[tarantool-patches] [PATCH v2 0/2] SWIM log TTD, and TTL

[Vladislav Shpilevoy]

It is a first patchset to make SWIM more usable in big clusters. Most of the
problems arise from incorrect interpretation of the original SWIM paper, and
extensions adaptation.

The first commit makes SWIM conform with the original paper and disseminate
each event for log(cluster_size) times instead of cluster_size. After it there
appears a problem in too early deletion of dead and left members, when GC is on.
Strictly speaking, it existed even before the patch, but now it is more clear.

The second commit tries to solve it by keeping dead and left members in a limbo
queue until the whole cluster is aware about their death. It solves the problem
partially, but doesn't work when heartbeat_rate is too small. See the commit
message for an explanation.

However, there is another solution how to do not struggle with TTL and limbo.
I've sent it in another thread.

V1: https://www.freelists.org/post/tarantool-patches/PATCH-02-SWIM-big-cluster-improvements-part-1
Changes in V2:
- Drop commit about preference of new events over old ones;
- Split logarithmic TTD and TTL + limbo queue in separate commits;

Branch: http://github.com/tarantool/tarantool/tree/gerold103/gh-4253-dissemination-speed
Issue: https://github.com/tarantool/tarantool/issues/4253

Vladislav Shpilevoy (2):
  swim: disseminate event for log(cluster_size) steps
  [RAW] swim: send 'left' and 'dead' to limbo before deletion

 src/lib/swim/swim.c   | 117 ++++++++++++++++++++++++++++++++++++++++--
 test/unit/swim.c      |  74 ++++++++++++++++++++++++--
 test/unit/swim.result |   8 ++-
 3 files changed, 190 insertions(+), 9 deletions(-)

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