Comment by kscarlet

An update: I've spent some time taking a much deeper look, and while I can't guarantee it's perfect, I added a different approach for Clack+Woo, documented here: https://github.com/fsmunoz/datastar-cl/blob/main/SSE-AND-WOO...

In short: I've replace the Common Lisp loop (that works for Hunchentoot since it opens threads, but doesn't for Woo since it blocks) with a deeper integration into the event loop:

> And that was the main change: looking at the innards of it, there are some features available, like woo.ev:evloop. This was not enough, and access to the libev timer was also needed. After some work with lev and CFFI, the SDK now implements a Node.js-style approach using libev timers via woo.ev:evloop and the lev CFFI bindings (check woo-async.lisp).

This is likely (almost surely) not perfect or even ideal, but it does seem to work, and I've been testing the demo app with 1 worker and multiple clients.

I haven't tried Wookie, since adding Clack+Woo was already a substantial change. Reading https://fukamachi.hashnode.dev/woo-a-high-performance-common... , where it compares with Wookie, I'm not sure if it would make a difference: it might be wrong, but "it says:

> Of course, this architecture also has its drawbacks as it works in a single thread, which means only one process can be executed at a time. When a response is being sent to one client, it is not possible to read another client's request.

... which for SSE seems to be similar to what the issue is with Woo. I wrote a bit more on it in https://github.com/fsmunoz/datastar-cl/blob/main/SSE-WOO-LIM... , and it can be more of a "me" problem than anything else, but to keep a SSE stream open, it doesn't play well with async models. That's why I added a with-sse-response macro that, unlike with-sse-connection, sends events without keeping the connection open.