[Tarantool-patches] [PATCH v2 0/4] Boot with anon

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

The patch attempts to address with problem of anonymous replicas being
registered in _cluster, if they are present during bootstrap.

The bug was found during working on another issue related to Raft. The problem
is that Raft won't work properly during bootstrap if non-joined replicas are
registered in _cluster.

When their auto-registration by applier was removed, the anon bug was found.

The auto-registration removal is trivial, but it breaks the cluster bootstrap in
another way creating false-positive XlogGap errors. See the second commit with
an explanation. To solve the issue quite a radical solution is applied - gap
errors are not considered critical anymore, and can be retried. I am not sure
that is the best option, but couldn't come up with anything better after a long
struggle with that.

This is a bug, so whatever we will come up with after all, it should be pushed
to the older versions too.

Branch: http://github.com/tarantool/tarantool/tree/gerold103/gh-5287-anon-false-register
Issue: https://github.com/tarantool/tarantool/issues/5287

Changes in v2:
- Anon status is stored as a flag again. In v1 it was stored as enum, but an
  alternative solution was proposed, where the enum is not needed.
- Ballot now has a new field is_anon. It helps to avoid the enum, and set
  replica->anon flag to a correct value right when it becomes connected. Through
  relay or applier, either.

@ChangeLog
* Anonymous replica could be registered and could prevent WAL files removal (gh-5287).
* XlogGapError is not a critical error anymore. It means, box.info.replication will show upstream status as 'loading' if the error was found. The upstream will be restarted until the error is resolved automatically with a help of another instance, or until the replica is removed from box.cfg.replication (gh-5287).

Vladislav Shpilevoy (4):
  xlog: introduce an error code for XlogGapError
  replication: retry in case of XlogGapError
  replication: add is_anon flag to ballot
  replication: do not register outgoing connections

 src/box/applier.cc                            |  40 ++++
 src/box/box.cc                                |  30 +--
 src/box/errcode.h                             |   2 +
 src/box/error.cc                              |   2 +
 src/box/error.h                               |   1 +
 src/box/iproto_constants.h                    |   1 +
 src/box/recovery.h                            |   2 -
 src/box/replication.cc                        |  14 +-
 src/box/xrow.c                                |  14 +-
 src/box/xrow.h                                |   5 +
 test/box/error.result                         |   2 +
 test/replication/autobootstrap_anon.lua       |  25 +++
 test/replication/autobootstrap_anon1.lua      |   1 +
 test/replication/autobootstrap_anon2.lua      |   1 +
 test/replication/force_recovery.result        | 110 -----------
 test/replication/force_recovery.test.lua      |  43 -----
 test/replication/gh-5287-boot-anon.result     |  81 +++++++++
 test/replication/gh-5287-boot-anon.test.lua   |  30 +++
 test/replication/prune.result                 |  18 +-
 test/replication/prune.test.lua               |   7 +-
 test/replication/replica.lua                  |   2 +
 test/replication/replica_rejoin.result        |   6 +-
 test/replication/replica_rejoin.test.lua      |   4 +-
 .../show_error_on_disconnect.result           |   2 +-
 .../show_error_on_disconnect.test.lua         |   2 +-
 test/xlog/panic_on_wal_error.result           | 171 ------------------
 test/xlog/panic_on_wal_error.test.lua         |  75 --------
 27 files changed, 262 insertions(+), 429 deletions(-)
 create mode 100644 test/replication/autobootstrap_anon.lua
 create mode 120000 test/replication/autobootstrap_anon1.lua
 create mode 120000 test/replication/autobootstrap_anon2.lua
 delete mode 100644 test/replication/force_recovery.result
 delete mode 100644 test/replication/force_recovery.test.lua
 create mode 100644 test/replication/gh-5287-boot-anon.result
 create mode 100644 test/replication/gh-5287-boot-anon.test.lua
 delete mode 100644 test/xlog/panic_on_wal_error.result
 delete mode 100644 test/xlog/panic_on_wal_error.test.lua

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