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MXS-2834: Make retrying of trx deadlocks configurable

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The behavior is not desirable in all cases and should be enabled only if
needed.
This commit is contained in:
Markus Mäkelä 2020-01-11 11:53:01 +02:00
parent 09c55111cc
commit 6c14ac7829
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GPG Key ID: 72D48FCE664F7B19
4 changed files with 18 additions and 1 deletions
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13
Documentation/Routers/ReadWriteSplit.md
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@ -537,6 +537,19 @@ controls how many server and network failures a single transaction replay
tolerates. If a transaction is replayed successfully, the counter for failed
attempts is reset.
### `transaction_replay_retry_on_deadlock`
Enable automatic retrying of transactions that end up in a deadlock. This
parameter was added in MaxScale 2.4.6 and the feature is disabled by
default. MaxScale versions from 2.4.0 to 2.4.5 always tried to replay deadlocked
transactions.
If this feature is enabled and a transaction returns a deadlock error
(e.g. `SQLSTATE 40001: Deadlock found when trying to get lock; try restarting transaction`),
the transaction is automatically retried. If the retrying of the transaction
results in another deadlock error, it is retried until it either succeeds or a
transaction checksum error is encountered.
### `optimistic_trx`
Enable optimistic transaction execution. This parameter controls whether normal

1
server/modules/routing/readwritesplit/readwritesplit.cc
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@ -520,6 +520,7 @@ extern "C" MXS_MODULE* MXS_CREATE_MODULE()
{"transaction_replay", MXS_MODULE_PARAM_BOOL, "false"},
{"transaction_replay_max_size",MXS_MODULE_PARAM_SIZE, "1Mi"},
{"transaction_replay_attempts",MXS_MODULE_PARAM_COUNT, "5"},
{"transaction_replay_retry_on_deadlock",MXS_MODULE_PARAM_BOOL, "false"},
{"optimistic_trx", MXS_MODULE_PARAM_BOOL, "false"},
{"lazy_connect", MXS_MODULE_PARAM_BOOL, "false"},
{MXS_END_MODULE_PARAMS}

2
server/modules/routing/readwritesplit/readwritesplit.hh
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@ -161,6 +161,7 @@ struct Config
, transaction_replay(params->get_bool("transaction_replay"))
, trx_max_size(params->get_size("transaction_replay_max_size"))
, trx_max_attempts(params->get_integer("transaction_replay_attempts"))
, trx_retry_on_deadlock(params->get_bool("transaction_replay_retry_on_deadlock"))
, optimistic_trx(params->get_bool("optimistic_trx"))
, lazy_connect(params->get_bool("lazy_connect"))
{
@ -225,6 +226,7 @@ struct Config
bool transaction_replay; /**< Replay failed transactions */
size_t trx_max_size; /**< Max transaction size for replaying */
int64_t trx_max_attempts; /**< Maximum number of transaction replay attempts */
bool trx_retry_on_deadlock; /**< Replay the transaction if it ends up in a deadlock */
bool optimistic_trx; /**< Enable optimistic transactions */
bool lazy_connect; /**< Create connections only when needed */
};

3
server/modules/routing/readwritesplit/rwsplitsession.cc
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@ -709,7 +709,8 @@ void RWSplitSession::clientReply(GWBUF* writebuf, DCB* backend_dcb)
}
}
if ((error.is_rollback() || error.is_wsrep_error()) && handle_ignorable_error(backend))
if (((m_config.trx_retry_on_deadlock && error.is_rollback()) || error.is_wsrep_error())
&& handle_ignorable_error(backend))
{
// We can ignore this error and treat it as if the connection to the server was broken.
gwbuf_free(writebuf);