Running Apache 2.2.4 on Windows 2003 server, I have two problems with an external filter written in C. The Apache server is running as a reverse proxy.
1) The filter is often called with no data passed to it and _eof(stdin) indicates the end of file. I inserted a debug statement in mod_ext_filter that shows prior to the filter being called, no data is read from the bucket, so nothing is piped into stdin for the filter to read. Yet, after the external filter exits, the client receives the entity body which is hundreds or thousands of bytes long. One possible clue, a mod_ext_filter debug statement reports a content-type of 'unspecified' when calling the external filter, however the HTTP response has a content-type of text/plain when the received by the client. The external filter does not modify the content or content-type. And more strange, if the response from the origin server is slow (a few seconds), the entity body DOES get passed to the external filter. 2) When receiving a response with large entity body, such as a 500 KB jpg, the filter gets passed the first 7746 bytes and nothing else. The client receives the full response. The Apache documentation refers to a 'standard Unix filter model', but I am unable to find an example of any Unix filter, let alone a well-behaved one. My filter reads from stdin, examines the data, then writes them to stdout. It seems to function correctly for the most part, but I sure would like to compare it to another, well-tested external filter. I've spent many days trying to get around these problems by disabling chunking, forcing the proxy to use HTTP 1.0, recoding my I/O processing multiple times, etc., all to no avail. Could someone shed some light on these problems? I need to get this filter working very soon. Thanks, Mark Zetts
