[jira] [Created] (MESOS-5332) TASK_LOST on slave restart potentially due to executor race condition

["Stephan Erb (JIRA)" <ji...@apache.org>]

Stephan Erb created MESOS-5332:
----------------------------------

             Summary: TASK_LOST on slave restart potentially due to executor race condition
                 Key: MESOS-5332
                 URL: https://issues.apache.org/jira/browse/MESOS-5332
             Project: Mesos
          Issue Type: Bug
          Components: libprocess, slave
    Affects Versions: 0.26.0
         Environment: Mesos 0.26
Aurora 0.13
            Reporter: Stephan Erb


When restarting the Mesos agent binary, tasks can end up as LOST. We lose from 20% to 50% of all tasks. They are killed by the Mesos agent via:

{code}
I0505 08:42:06.781318 21738 slave.cpp:2702] Cleaning up un-reregistered executors
I0505 08:42:06.781366 21738 slave.cpp:2720] Killing un-reregistered executor 'thermos-nobody-devel-service-28854-0-6a88d62e-656
4-4e33-b0bb-1d8039d97afc' of framework 20151001-085346-58917130-5050-37976-0000 at executor(1)@10.X.X.X:40541
I0505 08:42:06.781446 21738 slave.cpp:2720] Killing un-reregistered executor 'thermos-nobody-devel-service-23839-0-1d2cd0e6-699
4-4cba-a9df-3dfc1552667f' of framework 20151001-085346-58917130-5050-37976-0000 at executor(1)@10.X.X.X:35757
I0505 08:42:06.781466 21738 slave.cpp:2720] Killing un-reregistered executor 'thermos-nobody-devel-service-29970-0-478a7291-d070-4aa8
-af21-6fda889f750c' of framework 20151001-085346-58917130-5050-37976-0000 at executor(1)@10.X.X.X:51463
...
I0505 08:42:06.781558 21738 slave.cpp:4230] Finished recovery
{code}


We have verified that the tasks and their executors are killed by the agent during startup. When stopping the agent using supervisorctl stop, the executors are still running (verified via {{ps aux}}). They are only killed once the agent tries to reregister.

The issue is hard to reproduce:

* When restarting the agent binary multiple times, tasks are only lost for the first restart.
* It is much more likely to occur if the agent binary has been running for a longer period of time (> 7 days)
* It tends to be more likely if the host has many cores (30-40) and thus many libprocess workers. 


Mesos is correctly sticking to the 2 seconds wait time before killing un-reregistered executors. The failed executors receive the reregistration request, but it seems like they fail to send a reply.

A successful reregistration:
{code}
I0505 08:41:59.581231 21664 exec.cpp:456] Slave exited, but framework has checkpointing enabled. Waiting 15mins to reconnect with slave 20160118-141153-92471562-5050-6270-S17
I0505 08:42:04.780591 21665 exec.cpp:256] Received reconnect request from slave 20160118-141153-92471562-5050-6270-S17
I0505 08:42:04.785297 21676 exec.cpp:233] Executor re-registered on slave 20160118-141153-92471562-5050-6270-S17
I0505 08:42:04.788579 21676 exec.cpp:245] Executor::reregistered took 1.492339ms
{code}

A failed one:
{code}
I0505 08:42:04.779677  2389 exec.cpp:256] Received reconnect request from slave 20160118-141153-92471562-5050-6270-S17
E0505 08:42:05.481374  2408 process.cpp:1911] Failed to shutdown socket with fd 11: Transport endpoint is not connected
I0505 08:42:05.481374  2395 exec.cpp:456] Slave exited, but framework has checkpointing enabled. Waiting 15mins to reconnect with slave 20160118-141153-92471562-5050-6270-S17
{code}

All task ending up in LOST have an output similar to the one posted above, i.e. messages seem to be received in a wrong order.

Anyone an idea what might be going on here? 



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