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From: Konstantin Osipov <kostja.osipov@gmail.com>
To: Olga Arkhangelskaia <arkholga@tarantool.org>
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH rfc 0/1] replication: stop resetting existing connections
Date: Thu, 2 Apr 2020 19:43:11 +0300	[thread overview]
Message-ID: <20200402164311.GA9239@atlas> (raw)
In-Reply-To: <1d29a21b-78bd-d3a8-0210-fb8f9690aea4@tarantool.org>

* Olga Arkhangelskaia <arkholga@tarantool.org> [20/04/02 19:07]:
> 02.04.2020 16:47, Konstantin Osipov пишет:
> > * Olga Arkhangelskaia <arkholga@tarantool.org> [20/04/02 16:30]:
> > 
> > Could you please explain the idea of the patch?
> > 
> > As far I can see, you do some strcmp magic to understand if the
> > uri is the same.
> Yes.
> > 
> > Why not use instance uuids?
> 
> I did not think of uuids in such a way. But  after reading your description
> it
> 
> seems good idea (As I understand  even if we have 3301 and localhost:3301
> they will have the same uuid).
> 
> But I am not sure about appliers that should be removed.
> 
> If there is no UUIDS of existing applier in new appliers pool it should be
> removed?
> 
> And we still need to do all this work even if we just changed order in the
> config.

We could perhaps optimize things based on some heuristics, like
old and new uri match 100%, but first we need to settle on the
main algorithm. 

E.g. one variation could be that, given appliers are ref-counted,
we do not create a new applier for a 100% match, but simply add it
directly to the new uuid -> applier hash. 

Please suggest an edit to this:
> 
> > 0) Introduce uuid -> applier hash.
> > 1) Create new appliers for all entries in replication.
> > 2) Establish connections, but do not issue SUBSCRIBE yet.
> > 3) Look at connection server uuids. If this uuid is already
> >     connected to, then (easy) quietly close the new connection,
> >     and add existing connection to the new instance of uuid hash.
> > 4) Add the new connection to the new instance of uuid hash.
> > If there is a duplicate in the *new* instance of the uuid hash,
> > produce "duplicate connection" error. Otherwise remove/delete all
> > appliers that are left in the old uuid hash.
> > 
> > Perhaps we need applier reference counting to make this work
> > smoothly

-- 
Konstantin Osipov, Moscow, Russia

      reply	other threads:[~2020-04-02 16:43 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-02 13:29 Olga Arkhangelskaia
2020-04-02 13:29 ` [Tarantool-patches] [PATCH rfc 1/1] " Olga Arkhangelskaia
2020-04-02 13:47 ` [Tarantool-patches] [PATCH rfc 0/1] " Konstantin Osipov
2020-04-02 16:05   ` Olga Arkhangelskaia
2020-04-02 16:43     ` Konstantin Osipov [this message]

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