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MXS-852: Update readwritesplit limitations

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Updated limitations with notes about parallel execution of binary protocol
prepared statements. Remove limitations that have been lifted in 2.2.
This commit is contained in:
Markus Mäkelä
2017-06-23 13:16:30 +03:00
parent 296c1001a2
commit 5c94610b68
1 changed files with 6 additions and 12 deletions
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18
Documentation/About/Limitations.md
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@ -124,7 +124,6 @@ Sending of binary data with `LOAD DATA LOCAL INFILE` is not supported.
Read queries are routed to the master server in the following situations: Read queries are routed to the master server in the following situations:
* query is executed inside an open transaction * query is executed inside an open transaction
* query is a prepared statement
* statement includes a stored procedure or an UDF call * statement includes a stored procedure or an UDF call
* if there are multiple statements inside one query e.g. `INSERT INTO ... ; SELECT * if there are multiple statements inside one query e.g. `INSERT INTO ... ; SELECT
LAST_INSERT_ID();` LAST_INSERT_ID();`
@ -140,19 +139,14 @@ requests without waiting for the protocol to be idle. If you are using the
MariaDB Connector/J, add `useBatchMultiSend=false` to the JDBC connection string MariaDB Connector/J, add `useBatchMultiSend=false` to the JDBC connection string
to disable batched statement execution. to disable batched statement execution.
#### Backend write timeout handling #### Prepared Statement Limitations
The backend connections opened by readwritesplit will not be kept alive if they Readwritesplit does not support the parallel execution of binary protocol
aren't used. To keep all of the connections alive, a session command must be prepared statements that use cursors. In practice this means that only one
periodically executed (for example `SET @a = 1;`). open cursor is allowed when readwritesplit is used.
If the backend server is configured with a low Opening more than one cursor will cause the execution of the prepared
[wait_timeout](https://mariadb.com/kb/en/mariadb/server-system-variables/#wait_timeout), statements to stall.
it is possible that connections get closed during long sessions. It is
recommended to set the `wait_timeout` to a high value and let MariaDB MaxScale
handle the client timeouts. This can be achieved by using the
[_connection_timeout_](../Getting-Started/Configuration-Guide.md#connection_timeout)
parameter for the service.
#### Limitations in multi-statement handling #### Limitations in multi-statement handling