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https://issues.apache.org/jira/browse/HADOOP-16312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16838676#comment-16838676
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Eric Yang commented on HADOOP-16312:
------------------------------------
{quote}Would you be so kind Eric Yang to explain it more details? Can you
please give me an example how scm process is respawned in the ozone compose
clusters (where hadoop-runner is used together with dumb-init).{quote}
That statement is flawed. It does not respawn the program. Instead, i meant
reparenting orphaned child processes and keep them alive or reap them. It is
possible to use:
{code}
CMD ["/bin/bash", "-c", "set -e && /opt/apache/ozone/bin/ozone"]
{code}
to accomplish the same. Kill the container will result in SIGKILL on orphaned
child processes to get a cleaner system. We can talk about if it is ok to kill
Ozone threads with SIGKILL with some clean up strategy for empty or corrupted
files or we want to code logic into signal handling for Ozone threads. I don't
think we can do much to manage some JVM native threads, and the current
starter.sh will result in process threads that look like this:
{code}
/dumb-init
+--- /usr/bin/dumb-init
+--- /bin/bash
+--- java ...
{code}
Bash will not forward signal handling to Java. Instead, the proper usage is:
{code}
exec java ...
{code}
The process tree will look like:
{code}
/dumb-init
+--- java ...
{code}
This will ensure the signal handling is correct.
> Remove dumb-init from hadoop-runner image
> -----------------------------------------
>
> Key: HADOOP-16312
> URL: https://issues.apache.org/jira/browse/HADOOP-16312
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Elek, Marton
> Priority: Major
>
> This issue is reported by [~eyang] in HDDS-1495.
> I think it's better to discuss under a separated issue as it's unrelated to
> HDDS-1495.
> The original problem description from [~eyang]
> {quote}Dumb-init is one way to always run contaized program in the
> background and respawn the program when program fails. This is poor man’s
> solution for keeping program alive.
> Cluster management software like Kubernetes or YARN have additional policy
> and logic to start the same docker container on a different node. Therefore,
> Dumb-init is not recommended for future Hadoop daemons instead allow cluster
> management software to make decision where to start the container. Dumb-init
> for demonize docker container will be removed, and change to use
> entrypoint.sh Docker provides -d flag to demonize foreground process. Most of
> the management system built on top of Docker, (ie. Kitematic, Apache YARN,
> and Kubernetes) integrates with Docker container at foreground to aggregate
> stdout and stderr output of the containerized program.
> {quote}
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