Lars Volker has uploaded a new patch set (#2). Change subject: IMPALA-3019: Fix unnecessary resets of iterator ......................................................................
IMPALA-3019: Fix unnecessary resets of iterator In order to perform round-robin backend selection, the simple scheduler uses an iterator to the next backend entry to be selected. This iterator needs to be reset whenever it is invalidated by changes to the underlying map. The current behavior resets the pointer on every message of the statestored, even if the message was empty and thus did not result in any changes to the map. After every reset of the iterator round-robin selection starts from the first backend in the scheduler's backend map. As the statestored sends empty keepalive messages every couple of seconds, this effectively limits scheduling of remote reads to only a few backends. This change introduces a check to prevent those unnecessary iterator resets, which will spread remote reads more evenly over all backends. Change-Id: I831d485b46c7d9460fb014a302a26864b6bd573e Reviewed-on: http://gerrit.cloudera.org:8080/2330 Reviewed-by: Lars Volker <[email protected]> Tested-by: Internal Jenkins (cherry picked from commit fc743d69f8ed671cebaca89f41f5373e326ffee5) --- M be/src/scheduling/simple-scheduler.cc 1 file changed, 6 insertions(+), 1 deletion(-) git pull ssh://gerrit.cloudera.org:29418/Impala refs/changes/31/3031/2 -- To view, visit http://gerrit.cloudera.org:8080/3031 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: newpatchset Gerrit-Change-Id: I831d485b46c7d9460fb014a302a26864b6bd573e Gerrit-PatchSet: 2 Gerrit-Project: Impala Gerrit-Branch: cdh5-trunk Gerrit-Owner: Lars Volker <[email protected]> Gerrit-Reviewer: Internal Jenkins
