[jira] [Commented] (MESOS-4945) Garbage collect unused docker layers in the store.

["Zhitao Li (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MESOS-4945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15586813#comment-15586813 ] 

Zhitao Li commented on MESOS-4945:
----------------------------------

Current plan:

- Add a "cleanup" method to store interface, which takes a {{vector<Image>}} for "images in use";
- store can choose its own implementation of what it wants to cleanup. Deleted images will be returned in a {{Future<vector<Image>>}};
- it's the job of Containerizer/Provisioner to actively prepare the list of "images in use"
    - initially this can simply be done by traversing all active containers, if provisioner already has all information in its memory;
- Initial implementation will add a new flag indicating upper limit of size for docker store directory, and docker::store will delete images until it drops below there;
- The invocation to store::cleanup can happen either in a background timer, upon provisioner::destroy, or before the pull? (I have no real preference, but calling it before pull seems safest if we use space based policy?);
- Initial implementation on store will traverse all images in the store;
- Further optimization including implementing a reference counting and size counting of all images in store, and checkpointing them. We might also need some kind of LRU implementation here.

> Garbage collect unused docker layers in the store.
> --------------------------------------------------
>
>                 Key: MESOS-4945
>                 URL: https://issues.apache.org/jira/browse/MESOS-4945
>             Project: Mesos
>          Issue Type: Improvement
>            Reporter: Jie Yu
>            Assignee: Zhitao Li
>
> Right now, we don't have any garbage collection in place for docker layers. It's not straightforward to implement because we don't know what container is currently using the layer. We probably need a way to track the current usage of layers.



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