net/http: no way for Server to set Trailer headers #7759
Labels
Milestone
Comments
wking
added a commit
to ipfs/kubo
that referenced
this issue
Jun 24, 2015
For streaming responses (e.g. 'ipfs add -r /path/to/root/directory'), we may hit errors later on in the stream, after we've already written the initial 200 response and started in on the streaming body (e.g. /path/to/root/directory/a/b/c is an unsupported file type). We should check for that sort of error, and set a trailer [1] if there were any errors. Unfortunately, it's a bit awkward to set these headers in Go 1.4 and earlier [2], but [2] does have a workaround for Go 1.4 (it's not clear if the workaround is compatible with Go 1.3). [1]: http://tools.ietf.org/html/rfc2616#section-14.40 [2]: golang/go#7759 License: MIT Signed-off-by: W. Trevor King <wking@tremily.us>
wking
added a commit
to ipfs/kubo
that referenced
this issue
Jun 24, 2015
For streaming responses (e.g. 'ipfs add -r /path/to/root/directory'), we may hit errors later on in the stream, after we've already written the initial 200 response and started in on the streaming body (e.g. /path/to/root/directory/a/b/c is an unsupported file type). We should check for that sort of error, and set a trailer [1] if there were any errors. Unfortunately, it's a bit awkward to set these headers in Go 1.4 and earlier [2], but [2] does have a workaround for Go 1.4 (it's not clear if the workaround is compatible with Go 1.3). [1]: http://tools.ietf.org/html/rfc2616#section-14.40 [2]: golang/go#7759 License: MIT Signed-off-by: W. Trevor King <wking@tremily.us>
wking
added a commit
to ipfs/kubo
that referenced
this issue
Jun 24, 2015
For streaming responses (e.g. 'ipfs add -r /path/to/root/directory'), we may hit errors later on in the stream, after we've already written the initial 200 response and started in on the streaming body (e.g. /path/to/root/directory/a/b/c is an unsupported file type). We should check for that sort of error, and set a trailer [1] if there were any errors. Unfortunately, it's a bit awkward to set these headers in Go 1.4 and earlier [2], but [2] does have a workaround for Go 1.4 (it's not clear if the workaround is compatible with Go 1.3). [1]: http://tools.ietf.org/html/rfc2616#section-14.40 [2]: golang/go#7759 License: MIT Signed-off-by: W. Trevor King <wking@tremily.us>
wking
added a commit
to ipfs/kubo
that referenced
this issue
Jun 24, 2015
For streaming responses (e.g. 'ipfs add -r /path/to/root/directory'), we may hit errors later on in the stream, after we've already written the initial 200 response and started in on the streaming body (e.g. /path/to/root/directory/a/b/c is an unsupported file type). We should check for that sort of error, and set a trailer [1] if there were any errors. Unfortunately, it's a bit awkward to set these headers in Go 1.4 and earlier [2], but [2] does have a workaround for Go 1.4 (it's not clear if the workaround is compatible with Go 1.3). [1]: http://tools.ietf.org/html/rfc2616#section-14.40 [2]: golang/go#7759 License: MIT Signed-off-by: W. Trevor King <wking@tremily.us>
|
Does this mean the example at http://golang.org/pkg/net/http/#example_ResponseWriter_trailers does not actually work? |
|
@drcrallen, what gives you that impression? See the most recent comment. https://go-review.googlesource.com/2157 added support. It's in Go 1.5. |
|
@bradfitz Misreading of docs on my part. Found out I have 1.4.2 installed but was using tutorials from prior URL, which are built for go1.5 (in the page footer which I missed). My bad |
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
There's no way for Server handlers to set Trailer headers. From a test I just wrote, with a work-around and TODO for Go 1.4: ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) { w.Header().Set("Connection", "close") w.Header().Set("Trailer", "Server-Trailer-A, Server-Trailer-B") w.Header().Add("Trailer", "Server-Trailer-C") var decl []string for k := range r.Trailer { decl = append(decl, k) } sort.Strings(decl) slurp, err := ioutil.ReadAll(r.Body) if err != nil { t.Errorf("Server reading request body: %v", err) } if string(slurp) != "foo" { t.Errorf("Server read request body %q; want foo", slurp) } if r.Trailer == nil { io.WriteString(w, "nil Trailer") } else { fmt.Fprintf(w, "decl: %v, vals: %s, %s", decl, r.Trailer.Get("Client-Trailer-A"), r.Trailer.Get("Client-Trailer-B")) } // TODO: There's no way yet for the server to set trailers // without hijacking, so do that for now, just to test the client. // Later, in Go 1.4, it should be be implicit that any mutations // to w.Header() after the initial write are the trailers to be // sent, if and only if they were previously declared with // w.Header().Set("Trailer", ..keys..) w.(Flusher).Flush() conn, buf, _ := w.(Hijacker).Hijack() t := Header{} t.Set("Server-Trailer-A", "valuea") t.Set("Server-Trailer-C", "valuec") // skipping B buf.WriteString("0\r\n") // eof t.Write(buf) buf.WriteString("\r\n") // end of trailers buf.Flush() conn.Close()The text was updated successfully, but these errors were encountered: