Out of interest, why do we have to wait [a hard coded timeout]? Why can't we wait for all events to finish (and maybe just ignore all new incoming connections?)

all events to finish

may take a long time (minutes) depending what was going in in the past?

@MarcoFalke but this doesn't stop new connections (or is that done elsewhere?) in that waiting time. So conceptually, the status quo could be the same?
That is, new connections coming in, old ones still finishing.

New connections are stopped just above, see where the accept sockets are torn down.

Though it does look like we should close connected sockets in http_reject_request_cb as well for good measure. @laanwj Is there a reason to keep them open once they've had a req rejected?

• Waiting for all events to finish could take forever. There's tons of ways that someone could keep a connection option by slowly sending data. Also, timing events (such as the walletpassphrase timeout) may hold up the event queue.
• Just breaking off everything in progress immediately prevents the answer to stop from getting back. We could just declare this a feature of course and be done with it... But it was a race condition, sometimes you would get a reply, sometimes not. We could define stop to cease all RPC activity immediately. But I think I like this better.
• There AFAIK is no way to ask libevent, nor libevent_http if the events in the queue are important enough to wait for or not. And specially tagging the connection that sends 'stop' is quite ugly, not sure if even possible without diving into internal data structures.

For context read #6719.

I'm not 100% happy with this solution either, but I wasn't able to find another way to do it, and it's better than the previous one.

@cfields sure, you can close the connection afterwards there, but that doesn't solve this issue.

@MarcoFalke but this doesn't stop new connections (or is that done elsewhere?) in that waiting time. So conceptually, the status quo could be the same?

It does:

        // Unlisten sockets
        BOOST_FOREACH (evhttp_bound_socket *socket, boundSockets) {
            evhttp_del_accept_socket(eventHTTP, socket);
        }
        // Reject requests on current connections
        evhttp_set_gencb(eventHTTP, http_reject_request_cb, NULL);

This closes the port and makes new requests error (so that no new work items are created). But that's best-effort. Current connections could still do e.g. a slowloris attack. The two seconds are a belt and suspenders, nothing more.