I was going through my old files and came across my notes on MQ and thought I’d share some reasons to use MQ vs. HTTP:
- If your consumer processes at a fixed rate (i.e. can’t handle floods to the HTTP server [bursts]) then using MQ provides the flexibility for the service to buffer the other requests vs. bogging it down.
- Time independent processing and messaging exchange patterns — if the thread is performing a fire-and-forget, then MQ is better suited for that pattern vs. HTTP.
- Long-lived processes are better suited for MQ as you can send a request and have a seperate thread listening for responses (note WS-Addressing allows HTTP to process in this manner but requires both endpoints to support that capability).
- Loose coupling where one process can continue to do work even if the other process is not available vs. HTTP having to retry.
- Request prioritization where more important messages can jump to the front of the queue.
- XA transactions – MQ is fully XA compliant – HTTP is not.
- Fault tolerance – MQ messages survive server or network failures – HTTP does not.
- MQ provides for ‘assured’ delivery of messages once and only once, http does not.
- MQ provides the ability to do message segmentation and message grouping for large messages – HTTP does not have that ability as it treats each transaction seperately.
- MQ provides a pub/sub interface where-as HTTP is point-to-point.
