RE: [users@httpd] mod_proxy and keepalive question

Tue, 08 Jan 2008 15:28:59 -0800 


Hi,
thanks for your notes. Still I don't entirely understand what I see. Here's how I tested. I've set up 2 virtualhosts on my ubuntu gutsy notebook (apache 2.2.4, prefork): localhost and localhost-external. 

Here's localhost-external:

<VirtualHost 127.0.0.1:80>
        ServerAdmin [EMAIL PROTECTED]
        ServerName localhost-external
        DocumentRoot /var/www/apache2-default
        ErrorLog /var/log/apache2/error.log
        LogLevel warn
        CustomLog /var/log/apache2/access.log combined
        ServerSignature On
        ProxyPass /proxied http://localhost/internal min=30 smax=190 max=200 
timeout=120 keepalive=On
        ProxyPassReverse /proxied http://localhost/internal
</VirtualHost>

and localhost:

<VirtualHost 127.0.0.1:80>
        ServerAdmin [EMAIL PROTECTED]
        ServerName localhost
        DocumentRoot /var/www/apache2-default
        ErrorLog /var/log/apache2/error.log
        LogLevel warn
        CustomLog /var/log/apache2/access.log combined
        ServerSignature On
</VirtualHost>
Now I've put a small php script called headers.php to both /var/www/apache2-default and /var/www/apache2-default/internal, which dumps all http request header data. If I open url http://localhost-external/headers.php then, among others, there's the Connection: keep-alive header. OK, now I open http://localhost-external/proxied/headers.php, and connection keep-alive is still there. So keep-alive is OK for http backends.
But if I change the ProxyPass and ProxyPassReverse lines in localhost-external to use https instead of http (and set up localhost to serve https), then http://localhost-external/proxied/headers.php shows that the Connection header value changed to "close".
This tells me that it's not possible to use persistent connections to https backends in proxy workers, which is strange, as it seemed to be possible in apache 2.0 mod_proxy. Is this correct or I've made a mistake somewhere? 


Thanks for any help,
Balint


On Tue, 8 Jan 2008, Axel-Stephane  SMORGRAV wrote:


Hi

This is very surprising to me because this is one of the things about 2.2 that 
I was looking forward to and therefore tested specifically.

Roughly speaking httpd 2.2 creates a connection pool for each ProxyPass. Actually it 
associates a "worker" (not to be mixed-up with MPM worker workers or worker 
processes) with each ProxyPass destination, and there is a connection pool associated 
with each worker. Workers and the associated connections persist across client requests. 
You may therefore use persistent backend connections even if the client connection is not.

This works fine in 2.2.4. There was however a bug in 2.2.0 
http://issues.apache.org/bugzilla/show_bug.cgi?id=38602. If you use rewrite rules for 
proxying however, the back-end connections will not be persistent because the default 
worker will be used, and the default worker has only non-persistent connections 
associated with it. There is a way to de-activate keep-alive for back-end connections: 
setting the proxy-nokeepalive environment variable (see the "Protocol 
Adjustments" section of the mod_proxy manual pages).

In 2.0 back-end connections were persistent only of the client connection was 
so. Back-end connections could not be used to serve requests from different 
clients.

For further reading, refer to the mailing list archive for last September 
http://mail-archives.apache.org/mod_mbox/httpd-dev/200709.mbox/thread or my 
Bugzilla report http://issues.apache.org/bugzilla/show_bug.cgi?id=43308

-ascs

-----Message d'origine-----
De : KOZMAN Bálint [mailto:[EMAIL PROTECTED]
Envoyé : mardi 8 janvier 2008 16:45
? : users@httpd.apache.org
Objet : [EMAIL PROTECTED] mod_proxy and keepalive question


Hi there,


I'm experiencing a different behaviour of apache 2.2's mod_proxy compared to the one in 2.0. From 
my point of view the main difference is that 2.0 mod_proxy does not send the "Connection" 
request header to the backend, while 2.2 mod_proxy always sends "Connection: Close" 
regardles whether the backend connection goes through http or https.
The question is if it's possible to use persistent connections from 2.2 mod_proxy to the 
backend (and thus force mod_proxy to send "keep-alive" in the Connection 
header)?


Any help would highly be appreciated, thanks, Balint

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