irule loggin a class caused all Irules using that clase to fail

Well, just looking at the line

log local0.info \"$log_line [$::valid_methods]\"

I've got a couple of questions.

First of all, why are you escaping all the double quotes? Aren't you trying to pass a string to the log command? Don't you want that string quoted?

Second, are you really trying to pass the entire contents of your class to syslog? That's what you're telling the TCL interpreter by having [$::valid_methods] in your log line. I'm not sure why you'd want to do this, as the class is a static piece of the configuration, and this would likely add a fair amount of overhead.

Colin