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From "Craig Macdonald (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2857) libhdfs: no way to set JVM args other than classpath
Date Sat, 23 Feb 2008 01:39:19 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2857?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12571678#action_12571678
] 

Craig Macdonald commented on HADOOP-2857:
-----------------------------------------

I'm quite happy to rename the variable. To HADOOP_OPTS would make most sense to me, as the
options that  can be set (any JVM args including System properties etc, memory consumption,
etc), are exactly the same as someone might set for Hadoop, so why should it be any different
to HADOOP_OPTS? A user of a C application that uses libhdfs might not know that it's libhdfs
that the C application uses, but rather just Hadoop in general, so HADOOP_OPTS might be better
than LIBHDFS_OPTS. However, I'm happy to take arguments either way.  

Make the call on the env vaar name, and can anyone provide feedback - I'm not a natural C
coder. Should I be using strtok_r instead of strtok? Do I need to do the tokenisation twice?

> libhdfs: no way to set JVM args other than classpath
> ----------------------------------------------------
>
>                 Key: HADOOP-2857
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2857
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: libhdfs
>    Affects Versions: 0.16.0
>            Reporter: Craig Macdonald
>            Priority: Minor
>         Attachments: patch.libhdfs.jvm.args
>
>   Original Estimate: 5h
>  Remaining Estimate: 5h
>
> I would like a way to set other Java system properties and/or other Java VM arguments
when using libhdfs - i.e. I want to be able to say start a profiler, attach a debugger, or
increase the memory available to the VM.
> At present, new JVMs are initialised from the getJNIEnv(void) method in src/c++/libhdfs/hdfsJniHelper.c
> This method initialises the -Djava.class.path JVM argument from the CLASSPATH environment
variable. I am proposing that another env variable should be added, the contents of which
is passed (almost) verbatim as JVM arguments.
> Eg, say the env var JVM_ARGS is used. The string from the env var would be tokenised
on "one or more spaces", and would be passed as additional JVM arguments, by make a larger
JavaVMOption options[] array, and setting vm_args.nOptions = 1+ number of passed arguments.
> Only flaw I can see with this is that none of the passed parameters can contain spaces.

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