Good to know about potential performance problems. I don't plan to have more than 5 hosts. Also, good to know about MQTT.
On Sun, Jul 12, 2020 at 8:52 AM Andrew Smith <laconi...@gmail.com> wrote: > On Sun, 12 Jul 2020 at 21:39, Rita <rmorgan...@gmail.com> wrote: > >> Thats good to know. Are there some standard patterns or best practices I >> should follow when using messaging and with listen/notify? >> >> On Sat, Jul 11, 2020 at 1:44 PM Brian Dunavant <dunav...@gmail.com> >> wrote: >> >>> One aspect is if there is no one listening when a notify happens, the >>> message is lost (e.g. no durability). If this is important to you, it can >>> be addressed by writing the messages to a table as well when you NOTIFY, >>> and the listener deletes messages after they are processed. On connection >>> the listener can query the table to catch up on any missed messages, or >>> messages that were mid-process during a crash. This is trickier with more >>> than one listener. This isn't a whole lot more efficient than just using >>> the table alone, but it saves you from having to poll so better response >>> times. >>> >>> On Sat, Jul 11, 2020 at 8:58 AM Rita <rmorgan...@gmail.com> wrote: >>> >>>> I am investigating various pub/sub tools such as ActiveMQ, Rabbit, >>>> Redis, etc.I came across Postgresql Listen/Notify and was easily able to >>>> write code to listen to messages. For the people who have been using this >>>> for a while: what are its downsides, things to consider when writing good >>>> code that use pub/sub, how do you deal with large messages, can I have >>>> subscribers listen to replica nodes? >>>> >>>> Thanks >>>> -- >>>> --- Get your facts first, then you can distort them as you please.-- >>>> >>> > A couple of years ago I started looking into listen/notify in PG10 and > found that the throughput decreased quite a bit as I added more and more > listeners. Given the number of apps I needed to have listening and the > number of messages that I expected to be consuming, I ended up writing a > single listener app which then republished the messages via MQTT. Not sure > if the performance has improved in subsequent versions (or whether this > will affect you at all) but it's something to keep in mind. > -- --- Get your facts first, then you can distort them as you please.--
