[jira] [Updated] (MESOS-4658) process::Connection can lead to deadlock around execution in the same context.

["Anand Mazumdar (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MESOS-4658?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Anand Mazumdar updated MESOS-4658:
----------------------------------
    Shepherd: Benjamin Mahler

> process::Connection can lead to deadlock around execution in the same context.
> ------------------------------------------------------------------------------
>
>                 Key: MESOS-4658
>                 URL: https://issues.apache.org/jira/browse/MESOS-4658
>             Project: Mesos
>          Issue Type: Bug
>          Components: HTTP API, libprocess
>            Reporter: Anand Mazumdar
>            Assignee: Shuai Lin
>              Labels: mesosphere
>
> The {{Connection}} abstraction is prone to deadlocks arising from the object being destroyed inside the same execution context.
> Consider this example:
> {code}
> Option<Connection> connection = process::http::connect(...).get();
> connection.disconnected()
>   .onAny(defer(self(), &SomeFunc, connection));
> connection.disconnect();
> connection = None();
> {code}
> In the above snippet, if the {{connection = None()}} gets executed first before the actual dispatch to {{ConnectionProcess}} happens. You might loose the only existing reference to {{Connection}} object inside {{ConnectionProcess::disconnect}}. This would lead to the destruction of the {{Connection}} object in the {{ConnectionProcess}} execution context.
> We do have a snippet in our existing code that alludes to such occurrences happening: 
> https://github.com/apache/mesos/blob/master/3rdparty/libprocess/src/http.cpp#L1325
> {code}
>   // This is a one time request which will close the connection when
>   // the response is received. Since 'Connection' is reference-counted,
>   // we must keep a copy around until the disconnection occurs. Note
>   // that in order to avoid a deadlock (Connection destruction occurring
>   // from the ConnectionProcess execution context), we use 'async'.
> {code}
> AFAICT, for scenarios where we need to hold on to the {{Connection}} object for later, this approach does not suffice.



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