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From "Anand Mazumdar" <mazumdar.an...@gmail.com>
Subject Review Request 40660: Linked against executor PID's to ensure ordered message delivery
Date Tue, 24 Nov 2015 18:25:43 GMT

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https://reviews.apache.org/r/40660/
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Review request for mesos and Vinod Kone.


Bugs: MESOS-3851
    https://issues.apache.org/jira/browse/MESOS-3851


Repository: mesos


Description
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Previously, we did not `link` against the executor `PID` while (re)-registering. This might
lead to libprocess creating ephemeral sockets everytime a `send(...)` was invoked. This was
leading to races where messages might appear on the Executor out of order. This change does
a `link(...)` on the executor PID to ensure ordered message delivery.

---Not to be included in commit message---
I am still not comfortable bringing back the reverted commit https://reviews.apache.org/r/40107/
. I can see one more race condition even with a `link(...)`. We can still have messages coming
out of order when the first socket fails after sending the first message when still in flight.
A new socket gets created when we send the second message now, which might arrive earlier
then the first message leading to a race. But, this is a behavior that is heavily relied upon
elsewhere in our code-base. Happy to be proven wrong though and be convinced that we can bring
back the reverted commit now after this change.


Diffs
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  src/slave/slave.cpp 9055f2a789cb19f3579c15a379ea505dfef0578c 

Diff: https://reviews.apache.org/r/40660/diff/


Testing
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make check


Thanks,

Anand Mazumdar


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