After a very long time distracted with other projects, I finally added the third component of the MyCAT project: binlog_mon, a binary log manager for MySQL.

The main feature of this tool is that it has two disk usage thresholds which determine when it purges your binary logs:

• a lower, "nominal", threshold above which binary logs will be purged if-and-only-if none of the replication slaves are still reading it,
• and a higher, "critical", threshold at which the behavior is configurable.
  

It can simply send you an alert if disk usage is above critical and the oldest file is still needed - or it can purge 1 file, all files until usage below critical, or all files until usage below nominal levels. (Other options could be added fairly easily.) The "critical" option is so configurable because purging any binary …

I just finished a couple day's work, documenting and adapting the 'rcall' (Remote Call) tool, and added it to the Mycat project on sourceforge. The readme is available here.

'rcall' is designed to run in non-homogeneous *nix clusters, to ease use of these clusters by creating a single place from which to securely run commands across logical groups of servers.

I'll give some examples.... The past two companies I have worked for both had separate web (apache) servers, mailing (MTA) servers, and database (MySQL) servers. Using rcall (its previous incarnation, that is), I was able to easily track down an error that was causing seemingly random entries in the databases to have wrong timestamps; `rcall -on web -C 'date'` would print the current date on each web server, making it easy to see …

Finally! Last night, I put the finishing touches on the documentation, and uploaded to SourceForge. Well, finishing touches for a first alpha, hehe - still, it's a good step! Anyone with Perl installed should be able to download Mycat-0.1.2.tgz, untar, edit the config file (mycat.cnf), and run rep_mon.pl to see the status of replication on their servers.

Mycat-0.1.2 release notes

I will add the "rcall" script next, but I can't decide whether it's name comes from "Run Command on all" or "Remote Call"... decisions, decisions... anyhow, rcall relies on ssh key-based remote execution of commands, and is not specific to any MySQL installation. It is none the less an indispensable tool for me, when working with large …

I posted the source to my replication monitor (rep_mon.pl) over at sourceforge, along with a screen shot of it in action. It doesn't look all that fancy, but when you've got a dozen MySQL servers, it sure helps to have one script that checks them all at once!