Stan Hu <[email protected]> wrote: > My unicorn.rb has two listeners: > > listen "127.0.0.1:8080", :tcp_nopush => false > listen "/var/run/unicorn.socket", :backlog => 1024
Fwiw, lowering :backlog may make sense if you got other hosts/instances. More below.. > We found that because of the greedy attempt to accept new connections > before calling select() in > https://github.com/defunkt/unicorn/blob/981f561a726bb4307d01e4a09a308edba8d69fe3/lib/unicorn/http_server.rb#L707-L714, > listeners on another socket stall out until the first listener is > drained. We would expect Unicorn to round-robin between the two > listeners, but that doesn't happen as long as there is work to be done > for the first listener. We've verified that deleting that `redo` block > fixes the problem. > > What do you think about the various options? > > 1. Only running that redo block if there is one listener That seems reasonable, or if ready.size == nr_listeners (proposed patch below) > 2. Removing the redo block entirely >From what I recall ages ago, select() entry cost is pretty high and I remember that redo helping a fair bit even in 2009 with simple apps. Syscall cost is even higher now with CPU vulnerability mitigations, and Ruby 1.9+ GVL release+reacquire is also a penalty I didn't have when developing this on 1.8. Do you have time+hardware to benchmark either approach on a simple app? I no longer have stable/reliable hardware for benchmarking. Thanks. Totally untested patch to try approach #1 diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb index a52931a..69f1f60 100644 --- a/lib/unicorn/http_server.rb +++ b/lib/unicorn/http_server.rb @@ -686,6 +686,7 @@ def worker_loop(worker) trap(:USR1) { nr = -65536 } ready = readers.dup + nr_listeners = readers.size @after_worker_ready.call(self, worker) begin @@ -698,7 +699,6 @@ def worker_loop(worker) # but that will return false if client = sock.kgio_tryaccept process_client(client) - nr += 1 worker.tick = time_now.to_i end break if nr < 0 @@ -708,7 +708,7 @@ def worker_loop(worker) # we're probably reasonably busy, so avoid calling select() # and do a speculative non-blocking accept() on ready listeners # before we sleep again in select(). - unless nr == 0 + if ready.size == nr_listeners tmp = ready.dup redo end And `nr' can probably just be a boolean `reopen' flag if we're not overloading it as a counter. -- unsubscribe: one-click, see List-Unsubscribe header archive: https://yhbt.net/unicorn-public/
