Hello Fengling Wang, Tidy Bot, Mike Percy, Alexey Serbin,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/11251
to look at the new patch set (#18).
Change subject: KUDU-2245 Graceful leadership transfer
......................................................................
KUDU-2245 Graceful leadership transfer
This patch implements graceful leadership transfer, as described in the
original Raft thesis. It has the following steps:
1. An admin client sends a request to the tablet leader for it to
transfer leadership. The client can indicate a specific voter that it
wants to become the leader, or it can allow the current leader to
choose its successor.
2. The leader receives the request and begins a leader transfer period.
During a leader transfer period, the leader does not accept writes or
config change requests. This allows followers to catch up to the
leader. A background timer expires the transfer period after one
election timeout, since clients should be able to ride over
interruptions in service lasting at least that long. If another
request to transfer leadership is received during a transfer period,
it will be rejected.
3. During the transfer period, the leader continues to update peers.
When it receives a response from a peer, it checks if that peer is
a voter and fully caught up to the leader's log. If it is, and if it
is the designated successor if one was provided, the leader signals
the peer to start an election, which it should win. If no eligible
successor appears, the transfer period expires and the leader resumes
normal operation.
This is an improvement over the current leader step down method, which
causes the leader to simply relinquish leadership and snooze its
election timer for an extra long period, so another voter will likely
become leader. Leadership transfer should usually be much faster and it
allows the client to select the new leader among current voters.
However, note that it does not provide strictly better guarantees- it is
still possible that leadership will not be transferred.
I ran TestRepeatLeaderStepDown and TestGracefulLeaderStepDown 1000 times
and 200 times each, in debug and TSAN modes, with 4 stress threads, and
saw no failures.
Change-Id: Ic97343af9eb349556424c999799ed5e2941f0083
---
M src/kudu/consensus/consensus-test-util.h
M src/kudu/consensus/consensus.proto
M src/kudu/consensus/consensus_peers.cc
M src/kudu/consensus/consensus_peers.h
M src/kudu/consensus/consensus_queue.cc
M src/kudu/consensus/consensus_queue.h
M src/kudu/consensus/peer_manager.cc
M src/kudu/consensus/peer_manager.h
M src/kudu/consensus/raft_consensus.cc
M src/kudu/consensus/raft_consensus.h
M src/kudu/integration-tests/raft_consensus-itest.cc
M src/kudu/tools/kudu-admin-test.cc
M src/kudu/tools/kudu-tool-test.cc
M src/kudu/tools/tool_action_tablet.cc
M src/kudu/tools/tool_replica_util.cc
M src/kudu/tools/tool_replica_util.h
M src/kudu/tserver/tablet_service.cc
17 files changed, 839 insertions(+), 67 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/51/11251/18
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ic97343af9eb349556424c999799ed5e2941f0083
Gerrit-Change-Number: 11251
Gerrit-PatchSet: 18
Gerrit-Owner: Will Berkeley <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Fengling Wang <[email protected]>
Gerrit-Reviewer: Mike Percy <[email protected]>
Gerrit-Reviewer: Tidy Bot
Gerrit-Reviewer: Will Berkeley <[email protected]>
