Re: [Tarantool-patches] [PATCH v9 1/2] applier: send transaction's first row WAL time in the applier_writer_f

[Serge Petrenko via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

18.06.2021 21:06, Cyrill Gorcunov пишет:
> Serge, I've update the patch and force pushed it, please take a look.

Thanks for the fixes!
LGTM.
> ---
> From: Cyrill Gorcunov <gorcunov@gmail.com>
> Subject: [PATCH] relay: provide information about downstream lag
>
> We already have `box.replication.upstream.lag` entry for monitoring
> sake. Same time in synchronous replication timeouts are key properties
> for quorum gathering procedure. Thus we would like to know how long
> it took of a transaction to traverse `initiator WAL -> network ->
> remote applier -> initiator ACK reception` path.
>
> Typical output is
>
>   | tarantool> box.info.replication[2].downstream
>   | ---
>   | - status: follow
>   |   idle: 0.61753897101153
>   |   vclock: {1: 147}
>   |   lag: 0
>   | ...
>   | tarantool> box.space.sync:insert{69}
>   | ---
>   | - [69]
>   | ...
>   |
>   | tarantool> box.info.replication[2].downstream
>   | ---
>   | - status: follow
>   |   idle: 0.75324084801832
>   |   vclock: {1: 151}
>   |   lag: 0.0011014938354492
>   | ...
>
> Closes #5447
>
> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
>
> @TarantoolBot document
> Title: Add `box.info.replication[n].downstream.lag` entry
>
> `replication[n].downstream.lag` represents a lag between the main
> node writes a certain transaction to it's own WAL and a moment it
> receives an ack for this transaction from a replica.
> ---
>

-- 
Serge Petrenko