mysql-proxy-discuss team mailing list archive

[Kay Röpke <Kay.Roepke@xxxxxxx>]

Hi!

On Jun 16, 2009, at 5:00 PM, Brian Zammit wrote:

> Hello again list,
>
> I want to use mysql-proxy to create a simple pair of proxy  
> applications. One
> for reads, one for writes that are split at the application level.
>
> The write configuration is currently:
> --daemon --proxy-skip-profiling --proxy-address=localhost:4040
> --admin-address=localhost:4041 --proxy-backend- 
> addresses=10.10.10.10:3306
>
> The read configuration is currently:
> --daemon --proxy-skip-profiling --proxy-address=localhost:4050
> --admin-address=localhost:4051
> --proxy-backend-addresses=10.10.10.20:3306--proxy-backend-addresses=
> 10.10.10.21:3306
>
>
> I want the read servers to be load balanced, and have read servers
> automatically fall out and rejoin the pool on failure/recovery. Does  
> the
> configuration above make sense, or should I be using --proxy-
>
> read-only-backend-addresses for the read configuration to have this  
> work
> properly?

If you are using a lua script you can pick any backend (read/write or  
read-only) you like.
The default implementation written in C will skip read-only backends  
when looking for
a backend to connect to, because that's the most reasonable thing to  
do if we don't know what
the connection will be used for (you don't want a slave being selected  
for a random client
that might want to write).

I think if you don't want to provide a script that implements  
connect_server and can ensure
in the application level that no writes will be issued on slaves, then  
using
--proxy-backend-addresses is what you want.

> Suggestions on the most convenient way to watch the queries flow  
> through the
> proxies to make sure queries are going where they should?


There are a couple of options for doing so:
You could use a lua table in proxy.global to track the number of  
queries send to a specific backend index,
or you could write that information to the log file.
If you choose the proxy.global table version, you would have to either  
add something to the admin script
to be able to query that information or log it in regular intervals.

Check out the tutorial-resultset.lua file for a simple example of the  
global counter version.

cheers,
-k
--
Kay Roepke
Software Engineer, MySQL Enterprise Tools

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