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From "Akira Ajisaka (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-15477) Make unjar in RunJar overrideable
Date Mon, 28 May 2018 08:38:00 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-15477?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Akira Ajisaka updated HADOOP-15477:
-----------------------------------
    Environment: If {{HADOOP_CLIENT_SKIP_UNJAR}} environment variable is set to true, Apache
Hadoop RunJar skips unjar the provided jar.

> Make unjar in RunJar overrideable
> ---------------------------------
>
>                 Key: HADOOP-15477
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15477
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 2.8.3, 2.9.1, 2.7.6, 3.0.2
>         Environment: If {{HADOOP_CLIENT_SKIP_UNJAR}} environment variable is set to true,
Apache Hadoop RunJar skips unjar the provided jar.
>            Reporter: Johan Gustavsson
>            Assignee: Johan Gustavsson
>            Priority: Trivial
>             Fix For: 3.2.0
>
>         Attachments: HADOOP-15477.001.patch, HADOOP-15477.002.patch, HADOOP-15477.003.patch,
HADOOP-15477.004.patch
>
>
> Currently Hadoop's RunJar will unjar the jar provided and look for any jars inside and
add them to the classpath. Since most deployments doesn't use jar in jar, but rather uberjars
this could be rather time consuming at times and can cause issues related to over consumption of
inodes, for something that is in many cases is not used.
> For that purpose there should be an env variable to disable this behavior.
>  
> Edit: As requested by [~ajisakaa] in person here is a more detailed description of the
issues we are trying to solve with this.
> A good chunk of our workloads are packaged in an uberjar, and are launched as a separate
process using the {{hadoop jar}} cli. This is has generally been working out pretty well
historically, with sub second launch times and good client isolation. Since bumping the
host OS to a version patched with Meltdown/Specter patches we do see from time to time load
becoming very high even with only a few client processes running and a single unjar process
taking up to 10min. 
> While another simple approach would be to abandon using the {{hadoop jar}} cli this would
most likely take a lot more work than simply disabling unjar for the time being.



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