James Peach created MESOS-9172:
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Summary: Fetcher deadlock with duplicated URIs.
Key: MESOS-9172
URL: https://issues.apache.org/jira/browse/MESOS-9172
Project: Mesos
Issue Type: Bug
Components: fetcher
Reporter: James Peach
Assignee: James Peach
If the fetcher cache is empty and you launch a task that contains duplicate
URIs, the fetcher deadlocks waiting for the futures in
{{FetcherProcess::_fetch}}.
What happens is that when the fetcher is setting up the initial match of cache
lookup futures in {{FetcherProcess::fetch}}, the duplicate URIs cause cache
hits on the placeholder cache entries. This code is assuming that there is
already an operation in flight that will populate the cache entry. However, the
cache is currently empty - the placeholder entry is caused by a the duplicate
in the task's URIs.
When we await the futures in {{FetcherProcess::_fetch}}, we end up waiting for
the future that indicated the cache entry becomes populated, but that won't
ever happen because we need to make progress on the current fetching batch in
order to populate the cache entry. At this point we are live-locked.
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