[Tarantool-patches] [PATCH 0/2] Bootstrap voter

[Vladislav Shpilevoy]

In the patch I don't like this start/stop_candidate() calls. They look bulky.
I wanted to replace them with a function like raft_try_candidate() which would
make the instance a candidate for one current term.

Also I don't like box_raft_wait_leader_found() in bootstrap. Even though it
should always succeed in a couple of WAL writes.

The only problem with having a one-term try_candidate() is the split vote in
box_promote(). There between start_candidate() and stop_candidate() several
terms can pass if they end without a leader elected. I want to keep this
working. But I couldn't find a simple way to make raft_try_candidate() work like
that.

Nor I could find a nice way to retry the candidate attempts in box_promote().
In the end, if box_raft_wait_leader_found() fails, you need to restore the
candidate state. And this leads to having some kind of start/stop_candidate
anyway.

If you have ideas how to make it look better, I am looking forward to hearing
it.

Branch: http://github.com/tarantool/tarantool/tree/gerold103/gh-6018-boot-voter
Issue: https://github.com/tarantool/tarantool/issues/6018

Vladislav Shpilevoy (2):
  replication: introduce ballot.can_be_leader
  election: during bootstrap prefer candidates

 .../unreleased/gh-6018-election-boot-voter.md |   4 +
 src/box/box.cc                                |  28 ++++-
 src/box/iproto_constants.h                    |   1 +
 src/box/replication.cc                        |  11 +-
 src/box/xrow.c                                |  14 ++-
 src/box/xrow.h                                |   2 +
 .../gh-6018-election-boot-voter.result        | 116 ++++++++++++++++++
 .../gh-6018-election-boot-voter.test.lua      |  59 +++++++++
 test/replication/gh-6018-master.lua           |  17 +++
 test/replication/gh-6018-replica.lua          |  15 +++
 test/replication/suite.cfg                    |   1 +
 11 files changed, 263 insertions(+), 5 deletions(-)
 create mode 100644 changelogs/unreleased/gh-6018-election-boot-voter.md
 create mode 100644 test/replication/gh-6018-election-boot-voter.result
 create mode 100644 test/replication/gh-6018-election-boot-voter.test.lua
 create mode 100644 test/replication/gh-6018-master.lua
 create mode 100644 test/replication/gh-6018-replica.lua

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