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https://issues.apache.org/jira/browse/YARN-5621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15507320#comment-15507320
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Chris Douglas commented on YARN-5621:
-------------------------------------
I think I see where the CL proposal was unclear.
It is an alternative to CE changes; container start remains as-is. The proposal
was scoped only to localizing resources for running containers. The CE is
agnostic to new/running containers for an application- it may be used by both,
concurrently. By adding a new command {{LINK}} to its protocol, the NM can
instruct the {{ContainerLocalizer}} to create a symlink to a resource for a
running container. Again, these commands could be grouped.
{quote}
> a case that already exists for containers on the same node requesting the
> same resource
Do you mean this is an existing implemented functionality or this is an
existing use-case?
{quote}
Neither. The case where running containers (c ~1x~, c ~2y~) for different
applications (a ~1~, a ~2~) request the same resource _R_ exists. Both will
start {{ContainerLocalizer}} instances, but only one will download the resource
to the private cache. In the CL proposal, this is the same as rollback, where
the CL starts, heartbeats, then receives a command to LINK an existing resource
without downloading anything. By "a case that already exists", I meant it's a
case the CL proposal handles implicitly.
bq. yeah, I feel it's inefficient to start a localizer process to only create
symlinks..
No question. But if localizing a new resource takes a few seconds, for services
that upgrade over minutes/hours, then a few hundred milliseconds is not worth
adding {{RUN_SCRIPT}} to the CE.
> Support LinuxContainerExecutor to create symlinks for continuously localized
> resources
> --------------------------------------------------------------------------------------
>
> Key: YARN-5621
> URL: https://issues.apache.org/jira/browse/YARN-5621
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Jian He
> Assignee: Jian He
> Attachments: YARN-5621.1.patch, YARN-5621.2.patch, YARN-5621.3.patch,
> YARN-5621.4.patch, YARN-5621.5.patch
>
>
> When new resources are localized, new symlink needs to be created for the
> localized resource. This is the change for the LinuxContainerExecutor to
> create the symlinks.
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