Update client_golang to fix promhttp error handling (#6986)

Fixes #6139

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

go.mod

@@ -33,7 +33,7 @@ require (
 	github.com/opentracing/opentracing-go v1.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/alertmanager v0.20.0
-	github.com/prometheus/client_golang v1.5.0
+	github.com/prometheus/client_golang v1.5.1
 	github.com/prometheus/client_model v0.2.0
 	github.com/prometheus/common v0.9.1
 	github.com/samuel/go-zookeeper v0.0.0-20190923202752-2cc03de413da

go.sum

@@ -459,8 +459,8 @@ github.com/prometheus/client_golang v0.9.3-0.20190127221311-3c4408c8b829/go.mod
 github.com/prometheus/client_golang v1.0.0/go.mod h1:db9x61etRT2tGnBNRi70OPL5FsnadC4Ky3P0J6CfImo=
 github.com/prometheus/client_golang v1.2.1/go.mod h1:XMU6Z2MjaRKVu/dC1qupJI9SiNkDYzz3xecMgSW/F+U=
 github.com/prometheus/client_golang v1.3.0/go.mod h1:hJaj2vgQTGQmVCsAACORcieXFeDPbaTKGT+JTgUa3og=
-github.com/prometheus/client_golang v1.5.0 h1:Ctq0iGpCmr3jeP77kbF2UxgvRwzWWz+4Bh9/vJTyg1A=
+github.com/prometheus/client_golang v1.5.1 h1:bdHYieyGlH+6OLEk2YQha8THib30KP0/yD0YH9m6xcA=
-github.com/prometheus/client_golang v1.5.0/go.mod h1:e9GMxYsXl05ICDXkRhurwBS4Q3OK1iX/F2sw+iXX5zU=
+github.com/prometheus/client_golang v1.5.1/go.mod h1:e9GMxYsXl05ICDXkRhurwBS4Q3OK1iX/F2sw+iXX5zU=
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
 github.com/prometheus/client_model v0.0.0-20190115171406-56726106282f/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
 github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=

vendor/github.com/prometheus/client_golang/prometheus/promhttp/delegator.go

@@ -53,12 +53,16 @@ func (r *responseWriterDelegator) Written() int64 {
 }
 
 func (r *responseWriterDelegator) WriteHeader(code int) {
+	if r.observeWriteHeader != nil && !r.wroteHeader {
+		// Only call observeWriteHeader for the 1st time. It's a bug if
+		// WriteHeader is called more than once, but we want to protect
+		// against it here. Note that we still delegate the WriteHeader
+		// to the original ResponseWriter to not mask the bug from it.
+		r.observeWriteHeader(code)
+	}
 	r.status = code
 	r.wroteHeader = true
 	r.ResponseWriter.WriteHeader(code)
-	if r.observeWriteHeader != nil {
-		r.observeWriteHeader(code)
-	}
 }
 
 func (r *responseWriterDelegator) Write(b []byte) (int, error) {

vendor/github.com/prometheus/client_golang/prometheus/promhttp/http.go

@@ -167,15 +167,12 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
 
 		enc := expfmt.NewEncoder(w, contentType)
 
-		var lastErr error
-
 		// handleError handles the error according to opts.ErrorHandling
 		// and returns true if we have to abort after the handling.
 		handleError := func(err error) bool {
 			if err == nil {
 				return false
 			}
-			lastErr = err
 			if opts.ErrorLog != nil {
 				opts.ErrorLog.Println("error encoding and sending metric family:", err)
 			}
@@ -184,7 +181,10 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
 			case PanicOnError:
 				panic(err)
 			case HTTPErrorOnError:
-				httpError(rsp, err)
+				// We cannot really send an HTTP error at this
+				// point because we most likely have written
+				// something to rsp already. But at least we can
+				// stop sending.
 				return true
 			}
 			// Do nothing in all other cases, including ContinueOnError.
@@ -202,10 +202,6 @@ func HandlerFor(reg prometheus.Gatherer, opts HandlerOpts) http.Handler {
 				return
 			}
 		}
-
-		if lastErr != nil {
-			httpError(rsp, lastErr)
-		}
 	})
 
 	if opts.Timeout <= 0 {
@@ -276,7 +272,12 @@ type HandlerErrorHandling int
 // errors are encountered.
 const (
 	// Serve an HTTP status code 500 upon the first error
-	// encountered. Report the error message in the body.
+	// encountered. Report the error message in the body. Note that HTTP
+	// errors cannot be served anymore once the beginning of a regular
+	// payload has been sent. Thus, in the (unlikely) case that encoding the
+	// payload into the negotiated wire format fails, serving the response
+	// will simply be aborted. Set an ErrorLog in HandlerOpts to detect
+	// those errors.
 	HTTPErrorOnError HandlerErrorHandling = iota
 	// Ignore errors and try to serve as many metrics as possible.  However,
 	// if no metrics can be served, serve an HTTP status code 500 and the
@@ -365,11 +366,9 @@ func gzipAccepted(header http.Header) bool {
 }
 
 // httpError removes any content-encoding header and then calls http.Error with
-// the provided error and http.StatusInternalServerErrer. Error contents is
+// the provided error and http.StatusInternalServerError. Error contents is
-// supposed to be uncompressed plain text. However, same as with a plain
+// supposed to be uncompressed plain text. Same as with a plain http.Error, this
-// http.Error, any header settings will be void if the header has already been
+// must not be called if the header or any payload has already been sent.
-// sent. The error message will still be written to the writer, but it will
-// probably be of limited use.
 func httpError(rsp http.ResponseWriter, err error) {
 	rsp.Header().Del(contentEncodingHeader)
 	http.Error(

vendor/modules.txt

@@ -272,7 +272,7 @@ github.com/opentracing/opentracing-go/log
 github.com/pkg/errors
 # github.com/prometheus/alertmanager v0.20.0
 github.com/prometheus/alertmanager/api/v2/models
-# github.com/prometheus/client_golang v1.5.0
+# github.com/prometheus/client_golang v1.5.1
 github.com/prometheus/client_golang/api
 github.com/prometheus/client_golang/api/prometheus/v1
 github.com/prometheus/client_golang/prometheus