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https://issues.apache.org/jira/browse/MESOS-9000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexander Rukletsov reassigned MESOS-9000:
------------------------------------------
Shepherd: Alexander Rukletsov
Assignee: Benno Evers
Sprint: Mesosphere Sprint 2018-27
Story Points: 3
Target Version/s: 1.7.0
Labels: mesosphere (was: )
Component/s: HTTP API
> Operator API event stream can miss task status updates
> ------------------------------------------------------
>
> Key: MESOS-9000
> URL: https://issues.apache.org/jira/browse/MESOS-9000
> Project: Mesos
> Issue Type: Bug
> Components: HTTP API
> Reporter: Benno Evers
> Assignee: Benno Evers
> Priority: Major
> Labels: mesosphere
>
> As of now, the master only sends TaskUpdated messages to subscribers when the
> latest known task state on the agent changed:
> {noformat}
> // src/master/master.cpp
> if (!protobuf::isTerminalState(task->state())) {
> if (status.state() != task->state()) {
> sendSubscribersUpdate = true;
> }
> task->set_state(latestState.getOrElse(status.state()));
> }
> {noformat}
> The latest state is set like this:
> {noformat}
> // src/messages/messages.proto
> message StatusUpdate {
> [...]
> // This corresponds to the latest state of the task according to the
> // agent. Note that this state might be different than the state in
> // 'status' because task status update manager queues updates. In
> // other words, 'status' corresponds to the update at top of the
> // queue and 'latest_state' corresponds to the update at bottom of
> // the queue.
> optional TaskState latest_state = 7;
> }
> {noformat}
> However, the `TaskStatus` message included in an `TaskUpdated` event is the
> event at the bottom of the queue when the update was sent.
> So we can easily get in a situation where e.g. the first TaskUpdated has
> .status.state == TASK_STARTING and .state == TASK_RUNNING, and the second
> update with .status.state == TASK_RUNNNING and .state == TASK_RUNNING would
> not get delivered because the latest known state did not change.
> This implies that schedulers can not reliably wait for the status information
> corresponding to specific task state, since there is no guarantee that
> subscribers get notified during the time when this status update will be
> included in the status field.
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