[knot-dns-users] PID files are passé

Dear knot users/developers, I'm testing Knot 1.3.0-rc2. One issue I've run into is when knot exits uncleanly. In this case, it leaves its PID file behind in /var/lib/knot/knot.pid. On the following attempt to start knot, it sees the PID file, and refuses to start, so I have to remove the stale PID file by hand. If I run knot under a supervisor, such as upstart, then it tries to run knot, fails, tries again rapidly in succession, and eventually gives up, at which point knot isn't running. My first observation is that in cases where knot is running under a supervisor, the PID file is not necessary. The supervisor knows knot's PID, and can signal it directly (to reload, or stop). Could you consider making the PID file optional? As in, if in knot.conf, I have: pidfile ""; then knot should not attempt to write (or read or delete) a PID file at all. Alternatively, could you make knot a bit smarter so that if it detects a PID file at startup, but that PID is either not in use, or the process using it is not knot, then it should remove the PID file? Without either of these possibilities, I have to add logic in my startup scripts or supervisor scripts to remove any stale PID files. If I only had one instance of knot, I could do that simply with "rm -f /var/lib/knot/knot.pid", but I'd like to run multiple instances of knot, and so I would have multiple PID files, whose locations I would have to extract from the config file first in order to delete them reliably. This starts to get hairy... I hope I have made a reasonable case for providing an option to not record a PID file, or clean up one before starting. My preference is for the first option, ie. not writing a PID file. Regards, Anand Buddhdev RIPE NCC