15370: Fix flaky test.

[arvados.git] / sdk / go / httpserver / responsewriter.go

diff --git a/sdk/go/httpserver/responsewriter.go b/sdk/go/httpserver/responsewriter.go
index d37822ffe3e5cd0f582a59a3ee45b1d322fed4ac..049a3f1aae184de0ef522656741494db42764802 100644 (file)
--- a/sdk/go/httpserver/responsewriter.go
+++ b/sdk/go/httpserver/responsewriter.go
@@ -8,10 +8,13 @@ import (
        "net/http"
 )
 
+const sniffBytes = 1024
+
 type ResponseWriter interface {
        http.ResponseWriter
        WroteStatus() int
        WroteBodyBytes() int
+       Sniffed() []byte
 }
 
 // responseWriter wraps http.ResponseWriter and exposes the status
@@ -19,9 +22,10 @@ type ResponseWriter interface {
 // error.
 type responseWriter struct {
        http.ResponseWriter
-       wroteStatus    int   // Last status given to WriteHeader()
+       wroteStatus    int   // First status given to WriteHeader()
        wroteBodyBytes int   // Bytes successfully written
        err            error // Last error returned from Write()
+       sniffed        []byte
 }
 
 func WrapResponseWriter(orig http.ResponseWriter) ResponseWriter {
@@ -36,11 +40,21 @@ func (w *responseWriter) CloseNotify() <-chan bool {
 }
 
 func (w *responseWriter) WriteHeader(s int) {
-       w.wroteStatus = s
+       if w.wroteStatus == 0 {
+               w.wroteStatus = s
+       }
+       // ...else it's too late to change the status seen by the
+       // client -- but we call the wrapped WriteHeader() anyway so
+       // it can log a warning.
        w.ResponseWriter.WriteHeader(s)
 }
 
 func (w *responseWriter) Write(data []byte) (n int, err error) {
+       if w.wroteStatus == 0 {
+               w.WriteHeader(http.StatusOK)
+       } else if w.wroteStatus >= 400 {
+               w.sniff(data)
+       }
        n, err = w.ResponseWriter.Write(data)
        w.wroteBodyBytes += n
        w.err = err
@@ -58,3 +72,17 @@ func (w *responseWriter) WroteBodyBytes() int {
 func (w *responseWriter) Err() error {
        return w.err
 }
+
+func (w *responseWriter) sniff(data []byte) {
+       max := sniffBytes - len(w.sniffed)
+       if max <= 0 {
+               return
+       } else if max < len(data) {
+               data = data[:max]
+       }
+       w.sniffed = append(w.sniffed, data...)
+}
+
+func (w *responseWriter) Sniffed() []byte {
+       return w.sniffed
+}