From: Kirill Yukhin <kyukhin@tarantool.org> To: tarantool-patches@freelists.org Subject: [tarantool-patches] [sergepetrenko@tarantool.org: [server-dev] [PATCH] replication: disallow bootstrap of read-only masters] Date: Thu, 12 Sep 2019 07:54:29 +0300 [thread overview] Message-ID: <20190912045429.kv7cs54od52gbklb@tarantool.org> (raw) Hello, ----- Forwarded message from Serge Petrenko <sergepetrenko@tarantool.org> ----- Date: Tue, 3 Sep 2019 20:06:41 +0300 From: Serge Petrenko <sergepetrenko@tarantool.org> To: georgy@tarantool.org Cc: server-dev@tarantool.org, Serge Petrenko <sergepetrenko@tarantool.org> Subject: [server-dev] [PATCH] replication: disallow bootstrap of read-only masters X-Mailer: git-send-email 2.20.1 (Apple Git-117) In a configuration with several read-only and read-write instances, if replication_connect_quorum is not greater than the amount of read-only instances and replication_connect_timeout happens to be small enough for some read-only instances to form a quorum and exceed the timeout before any of the read-write instaces start, all these read-only instances will choose themselves a read-only bootstrap leader. This 'leader' will successfully bootstrap itself, but will fail to register any of the other instances in _cluster table, since it isn't writeable. As a result, some of the read-only instances will just die unable to bootstrap from a read-only bootstrap leader, and when the read-write instances are finally up, they'll see a single read-only instance which managed to bootstrap itself and now gets a REPLICASET_UUID_MISMATCH error, since no read-write instance will choose it as bootstrap leader, and will rather bootstrap from one of its read-write mates. The described situation is clearly not what user has hoped for, so throw an error, when a read-only instance tries to initiate the bootstrap. The error will give the user a cue that he should increase replication_connect_timeout. Closes #4321 This patch was reviewed during ML downtime. Checked in to 1.10, 2.1, 2.2 and master. -- Regards, Kirill Yukhin
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