During today’s hacking aboot I came across the above error from our Solr query library. The error indicates that some part of Tomcat was unable to parse the “GET / HTTP/1.1″ string – where it is unable to determine the “HTTP/1.1″ part. A problem like this could be introduced by having a space in the query string (and it not being escaped properly), so that the request would have been for “GET /?a=b c HTTP/1.1″. After running through both the working and non-working query through ngrep and wireshark, this did however not seem to be the problem. My spaces were properly escaped using plus signs (GET /?a=b+c HTTP/1.1).

There does however seem to be a problem (at least with our version of Tomcat – 6.0.20) which results in the +-s being resolved before the request is handed off to the code that attempts to parse the header, so even though it is properly escaped using “+”, it still barfs.

The solution:

Use %20 to escape spaces instead of + signs; simply adding str_replace(” “, “%20″, ..); in our query layer solved the problem.