Am 25.10.2009 um 19:36 schrieb André Warnier:
Rolf Schaufelberger wrote:
Am 24.10.2009 um 12:13 schrieb André Warnier:
Rolf Schaufelberger wrote:
It always has googleads as referer with a very long refer string
and what das the 502 status mean?
http://lmgtfy.com?q=http+status+502
Ok, I can read what's written there, but what does it mean ?
I still have no idea, what leads to that error. As far as I
understood this, my backend server send something else but no HTTP
message to the frontend server.
But why?
Rolf,
502 Bad Gateway
The server was acting as a gateway or proxy and received an
invalid response from the downstream server.
It means that your front-end server received this request ("GET /"),
from some client, which apparently was at the time displaying a page
which itself had been obtained from the long link that you see in
the message. (It does not mean that the request itself came from a
Google server; it just means that on some page of Google somewhere,
there is a link that points to your site, and that someone clicked
on it).
Now, we don't know what the configuration of your front-end and back-
end servers are, nor what is exactly proxied to your back-end server
when the front-end server receives a request for "/".
But the error code 502 that is in the log (see description above)
seems to indicate that your front-end server passed this request
somehow to a back-end server, and that it received an invalid
response from the back-end server.
Why that is, is also not known to us, and quite impossible to figure
out with the information you provided.
So far I agree, and a request to / is just normal and handed over
to the backend server.
If I had to make a guess, I would say that the problem has nothing
to do with this request in particular, and that your front-end
server is just configured with too many children or threads,
compared to the physical memory it really has. So when many
requests come in and it tries to fork more children/threads to
handle them, it runs out of memory.
Reducing MaxClients may be a first option.
I've already dona this, the MaxClients for the backend ist set to 10
and there is not much traffic on that server. I had another server
running with 200 frontend and 30 backendserver with much less RAM.
Actually I don't even know for sure, if apache is causing these
problems, It's just the only thing running there,( tha database runs
on another server).
I' just desperately searching for anything that couses thtes problems.
About reproducing this access with LWP, sure :
lwp-request -m GET http://your-server-name/
but that is not going to tell you much.
Of course, but what I meant was, can I tell LWP to pass the same
referer string I found in my logfile, to simultate exactly that
request ?
Rolf Schaufelberger
