Hi list. One pattern I've used is for apps to communicate events to each other through the database. ie: - App 1 sents a boolean value to True - App 2 queries the field every 10s, sets the value to False, and does something. Is this reasonable, or should apps avoid this pattern? I have seen the NOTIFY and LISTEN SQL statements. However: 1) App 2 might not be running at the time (eg: it's launched from cron, or it was temporarily stopped), and the expectation is that App 2 will run the special logic when it is started. 2) App 2 is usually single-threaded, and needs to do other things in it's main thread besides wait for a DB notification. I also know of RPC, but haven't used it before, and don't see a need if you can use the above pattern. I would use RPC (or unix signals if on the same host) if App 2 needed to respond quickly, and I didn't want to hammer the DB & network with constant polling. Any comments? David.
