Hello! This is my first post so sorry if I break some community guidelines, if I do so, it is unknowingly. This could be more of a discussions topic. This is a post / general-question about pubsub and people’s experiences with it. I’ve been evaluating the Phoenix.Pubsub module and trying to unders…

[image] blquinn: Reading a bit of source code shows me that every time that you “subscribe” (add a proc to the process group) it does a global transaction around the name of the group. I believe that this has to contact all nodes and acquire some type of dist. lock. This seems like it would be …

Thanks for the quick thorough reply, and from the creator of Phoenix no less! Sounds like I made a few assumptions about Phoenix.Pubsub and you know what they say about that. Correct me if I’m wrong: subs are stored locally only, and messages that are broadcasted via pubsub are always sent to all …

[image] blquinn: Correct me if I’m wrong: subs are stored locally only, and messages that are broadcasted via pubsub are always sent to all nodes, correct? Correct, unless you use direct_broadcast to send to a single node, all nodes receive it. [image] blquinn: If this is the case, that …

True, your points about the load tests make sense. I do think that, while any tests are nice to see, they need to be a little more real world to be truly valuable. In order to prove the actual throughput of the system, it should run clustered, then each client should create a bunch of subscriptions…

I’m also highly interested in this. I’m just getting started with elixir development but have a great dream in developing something like Apache Pulsar or one of the big Paid for PubSub platforms in Elixir.

[image] chrismccord: Phoenix.PubSub has no durable pubsub adapter today Does this mean there might be one day? :slightly_smiling_face: Curious, what might be the ideal approach?

Phoenix.Pubsub subscriptions performance

Questions & Help Questions

jam May 12, 2026, 7:20pm 7

Does this mean there might be one day? Curious, what might be the ideal approach?