On 23.07.2012 20:36, Carlucci, Tony wrote:
Hello, I’ve been trying to track down an intermittent problem with a
Java web application that is running on tcServer fronted by Apache HTTP
Server. We get intermittent “Server Unavailable / HTTP 500” errors,
and when we do see them, there is the same set of log statements written
to the Apache HTTP Server error log:
[Mon Jul 23 10:03:15 2012] [error] (70014)End of file found:
ajp_ilink_receive() can't receive header
[Mon Jul 23 10:03:15 2012] [error] ajp_read_header: ajp_ilink_receive failed
[Mon Jul 23 10:03:15 2012] [error] (120006)APR does not understand this
error code: proxy: dialog to 127.0.0.1:7071 (127.0.0.1) failed
We are not seeing any error messages in the tcServer logs.
I believe the issue is with the mod_proxy_ajp module but it’s been very
difficult tracking down what exactly the problem is. What’s
interesting is that this Apache / tcServer configuration is used with
other applications that work just fine and never have the intermittent
500 error. We also can run our application strictly in Tomcat (no
Apache front) without any intermittent errors.
We haven’t ruled out that there could be something in our Java
application code that is causing this, in combination with the
mod_proxy_ajp module, but we have hit a wall as to what this issue could
be. Has anyone else experienced a similar intermittent issue combined
with the above error messages? Below is a copy of the error log and
some configuration settings.
You might want to check the following discussion thread:
http://marc.info/?t=123905265500007&r=1&w=2
To actually narrow down the cause I would:
- use ping as mentioned in the thread
- check whether the timeout you have set on the Tomcat connector is
roughly the same as used by mod_proxy_ajp
- check whether it looks like happening mostly for the same URL, then it
is more likely a servlet issue
- if it happens often enough sniff the traffic between Apache and Tomcat
and then check the packet details for one of the broken requests. For
this to work you might need to move Tomcat away from localhost.
Regards,
Rainer
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