-13133) Unclosed file descriptors when querying SnapshotsSize metric

["Nicholas Rushton (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-13133?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nicholas Rushton resolved CASSANDRA-13133.
------------------------------------------
    Resolution: Fixed

fixed by CASSANDRA-11594

> Unclosed file descriptors when querying SnapshotsSize metric
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-13133
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13133
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Local Write-Read Paths
>         Environment: CentOS 7
>            Reporter: Nicholas Rushton
>              Labels: jmx, lhf, metrics, newbie
>             Fix For: 3.9
>
>
> Started to notice many open file descriptors (100k+) per node, growing at a rate of about 30 per minute in our cluster. After turning off our JMX exporting server(https://github.com/prometheus/jmx_exporter), which gets queried every 30 seconds, the number of file descriptors remained static. 
> Digging a bit further I ran a jmx dump tool over all the cassandra metrics and tracked the number of file descriptors after each query, boiling it down to a single metric causing the number of file descriptors to increase:
> org.apache.cassandra.metrics:keyspace=tpsv1,name=SnapshotsSize,scope=events_by_engagement_id,type=Table
> running a query a few times against this metric shows the file descriptors increasing after each query:
> {code}
> for _ in {0..3} 
> do 
>    java -jar jmx-dump-0.4.2-standalone.jar --port 7199 --dump org.apache.cassandra.metrics:keyspace=tpsv1,name=SnapshotsSize,scope=events_by_engagement_id,type=Table > /dev/null; 
>    sudo lsof -p `pgrep -f CassandraDaemon` | fgrep "DIR" | awk '{a[$(NF)]+=1}END{for(k in a){print k, a[k]}}' | grep "events_by" 
> done
> > /data/cassandra/data/tpsv1/events_by_engagement_id-01d8f450a54911e6917ec93f8a91ec71 33176
> > /data/cassandra/data/tpsv1/events_by_engagement_id-01d8f450a54911e6917ec93f8a91ec71 33177
> > /data/cassandra/data/tpsv1/events_by_engagement_id-01d8f450a54911e6917ec93f8a91ec71 33178
> > /data/cassandra/data/tpsv1/events_by_engagement_id-01d8f450a54911e6917ec93f8a91ec71 33179
> {code}
> it should be noted that the file descriptor is open on a directory, not an actual file



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