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https://issues.apache.org/jira/browse/MESOS-9887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16912400#comment-16912400
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Andrei Budnik commented on MESOS-9887:
--------------------------------------
Discarding these patches ^^ since multiple consecutive requests to the
underlying containerizer might finish in a different order than they were sent.
Hence, the agent should not rely on the order of completion of requests sent to
the containerizer.
> Race condition between two terminal task status updates for Docker executor.
> ----------------------------------------------------------------------------
>
> Key: MESOS-9887
> URL: https://issues.apache.org/jira/browse/MESOS-9887
> Project: Mesos
> Issue Type: Bug
> Components: agent, containerization
> Reporter: Andrei Budnik
> Assignee: Andrei Budnik
> Priority: Blocker
> Labels: agent, containerization
> Attachments: race_example.txt
>
>
> h2. Overview
> Expected behavior:
> Task successfully finishes and sends TASK_FINISHED status update.
> Observed behavior:
> Task successfully finishes, but the agent sends TASK_FAILED with the reason
> "REASON_EXECUTOR_TERMINATED".
> In normal circumstances, Docker executor
> [sends|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/docker/executor.cpp#L758]
> final status update TASK_FINISHED to the agent, which then [gets
> processed|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5543]
> by the agent before termination of the executor's process.
> However, if the processing of the initial TASK_FINISHED gets delayed, then
> there is a chance that Docker executor terminates and the agent
> [triggers|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L6662]
> TASK_FAILED which will [be
> handled|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5816-L5826]
> prior to the TASK_FINISHED status update.
> See attached logs which contain an example of the race condition.
> h2. Reproducing bug
> 1. Add the following code:
> {code:java}
> static int c = 0;
> if (++c == 3) { // to skip TASK_STARTING and TASK_RUNNING status updates.
> ::sleep(2);
> }
> {code}
> to the
> [`ComposingContainerizerProcess::status`|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/containerizer/composing.cpp#L578]
> and to the
> [`DockerContainerizerProcess::status`|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/containerizer/docker.cpp#L2167].
> 2. Recompile mesos
> 3. Launch mesos master and agent locally
> 4. Launch a simple Docker task via `mesos-execute`:
> {code}
> # cd build
> ./src/mesos-execute --master="`hostname`:5050" --name="a"
> --containerizer=docker --docker_image=alpine --resources="cpus:1;mem:32"
> --command="ls"
> {code}
> h2. Race condition - description
> 1. Mesos agent receives TASK_FINISHED status update and then subscribes on
> [`containerizer->status()`|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5754-L5761].
> 2. `containerizer->status()` operation for TASK_FINISHED status update gets
> delayed in the composing containerizer (e.g. due to switch of the worker
> thread that executes `status` method).
> 3. Docker executor terminates and the agent
> [triggers|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L6662]
> TASK_FAILED.
> 4. Docker containerizer destroys the container. A registered callback for the
> `containerizer->wait` call in the composing containerizer dispatches [lambda
> function|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/containerizer/composing.cpp#L368-L373]
> that will clean up `containers_` map.
> 5. Composing c'zer resumes and dispatches
> `[status()|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/containerizer/composing.cpp#L579]`
> method to the Docker containerizer for TASK_FINISHED, which in turn hangs
> for a few seconds.
> 6. Corresponding `containerId` gets removed from the `containers_` map of the
> composing c'zer.
> 7. Mesos agent subscribes on
> [`containerizer->status()`|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5754-L5761]
> for the TASK_FAILED status update.
> 8. Composing c'zer returns ["Container not
> found"|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/containerizer/composing.cpp#L576]
> for TASK_FAILED.
> 9.
> `[Slave::_statusUpdate|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5826]`
> stores TASK_FAILED terminal status update in the executor's data structure.
> 10. Docker containerizer resumes and finishes processing of `status()` method
> for TASK_FINISHED. Finally, it returns control to the `Slave::_statusUpdate`
> continuation. This method
> [discovers|https://github.com/apache/mesos/blob/0026ea46dc35cbba1f442b8e425c6cbaf81ee8f8/src/slave/slave.cpp#L5808-L5814]
> that the executor has already been destroyed.
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