diff --git a/Reference/Hint-Syntax.md b/Reference/Hint-Syntax.md index 264d264f6..b84bb85fd 100644 --- a/Reference/Hint-Syntax.md +++ b/Reference/Hint-Syntax.md @@ -1,42 +1,97 @@ # Hint Syntax -Use either ’-- ’ (notice the whitespace) or ’#’ after the semicolon or ’/* .. */’ before -the semicolon. +## Enabling routing hints -The MySQL manual doesn’t specify if comment blocks, i.e. ’/* .. */’, should contain a w -hitespace character before or after the tags. +To enable routing hints for a service, the hintfilter module needs to be configured and the filter needs to be applied to the service. -All hints must start with the ’maxscale tag’: - -- maxscale - -The hints right now have two types, ones that route to a server and others that contain +Here is an example service which has the hint filter configured and applied. + +``` +[Read Service] +type=service +router=readconnroute +router_options=master +servers=server1 +user=maxuser +passwd=maxpwd +filter=Hint + +[Hint] +type=filter +module=hintfilter + +``` + +## Comments and comment types + +The client connection will need to have comments enabled. For example the `mysql` command line client has comments disabled by default. + +For comment types, use either `-- ` (notice the whitespace) or `#` after the semicolon or `/* .. */` before the semicolon. All comment types work with routing hints. + +The MySQL manual doesn`t specify if comment blocks, i.e. `/* .. */`, should contain a w +hitespace character before or after the tags, so adding whitespace at both the start and the end is advised. + +## Hint body + +All hints must start with the `maxscale` tag. + +``` +-- maxscale +``` + +The hints have two types, ones that route to a server and others that contain name-value pairs. -Routing queries to a server: +###Routing destination hints + +These hints will instruct the router to route a query to a certain type of a server. +``` -- maxscale route to [master | slave | server ] +``` -The name of the server is the same as in maxscale.cnf +A `master` value in a routing hint will route the query to a master server. This can be used to direct read queries to a master server for a up-to-date result with no replication lag. A `slave` value will route the query to a slave server. A `server` value will route the query to a named server. The value of needs to be the same as the server section name in maxscale.cnf. -Creating a name-value pair: +### Name-value hints + +These control the behavior and affect the routing decisions made by the router. + +``` -- maxscale = +``` -Currently the only accepted parameter is -’max_slave_replication_lag’ +Currently the only accepted parameter is `max_slave_replication_lag`. This will route the query to a server with lower replication lag then what is defined in the hint value. + +## Hint stack Hints can be either single-use hints, which makes them affect only one query, or named hints, which can be pushed on and off a stack of active hints. Defining named hints: + +``` -- maxscale prepare +``` Pushing a hint onto the stack: + +``` -- maxscale begin +``` Popping the topmost hint off the stack: + +``` -- maxscale end +``` You can define and activate a hint in a single command using the following: + +``` -- maxscale begin +``` You can also push anonymous hints onto the stack which are only used as long as they are on the stack: --- maxscale begin \ No newline at end of file + +``` +-- maxscale begin +```