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Update limitations document on wait_timeout

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The document now describes readwritesplit's behavior when wait_timeout is
configured to a low value.
This commit is contained in:
Markus Makela 2016-08-30 10:17:35 +03:00
parent 248a58629b
commit 71bc30be5b
1 changed files with 22 additions and 8 deletions
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30
Documentation/About/Limitations.md
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@ -26,24 +26,24 @@ Workaround: Ensure that socket paths and ports are valid.
Issues [MXS-710](https://jira.mariadb.org/browse/MXS-710) and
[MXS-711](https://jira.mariadb.org/browse/MXS-711) relate to this.
## Limitations with MySQL Protocol support
## Limitations with MySQL Protocol support (MySQLClient)
Compression is not included in MySQL server handshake
## Limitations with Galera Cluster Monitoring
## Limitations with Galera Cluster Monitoring (galeramon)
The default master selection is based only on MIN(wsrep_local_index). This
can be influenced with the server priority mechanic described in the
[Galera Monitor](../Monitors/Galera-Monitor.md) manual.
## Limitations in the connection router
## Limitations in the connection router (readconnroute)
* If Master changes (ie. new Master promotion) during current connection
the router cannot check the change.
* Sending of binary data with LOAD DATA LOCAL INFILE is not supported
## Limitations in the Read/Write Splitter
## Limitations in the Read/Write Splitter (readwritesplit)
Read queries are routed to the master server in the following situations:
@ -56,6 +56,20 @@ Read queries are routed to the master server in the following situations:
* if there are multiple statements inside one query e.g.
`INSERT INTO ... ; SELECT LAST_INSERT_ID();`
### Backend write timeout handling
The backend connections opened by the readwritesplit will not be kept alive if
they aren't used. To keep all of the connections alive, a session command must
be periodically executed (for example `SET @a = 1;`).
If the backend server is configured with a low
[wait_timeout](https://mariadb.com/kb/en/mariadb/server-system-variables/#wait_timeout),
it is possible that connections get closed during long sessions. It is
recommended to set the wait_timeout to a high value and let 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
When a multi-statement query is executed through the readwritesplit
@ -177,7 +191,7 @@ possible that a slave fails to execute something because of some
non-fatal, temporary failure, while the execution of the same command
succeeds in other backends.
## Authentication Related Limitations
## Authentication Related Limitations (MySQLAuth)
* MariaDB MaxScale can not manage authentication that uses wildcard matching in hostnames
in the mysql.user table of the backend database. The only wildcards that can be
@ -191,7 +205,7 @@ succeeds in other backends.
backend database. This results in failed connections and unusable usernames
in MariaDB MaxScale.
## Schemarouter limitations
## Schemarouter limitations (schemarouter)
The schemarouter router currently has some limitations due to the nature of
the sharding implementation and the way the session variables are detected
@ -220,12 +234,12 @@ and routed. Here is a list of the current limitations.
the query will be routed to the first available server. This possibly
returns an error about database rights instead of a missing database.
## Dbfwfilter limitations
## Database Firewall limitations (dbfwfilter)
The Database Firewall filter does not support multi-statements. Using them
will result in an error being sent to the client.
## Avrorouter limitations
## Avrorouter limitations (avrorouter)
The avrorouter does not support the following data types and conversions.