I have a scenario where publishers need to send messages to a known exchange (they won't know the downstream queues directly). Most of the messages should be delivered to every bound queue (like a fanout), but some need to be delivered only to a specific bound queue. I'd like to avoid multiple exchanges as well as multiple queue bonds.
My current solution uses header routing, where a message has one of two headers, identify it as "global" or "specific to a particular sub", where the downstream queues are bound on a match-any to both of those headers. I think this will work, but I feel like there should be a simpler solution.
I tried to find an exchange plugin that would "fanout all messages except specific ones", but I couldn't find such a plugin. Outside of that, any ideas on how to implement such a routing strategy?
For what it's worth, my original solution using a "headers" exchange with queues bound using "match any" is the only one I could find, short of writing a new exchange plugin. It does work and so far seems reasonably fast (at least not measurably slower than a typical "topic" exchange--which I could find no way to apply in this scenario).
From my research on this topic, the ideal solution would be a "topic" exchange with the ability to use a RegEx or at least some form of "or-logic". I did find some information that implied that a RegEx was considered but decided against (in favor of the "dotted notation" topic format) because the latter was faster, specifically because the use a a RegEx would require that every binding be evaluated on each new message (i.e. there was no way to construct a "search shortcut").
For now, my "match-any headers exchange" solution will serve my purposes, but in the future, a "topic" exchange that allowed "or-logic" might be worth exploring. It would allow multiple topic patterns to be achieved with single-binding, without the overhead of a RegEx. But I have no experience with Erlang, nor the time to learn enough of it to write the necessary plugin. Please contact me if anyone is interested in collaborating on this.