[Tarantool-patches] [PATCH v4 0/2] relay: provide downstream lag information

[Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Guys, take a look once time permit. Previous version is here
https://lists.tarantool.org/tarantool-patches/20210430153940.121271-1-gorcunov@gmail.com/

v4 (by Vlad):
 - add a test case
 - add docbot request
 - dropped off xrow_encode_vclock_timed, we use opencoded assignment
   for tm value when send ack
 - struct awstat renamed to applier_wal_stat. Vlad I think this is
   better name than "applier_lag" because this is statistics on WAL,
   we simply track remote WAL propagation here, so more general name
   is better for grep sake and for future extensions
 - instead of passing applier structure we pass replica_id
 - the real keeper of this statistics comes into "replica" structure
   thus unbound of applier itself
 - for synchro entries we pass a pointer to the applier_wal_stat instead
   of using replica_id = 0 as a sign that we don't need to update statistics
   for initial and final join cases
 - to write and read statistics we provide wal_stat_update and wal_stat_ack
   helpers to cover the case where single ACK spans several transactions

branch: gorcunov/gh-5447-relay-lag-4
issue: https://github.com/tarantool/tarantool/issues/5447

Cyrill Gorcunov (2):
  applier: send transaction's first row WAL time in the applier_writer_f
  relay: provide information about downstream lag

 .../unreleased/gh-5447-downstream-lag.md      |  6 ++
 src/box/applier.cc                            | 92 +++++++++++++++---
 src/box/applier.h                             | 14 +++
 src/box/lua/info.c                            |  3 +
 src/box/relay.cc                              | 18 ++++
 src/box/relay.h                               |  6 ++
 src/box/replication.cc                        |  3 +
 src/box/replication.h                         |  4 +
 .../replication/gh-5447-downstream-lag.result | 93 +++++++++++++++++++
 .../gh-5447-downstream-lag.test.lua           | 41 ++++++++
 10 files changed, 267 insertions(+), 13 deletions(-)
 create mode 100644 changelogs/unreleased/gh-5447-downstream-lag.md
 create mode 100644 test/replication/gh-5447-downstream-lag.result
 create mode 100644 test/replication/gh-5447-downstream-lag.test.lua


base-commit: 4500547d7a177c0b49bff35c922286b4f21c8719
-- 
2.30.2