Neil Conway created MESOS-3870: ---------------------------------- Summary: 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
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)