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https://issues.apache.org/jira/browse/MESOS-3785?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Till Toenshoff updated MESOS-3785:
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Target Version/s: 0.27.0 (was: 0.26.0)
> Use URI content modification time to trigger fetcher cache updates.
> -------------------------------------------------------------------
>
> Key: MESOS-3785
> URL: https://issues.apache.org/jira/browse/MESOS-3785
> Project: Mesos
> Issue Type: Improvement
> Components: fetcher
> Reporter: Bernd Mathiske
> Assignee: Benjamin Bannier
> Labels: mesosphere
>
> Instead of using checksums to trigger fetcher cache updates, we can for
> starters use the content modification time (mtime), which is available for a
> number of download protocols, e.g. HTTP and HDFS.
> Proposal: Instead of just fetching the content size, we fetch both size and
> mtime together. As before, if there is no size, then caching fails and we
> fall back on direct downloading to the sandbox.
> Assuming a size is given, we compare the mtime from the fetch URI with the
> mtime known to the cache. If it differs, we update the cache. (As a defensive
> measure, a difference in size should also trigger an update.)
> Not having an mtime available at the fetch URI is simply treated as a unique
> valid mtime value that differs from all others. This means that when
> initially there is no mtime, cache content remains valid until there is one.
> Thereafter, anew lack of an mtime invalidates the cache once. In other
> words: any change from no mtime to having one or back is the same as
> encountering a new mtime.
> Note that this scheme does not require any new protobuf fields.
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