[kudu-CR] KUDU-763 consensus queue metrics on followers are messed up

["Will Berkeley (Code Review)" <ge...@cloudera.org>]

Hello Kudu Jenkins,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/3501

to look at the new patch set (#7).

Change subject: KUDU-763 consensus queue metrics on followers are messed up
......................................................................

KUDU-763 consensus queue metrics on followers are messed up

On follower tablet replicas, the majority_done_ops and
in_progress_ops metrics are wrong.

majority_done_ops = committed_index - all_replicated_opid
in_progress_ops = last_appended - committed_index

There are two reasons why:

1) followers do not update their consensus queue's committed index
2) followers do not maintain a correct value for all_replicated_opid,
since their queues generally only track the local peer and the leader
does not notify followers when ops are all-replicated.

This patch fixes 1 by having consensus notify the follower queues of
the updated committed index when the consensus committed index is
updated. This makes in_progress_ops meaningful for followers. Note
that a follower queue's committed index is not used for anything
besides the metrics.

Fixing 2 would require having the leader notify followers when
operations are all-replicated. This isn't needed for consensus, and
would be used by the followers just for the majority_done_ops metric,
so I think it's best just to zero the metric for followers and
document that it is not meaningful in that case.

Change-Id: I9fb0d45f85786b9e2631b5dc0bf044a9d3192a39
---
M src/kudu/consensus/consensus_queue-test.cc
M src/kudu/consensus/consensus_queue.cc
M src/kudu/consensus/consensus_queue.h
M src/kudu/consensus/raft_consensus.cc
4 files changed, 54 insertions(+), 9 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/01/3501/7
-- 
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I9fb0d45f85786b9e2631b5dc0bf044a9d3192a39
Gerrit-PatchSet: 7
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Will Berkeley <wd...@gmail.com>
Gerrit-Reviewer: David Ribeiro Alves <dr...@apache.org>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-Reviewer: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Will Berkeley <wd...@gmail.com>