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From "Colin Patrick McCabe (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-3396) HDFS reads are hanging
Date Wed, 10 Dec 2014 23:19:12 GMT


Colin Patrick McCabe commented on ACCUMULO-3396:

Basically, I am wondering if you are hitting HDFS-7489.  It should be easy to check, just
drop this in your hdfs config.

> HDFS reads are hanging
> ----------------------
>                 Key: ACCUMULO-3396
>                 URL:
>             Project: Accumulo
>          Issue Type: Bug
>          Components: tserver
>    Affects Versions: 1.6.0, 1.6.1
>         Environment: rhel6 linux 2.6.32-279 (x86_64)
> java 1.7.0_67-b01
> hadoop CDH5.1.2, HA (2) federated (2) NN configuration
> large production cluster
>            Reporter: Eric Newton
>            Assignee: Eric Newton
>            Priority: Blocker
> On large clusters we are seeing various forms of HDFS reads hanging:
> Queries that never return.
> Major compactions that hang.
> Accumulo 1.6.1 incorporates detectors that report hanging major compactions and a monitor
display that reports scans by age.
> Stack traces show readers in and in org.apache.hadoop.ipc.Client.Call(
> Netstat results for the tablet server shows many connections with a single byte waiting
on the Recv-Q of the process, and no bytes waiting on the Send-Q.
> strace of the jvm shows the typical jvm thread noise (futex calls)
> jstack shows lots of read-requests to the NN.
> long-running MajC's do complete, albeit slowly.

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