a HA daemon ... first ideas

i have a project where veritas manages various fail over szenarios with lots of middelware involved and all the corporate nightmare you want to have. the problem now is that they want to manage a fail over between two database servers and the connected middleware without veritas ... and so they asked me to write "something".

having thought about it for one day now i looks like i could write a quite general soloution that could be deployed in various situations where you have a master and a hot standby slave. so, lets write a HA daemon.

what does a HA daemon?

the main goals of a HA daemon is to monitor states and act according to state changes. that's all the magic. so how can we do that? my current idea is to implement an internal state hash that learns the environment and reads a set of rules. every now and then some checks get forked and the checks write results back to the main daemon. if the daemon encounters state changes it tries to trigger actions that were defined for those state changes. and starts monitoring the environment again.

interesting things...

well, i have never written a language parser before and that is something i really wanted to do some when so, yes, this is the moment. as the rules have to be defined somehow we need a parser that reads the rules and interprets them and moves them in any kind of internal data structure that can be used by the daemon. thins is an interesting one.
forking off checks after a certain time that report back to a main daemon. this is a cron like environment where you can define tests that run on defined times.
completely self contained ... this is a hard one. they don't want to install tons of CPAN modules so i have to write everything from scratch.

where could it go?

there is currently the plan to write the daemon and a basic CLI for it. there could, however, some when be a web interface for it, there could be a general thing that does all kinds of fail overs or simply actions ... probably i can even convince them to make an opensource project of it. lets see.