tarantool / tarantool / 25000294112

86%

master: 88%

Build Type

push

github

Committed by sergepetrenko

Commit Message

txn: forbid waiting for acks on fully local transactions

We recommend making all spaces synchronous (including the system ones)
whenever the user has at least one of them. However, once `_truncate`
becomes synchronous, it is impossible to truncate any local space,
either on the master or on a replica. On master the truncate succeeds,
however recovering from such xlogs produces "Tarantool does not support
Non-blocking commit of a synchronous txn" error and replica disconnects
from the master with SplitBrain: "got a request mentioning future lsn".
On replica the truncate hangs (in case of Debug build the assertion for
non-ro limbo fails).

The `_truncate` space itself is unusual: it marks rows related to local
spaces as GROUP_LOCAL (they are not replicated), while all other rows
remain GROUP_GLOBAL. As a result, when we truncate a local space all rows
in the transaction are local, and we add such transaction to limbo. If
truncate of local space happens on master, the transaction is confirmed
and since replica doesn't have it, SplitBrain occurs. On replica such
truncate cannot be confirmed, since replica is not an owner of the
limbo.

We should not mark such transactions as synchronous. Instead, it should
follow the asynchronous transaction path: add them to limbo iff it's not
empty. Let's filter such case.

Closes #12585

NO_DOC=bugfix

Co-authored-by: Serge Petrenko <sergepetrenko@tarantool.org>
(cherry picked from commit 6adf3f407)

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