Keep Alive Bug

[Maxim Dounin]

Hello!

On Wed, Nov 03, 2010 at 11:47:50PM +1100, SplitIce wrote:

> With keep alive enabled I regularly get issues where requests are combined,
> it seems to depend on the status of a background XMLHTTP request as to
> whether or not they will be combined.
> 
> The output I get is like:
> 
> ,{"id":147,"user":{"username":"dursun123123","sitename":"The Warez
> Scene","profile_url":"#"},"message":"HELLO","time":1288710293},{"id":148,"user":{"username":"hacker3w0rlds","sitename":"The
> Warez Scene","profile_url":"#"},"message":"hello
> all","time":1288710537},{"id":149,"user":{"username":"shootie","sitename":"The
> Warez Scene","profile_url":"#"},"message":"ham","time":1288724254},{"id":150,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"superfly1972","time":1288725995},{"id":151,"user":{"username":"dursun123123","sitename":"The
> Warez Scene","profile_url":"#"},"message":"HELLO","time":1288728745},{"id":152,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"madsen","time":1288730813},{"id":153,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"RILEY
> RILEY","time":1288734307},{"id":154,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"WalterBosque-art.com","time":1288740171},{"id":155,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"what
> up","time":1288744021},{"id":156,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":"whats the best jenna
> presley scene???","time":1288744066},{"id":157,"user":{"username":"Anonymous","sitename":"The
> Warez Scene","profile_url":"#"},"message":":D","time":1288763786},{"id":158,"user":{"username":"Anonymous","sitename":"TWS","profile_url":""},"message":"drive
> mender","time":1288782574},{"id":159,"user":{"username":"Anonymous","sitename":"TWS","profile_url":""},"message":"forensic","time":1288783532}]HTTP/1.1
> 200 OK
> Server: nginx/0.8.52
> Date: Wed, 03 Nov 2010 12:45:29 GMT
> Content-Type: text/html; charset=UTF-8
> Transfer-Encoding: chunked
> Connection: keep-alive
> X-Powered-By: PHP/5.3.3-0.dotdeb.1
> Cache-Control: private, no-cache="set-cookie"
> Expires: 0
> Pragma: no-cache
> Content-Encoding: gzip
> 
> 40b9
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> 
> 
> The first is the JSON output of a shoutbox currently requesting on that
> page, the second portion is the real page.
> 
> With keepalive disabled this does not occur. Data is being fetched via
> proxy_pass to remote host. Shoutbox is using POST requests ever 10 seconds.

If you are able to reproduce the problem - you may want to provide 
more info, i.e. what happens on wire (use tcpdump/wireshark/etc) 
between client and nginx, as well as nginx -V output, config and 
debug log.

See here for more info:

http://wiki.nginx.org/Debugging

Note well: there are some known bugs which may introduce protocol 
breakage and cause wierd effects on kept alive connections.  Most 
frequently mentioned one is related to caching of 0-sized replies 
from backend without Content-Length set.  See here for patches:

http://nginx.org/pipermail/nginx-devel/2010-January/000100.html
http://nginx.org/pipermail/nginx-devel/2010-January/000101.html
http://nginx.org/pipermail/nginx-devel/2010-January/000102.html

Maxim Dounin