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https://issues.apache.org/jira/browse/YARN-7797?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16337644#comment-16337644
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Shane Kumpf commented on YARN-7797:
-----------------------------------
Thanks for the patch, [~eyang]! This will be a great feature for testing.
{quote}Does docker inspect always return the IP address right away?
{quote}
In my testing, there is a delay. I think we need to also check the container's
env and ensure that \{{YARN_CONTAINER_RUNTIME_DOCKER_CONTAINER_NETWORK}} is set
to host before we invoke the logic to set the container IP/host to the match
the NM.
{quote}My second thought is that if the IP is empty but the hostname is
populated, perhaps we should return the host address for the IP and the docker
inspect hostname for the hostname
{quote}
I believe this is the right approach, but there are caveats to this. If used
with {{RegistryDNS}}, we will have multiple hostnames returned in the PTR
lookup, which can lead to non-deterministic behavior. If the NM is restarted,
and the NM host is using {{RegistryDNS}} as its resolver, the NM may report in
to the RM with our container hostname. Also, if no hostname is supplied, I've
regularly seen _localhost_ and _localhost.localdomain_ as the container
hostname, and I don't think creating entries in {{RegistryDNS}} would be
appropriate for those hostnames. Perhaps it would be good to return the NM
hostname in that case? Despite the caveats, using the container hostname allows
us to validate DNS and forward lookups will work for containers, which is very
valuable in testing, so I do think we should use the container hostname where
possible.
Given the potential issues, perhaps it would be good to add a small warning to
the docs that _--net=host_ is really only appropriate for testing and/or
administrators that understand the implications of enabling it?
> Docker host network can not obtain IP address for RegistryDNS
> -------------------------------------------------------------
>
> Key: YARN-7797
> URL: https://issues.apache.org/jira/browse/YARN-7797
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: nodemanager
> Affects Versions: 3.1.0
> Reporter: Eric Yang
> Assignee: Eric Yang
> Priority: Major
> Attachments: YARN-7797.001.patch
>
>
> When docker is configured to use host network, docker inspect command does
> not return IP address of the container. This prevents IP information to be
> collected for RegistryDNS to register a hostname entry for the docker
> container.
> The proposed solution is to intelligently detect the docker network
> deployment method, and report back host IP address for RegistryDNS.
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