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From Julian Santander <>
Subject [users@httpd] Avoid buffering in a reverse proxy configuration
Date Mon, 22 Oct 2007 18:14:05 GMT
Hello there,

    I hope you can help or at least point me in the right direction.

    I'm currently trying to setup an Apache 2.2.6 for cygwin as a 
Reverse Proxy in front of a different server. This server is expected to 
produce long (in time) response as a series of chunk-encoded pieces 
(actually each of those pieces represent asynchronous events relayed to 
a client of about 500-600 bytes).

    The proxying is working fine, but what I'm observing is that the 
reverse proxy buffers do not send the chunks as they're received, but it 
waits to have a big response (something in the order of ~8000 bytes) to 
send the data to the socket (or for the response to be closed). As you 
can imagine this affecting the real-timeliness of the delivery of my 

    I've been playing with different parameters:

ProxyIOBufferSize  10 [although from looking at the code it seems it 
cannot be less that 8192]
SendBufferSize 512
ReceiveBufferSize 512
ProxyReceiveBufferSize 512

    With no actual change.
    However I'm not even sure whether the configuration that needs to be 
changed is in the mod_proxy or in the a more central part of the httpd.

    I even tried to turn on the mod_dumpio and the traces shown that 
dumpio_in and dumpio_out where being shown as the chunk were 
received.... and I didn't see any trace for when the packet was really 
sent to the client.

    Is there any configuration setting, module or anything I'm missing? 
I've run out of combinations of reverse proxy, buffer, flush, response 
to google for.

    I'm tempted to change the code that sets ProxyIOBufferSize  to a 
lower value and recompile the mod_proxy.

    Thanks very much in advance and best regards


Julian Santander
IN Application Development		   Tel: +34 91330 5146
Alcatel-Lucent España	<>
Ramírez de Prado, 5                         28045 Madrid Spain

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