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From Steve Zweep <>
Subject Question about async mod_proxy_wstunnel and threads
Date Thu, 17 Jul 2014 18:09:52 GMT

I am prototyping a system in which we will have a large number of websocket connections between
multiple clients and a server (potentially) behind mod_proxy_wstunnel. Currently I am testing
a trunk build with the event mpm. With ProxyWebsocketAsync turned off, communication between
client and server works well except that an Apache thread is held open for each connection
(which is expected). With ProxyWebsocketAsync enabled, these threads are no longer seen, again
as expected. I see two issues though:

1.       While communication from client to server works well, unsolicited messages from the
server to clients seem to queue. If the client subsequently sends a message back to the server,
the original message from the server is received. I would have expected the data from the
server to generate an event resulting in immediate delivery.

2.       In attempts to debug this I experimented with ProxyWebsocketAsyncDelay. I observed
that when this is used, the connections never go into async mode. I.e. proxy_tunnel_pump()
never returns SUSPENDED. As a result I see the same thread usage as when ProxyWebsocketAsync
is turned off. Is this expected behavior?

Any insights into what is going on here would be helpful. I noticed that there have been a
number of recent changes both to the event mpm and mod_proxy_wstunnel. Perhaps there are still
some known issues with this code?


- Steve

Steve Zweep | Senior Software Engineer
WatchGuard Technologies, Inc. |


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