Several months ago, I started a little project at work, called Mockload. It started as a fun way of using the MySQL Proxy, to test our monitoring agent, as well as the rules engine and graphs on the Service Manager.

Why?
I needed a tool that would be easy to use, and improve over time. And that it would allow our QA team to send custom values to the service manager. The goal was to pretend having some very busy MySQL servers.

And what better tool, than the MySQL Proxy itself to pretend being a busy MySQL Server!
The way our agent collects the MySQL related data, is by issuing different sql queries. So, I thought that I could have a MySQL proxy instance in between …

A couple of weeks ago I wrote a lua script to use with the MySQL Proxy that transforms the Proxy into a key=>value lookup dictionary.

But I couldn't just stop there. So I decided to add replication to it :).


The basic idea is that you have one proxy that acts like a master, it can handle all write/read operations. Once it receives a write query, it will send that query to the slave proxy instances, and after the last slave gets the query, the master will return a confirmation to the mysql client.
And of course, you send your read queries to the slave proxy instances.

Show me the code.
It is available on the …

There are times when you don't need a MySQL server to handle your queries, this could come handy when you are automating tests, or writing interesting Lua scripts.

Yes, you can use the MySQL Proxy for this as well. And have it pretend to be a MySQL server.
Today we'll focus on a simple implementation. We will handle an initial connection, a SHOW DATABASES query and the exit (QUIT) command.

You can see all the hooks that the proxy handles on this Lua script written by Giuseppe

Connecting to a server. …

While I hope the MySQL Proxy never crashes, it will happen, there will be some strange (or maybe not so strange) usage or workload and it will die.

To avoid this, you could decide not to use it, or maybe you could use something like Linux HA to have more than one MySQL Proxy running at all times. Or you could use one of the new features that comes with the version 0.7.0.

What is it?
We now have a --keepalive option. As the name indicates, if the mysql proxy process dies/crashes, it will come back up in a few seconds (less than 5 seconds).

How does it work?
If you start the MySQL Proxy with the keepalive option, there will be two processes with the same name. One will be very small, about 600KB. and then you …

What I really like about having Lua and MySQL Proxy together is that it turns out to be very flexible, you can have the proxy do all kinds of things. And the last thing I made the MySQL Proxy do is to act like memcached.

Well, maybe not, but it handles key => value pairs now :P




What does it do?

It handles 5 basic query types:

mysql> INSERT "key" = "value";

Very simple, insert a key => value pair on a proxy.global.db table, if there is already a value for that query, it will overwrite it.

mysql> SELECT "key";

It retrieves the value for the specified key.

mysql> DELETE "key";

Deletes the key …

We have an Admin plugin for the MySQL Proxy, but people started asking how to use it. I only found one example, thanks to Giuseppe, but people wanted more.

While the admin plugin is somehow limited, it already provides some nice features. One of the use cases is to give access to information to only authorized users. The Admin plugin uses its own username and password to authenticate users. This is not related to any user on your MySQL server.

The example.

I went ahead and put two scripts together in about an hour. They are basic, but should give you more of an idea of what you can do.

Number of queries …

After I wrote about reading a master.info file using the MySQL Proxy, I went ahead and added the missing piece. Creating a master.info file using the MySQL Proxy.

A bug?
As I went back to lib/mysql-proto.c looking for a function that I could duplicate and modify to add the to_masterinfo_string() function, I realized that I missed a few master_ssl_* fields. It turned out that I was not exporting all the fields from the master.info file.

This time, the bug fix was easy enough. After modifying the test case to account for the missing fields, I added a …

After I wrote about a new feature on MySQL Proxy that helps you read master.info files, I thought that showing an example could come handy.

You can find the complete file on the MySQL Forge and once I have a test case for this script, it will be available on Launchpad.

Explaining the code.
You can see at the top I have

local proto = assert(require("mysql.proto"))

This is important, as it makes the from_masterinfo_string() function available for use.

I also included a function called get_command(), which is a modification of code found …

This time I'll write about a nice featured we now have on the MySQL Proxy.

Parsing master.info
The master.info is a file that the MySQL server creates when you are running a slave server, you can read the manual for more details.
And now you can use the MySQL Proxy to read that file and parse the data from it.

Background
It all started when Jan emailed the proxy discuss mailing with the Changelog from 0.6.1 to 0.7.0. The part that got my attention was:
"...
Core
[skip]
* added parser for master.info files"
... "
As I was working on a Lua script that did some simulation, I …

Thanks to Kay, it is now much easier to contribute to the MySQL Proxy project. And it turns out you don't have to be a super C developer to help out.
Yes, you may think, you can report bugs, help answering questions, even submit Lua scripts. But there is another way you can contribute.

Blueprints
You can check out the blueprints for the Proxy and pick one that seems "simple" to implement. That's what I did. I went there and picked " …