Revert "refactoring prometheus endpoint"

This reverts commit 2f852e9.

command/agent/http.go

@@ -15,6 +15,8 @@ import (
 	"github.com/NYTimes/gziphandler"
 	"github.com/hashicorp/nomad/helper/tlsutil"
 	"github.com/hashicorp/nomad/nomad/structs"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/ugorji/go/codec"
 )
 
@@ -83,6 +85,12 @@ func NewHTTPServer(agent *Agent, config *Config) (*HTTPServer, error) {
 	// Handle requests with gzip compression
 	go http.Serve(ln, gziphandler.GzipHandler(mux))
 
+	// Register Prometheus separately as this requires uncompressed responses
+	srv.registerPrometheusHandler()
+
+	// Handle requests without gzip compression
+	go http.Serve(ln, mux)
+
 	return srv, nil
 }
 
@@ -105,6 +113,12 @@ func newScadaHttp(agent *Agent, list net.Listener) *HTTPServer {
 	// Handle requests with gzip compression
 	go http.Serve(list, gziphandler.GzipHandler(mux))
 
+	// Register Prometheus separately as this requires uncompressed responses
+	srv.registerPrometheusHandler()
+
+	// Handle requests without gzip compression
+	go http.Serve(list, mux)
+
 	return srv
 }
 
@@ -133,6 +147,19 @@ func (s *HTTPServer) Shutdown() {
 	}
 }
 
+// Create a prometheus handler and register it separately, as other requests
+// use gzip compression
+func (s *HTTPServer) registerPrometheusHandler() {
+	handlerOptions := promhttp.HandlerOpts{
+		ErrorLog:           s.logger,
+		ErrorHandling:      promhttp.ContinueOnError,
+		DisableCompression: true,
+	}
+
+	handler := promhttp.HandlerFor(prometheus.DefaultGatherer, handlerOptions)
+	s.mux.Handle("/metrics", handler)
+}
+
 // registerHandlers is used to attach our handlers to the mux
 func (s *HTTPServer) registerHandlers(enableDebug bool) {
 	s.mux.HandleFunc("/v1/jobs", s.wrap(s.JobsRequest))

command/agent/metrics_endpoint.go

@@ -2,29 +2,13 @@ package agent
 
 import (
 	"net/http"
-
-	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 // MetricsRequest returns metrics for the agent. Metrics are JSON by default
 // but Prometheus is an optional format.
 func (s *HTTPServer) MetricsRequest(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
-	if req.Method != "GET" {
-		return nil, CodedError(405, ErrInvalidMethod)
+	if req.Method == "GET" {
+		return s.agent.InmemSink.DisplayMetrics(resp, req)
 	}
-
-	if format := req.URL.Query().Get("format"); format == "prometheus" {
-		handlerOptions := promhttp.HandlerOpts{
-			ErrorLog:           s.logger,
-			ErrorHandling:      promhttp.ContinueOnError,
-			DisableCompression: true,
-		}
-
-		handler := promhttp.HandlerFor(prometheus.DefaultGatherer, handlerOptions)
-		handler.ServeHTTP(resp, req)
-		return nil, nil
-	}
-
-	return s.agent.InmemSink.DisplayMetrics(resp, req)
+	return nil, CodedError(405, ErrInvalidMethod)
 }