[Tarantool-patches] [PATCH] applier: fix upstream.lag calculations

[Vitaliia Ioffe]

Hi Sergey, 
 
I’m so sorry for saying it: but this fix is not a fix. I have to underline there were failed tests:
[037] replication/errinj.test.lua                     memtx           [ fail ]
[037] replication/errinj.test.lua                     vinyl              [ fail ]
 
You can find it here: 
https://github.com/tarantool/tarantool/runs/3322606890
 
 
--
Vitaliia Ioffe
 
  
>Пятница, 13 августа 2021, 17:25 +03:00 от Serge Petrenko <sergepetrenko at tarantool.org>:
> 
>upstream.lag is the delta between the moment when a row was written to
>master's journal and the moment when it was received by the replica.
>It's an important metric to check whether the replica has fallen too far
>behind master.
>
>Not all the rows coming from master have a valid time of creation. For
>example, RAFT system messages don't have one, and we can't assign
>correct time to them: these messages do not originate from the journal,
>and assigning current time to them would lead to jumps in upstream.lag
>results.
>
>Stop updating upstream.lag for rows which don't have creation time
>assigned.
>
>This also fixes the flaky replication/errinj.test.lua
>---
>https://github.com/tarantool/tarantool/tree/sp/applier-lag-fix
>
> src/box/applier.cc | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/src/box/applier.cc b/src/box/applier.cc
>index 902d0bc72..9256078e1 100644
>--- a/src/box/applier.cc
>+++ b/src/box/applier.cc
>@@ -664,7 +664,8 @@ applier_read_tx_row(struct applier *applier, double timeout)
> 
>  coio_read_xrow_timeout_xc(coio, ibuf, row, timeout);
> 
>- applier->lag = ev_now(loop()) - row->tm;
>+ if (row->tm > 0)
>+ applier->lag = ev_now(loop()) - row->tm;
>  applier->last_row_time = ev_monotonic_now(loop());
>  return tx_row;
> }
>--
>2.30.1 (Apple Git-130)
 
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