Fixed Content-Length deletion for reverse proxies in Martini #17
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It turns out that deleting Content-Length header field at the end of serveGzip function may not be enough for gzip. According to the spec of compress/gzip, a Write() call may flush the writer before closing it. This means that in certain cases, gzip writer flushes compressed data to the underlying martini.ResponseWriter with a wrong header Content-Length field, i.e before it is deleted by serveGzip resulting in a "Conn.Write wrote more than the declared Content-Length" error. This change adds a defensive measure of deleting Content-Length before a potential write.
| @@ -88,7 +88,9 @@ func (grw gzipResponseWriter) Write(p []byte) (int, error) { | |||
| if len(grw.Header().Get(HeaderContentType)) == 0 { | |||
| grw.Header().Set(HeaderContentType, http.DetectContentType(p)) | |||
| } | |||
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| // removing content length before writing in case gzip.Writer writes to the | |||
| // underlying http.ResponseWriter before closing. See notes in compress/gzip. | |||
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Here is the link to compress/gzip.
Extracted comment:
Write writes a compressed form of p to the underlying io.Writer. The compressed bytes are not necessarily flushed until the Writer is closed.
In some cases, WriteHeader() can be called explicitly by the user which may result in the Content-Length field of a header to be written to the underlying ResponseWriter. This CL adds one more defensive removal of Content-Length for the reverse proxy issue.
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It turns out that deleting Content-Length header field at the end of
serveGzip function may not be enough for gzip. According to the spec
of compress/gzip, a Write() call may flush the writer before closing
it. This means that in certain cases, gzip writer flushes compressed
data to the underlying martini.ResponseWriter with a wrong header
Content-Length field, i.e before it is deleted by serveGzip resulting
in a "Conn.Write wrote more than the declared Content-Length" error.
This change adds a defensive measure of deleting Content-Length
before a potential write.