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haosdent commented on MESOS-3870: --------------------------------- I think ProcessManager could dequeue same Process in different work thread? {noformat} ProcessBase* ProcessManager::dequeue() { // TODO(benh): Remove a process from this thread's runq. If there // are no processes to run, and this is not a dedicated thread, then // steal one from another threads runq. ProcessBase* process = NULL; synchronized (runq_mutex) { if (!runq.empty()) { process = runq.front(); runq.pop_front(); // Increment the running count of processes in order to support // the Clock::settle() operation (this must be done atomically // with removing the process from the runq). running.fetch_add(1); } } return process; } {noformat} > Prevent out-of-order libprocess message delivery > ------------------------------------------------ > > Key: MESOS-3870 > URL: https://issues.apache.org/jira/browse/MESOS-3870 > Project: Mesos > Issue Type: Bug > Components: libprocess > Reporter: Neil Conway > Priority: Minor > Labels: mesosphere > > I was under the impression that {{send()}} provided in-order, unreliable > message delivery. So if P1 sends <M1,M2> to P2, P2 might see <>, <M1>, <M2>, > or <M1,M2> — but not <M2,M1>. > I suspect much of the code makes a similar assumption. However, it appears > that this behavior is not guaranteed. slave.cpp:2217 has the following > comment: > {noformat} > // TODO(jieyu): Here we assume that CheckpointResourcesMessages are > // ordered (i.e., slave receives them in the same order master sends > // them). This should be true in most of the cases because TCP > // enforces in order delivery per connection. However, the ordering > // is technically not guaranteed because master creates multiple > // connections to the slave in some cases (e.g., persistent socket > // to slave breaks and master uses ephemeral socket). This could > // potentially be solved by using a version number and rejecting > // stale messages according to the version number. > {noformat} > We can improve this situation by _either_: (1) fixing libprocess to guarantee > ordered message delivery, e.g., by adding a sequence number, or (2) > clarifying that ordered message delivery is not guaranteed, and ideally > providing a tool to force messages to be delivered out-of-order. -- This message was sent by Atlassian JIRA (v6.3.4#6332)