I have very strange problems with apache 2.4.18 mod_proxy on Debian Linux Testing with kernel 4.3.0 (amd64). I am using it as a forward proxy:
ProxyRequests On ProxyVia On ProxyBadHeader Ignore AllowCONNECT 1-65535
Right after starting the server, everything works. But after only a few requests, it stops serving requests:
Proxy Error The proxy server received an invalid response from an upstream server. The proxy server could not handle the request GET http://www.google.de/. Reason: DNS lookup failure for: www.google.de
If I try to add the host (in the example: www.google.de) to the /etc/hosts file, it does not change anything. Also, name resolving works normally on the server, no other service has any problems.
LogLevel trace8 shows nothing related to name resolving. It seems to me that this has actually nothing to do with DNS.
What is this? Thanks.