Should I close the channel/connection after every publish?
I am using amqplib in Node.js, and I am not clear about the best practices in my code.
Basically, my current code calls the amqp.connect() when the Node server starts up, and then uses a different channel for each producer and each consumer, never actually closing any of them. I'd like to know if that makes any sense, or should I create the channel, publish and close it every time I want to publish a message. And what about the connection? Is that a "good practice" to connect once, and then keep it open for the lifetime of my server?
On the Consumer side - can I use a single connection and a single channel to listen on multiple queues?
Thank you for any clarifications
Answer
In general, it's not a good practice to open and close connections and channels per message. Connections are long lived and it takes resources to keep opening and closing them. For channels, they share the TCP connection with the connection so they are more lightweight, but they will still consume memory and definitely should not be left open after done using them.
It is recommended to have a channel per thread, and a channel per consumer. But for publishing it is totally ok to use the same channel. But keep in mind that depending on the operations, the protocol might kill the channel in certain situations (e.g. queue existence check), so prepare for that. There is also soft (configurable) and hard (usually 65535) limits on the maximum number of channels on many of the client implementations.
So to sum up, depending on your use case use one to a few connections, open channels when you need them and share them when it makes sense, but remember to close them when done.
The rabbitmq documentation explains the nature of the connections and channels (end of the document). And the accepted answer on this question has good information on the subject.