Improved routing hint documentation.

This commit is contained in:
Markus Makela
2015-06-23 19:51:19 +03:00
parent bf6eea38aa
commit b3df3ea7a2

View File

@ -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 <hint>
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 <hint body>
```
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 <server name>]
```
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 <server name> 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 <param>=<value>
```
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 <hint name> prepare <hint content>
```
Pushing a hint onto the stack:
```
-- maxscale <hint name> 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 <hint name> begin <hint content>
```
You can also push anonymous hints onto the stack which are only used as long as they are on the stack:
-- maxscale begin <hint content>
```
-- maxscale begin <hint content>
```