beta-0.6.8 : thresholds up to microseconds!

beta-0.6.8 is out today.

This includes a fix for the startup procedure after a hard fail (the bug being that we couldn't start the
ssh-agent properly due to a conflict with the previous socket), and a major change in the thresholds system.

The cluster now supports thresholds in seconds (as up until now), milliseconds and microseconds (reliablilty depends on hardware, man usleep for more info).

I've changed all invocations to the sleep function for usleep, except in the main loops, and I'm giving admins the chance to express THRESHOLDS in seconds (no units), milliseconds (ms) and
microseconds (us) in /etc/mysql-ha.

The variables affected are:

MONITOR_CHK_THRESHOLD
MYSQL_KILL_WAIT
MYSQL_RESTART_WAIT
SIG_KILL_WAIT

This will be updated in the Installation Guide tomorrow.

I believe this gives administrators much more control over the cluster and takeover/recover time, though it needs proper documentation in the Guide, because if the values are too low for your environment (bad network, loaded server) you can have a false positive. Still, I've taken some good measures to prevent a false positive failover/takeover from happening.

Please go grab this, and happy clustering!