[elastic-agent] proxy requests to subprocesses to their metrics endpoints

x-pack/elastic-agent/pkg/core/monitoring/server/process.go

@@ -67,8 +67,14 @@ func processHandler(statsHandler func(http.ResponseWriter, *http.Request) error)
 			// proxy stats for elastic agent process
 			return statsHandler(w, r)
 		}
+		// TODO: allowlist of accepted endpoints to proxy to?
+		beatsEndpoint := vars["beatsEndpoint"]
 
-		metricsBytes, statusCode, metricsErr := processMetrics(r.Context(), id)
+		endpoint, err := generateEndpoint(id)
+		if err != nil {
+			return err
+		}
+		metricsBytes, statusCode, metricsErr := processMetrics(r.Context(), endpoint, beatsEndpoint)
 		if metricsErr != nil {
 			return metricsErr
 		}
@@ -82,23 +88,8 @@ func processHandler(statsHandler func(http.ResponseWriter, *http.Request) error)
 	}
 }
 
-func processMetrics(ctx context.Context, id string) ([]byte, int, error) {
-	detail, err := parseID(id)
-	if err != nil {
-		return nil, 0, err
-	}
-
-	endpoint := beats.MonitoringEndpoint(detail.spec, artifact.DefaultConfig().OS(), detail.output)
-	if !strings.HasPrefix(endpoint, httpPlusPrefix) && !strings.HasPrefix(endpoint, "http") {
-		// add prefix for npipe and unix
-		endpoint = httpPlusPrefix + endpoint
-	}
-
-	if detail.isMonitoring {
-		endpoint += "_monitor"
-	}
-
-	hostData, err := parse.ParseURL(endpoint, "http", "", "", "stats", "")
+func processMetrics(ctx context.Context, endpoint, path string) ([]byte, int, error) {
+	hostData, err := parse.ParseURL(endpoint, "http", "", "", path, "")
 	if err != nil {
 		return nil, 0, errorWithStatus(http.StatusInternalServerError, err)
 	}
@@ -145,6 +136,24 @@ func processMetrics(ctx context.Context, id string) ([]byte, int, error) {
 	return rb, resp.StatusCode, nil
 }
 
+func generateEndpoint(id string) (string, error) {
+	detail, err := parseID(id)
+	if err != nil {
+		return "", err
+	}
+
+	endpoint := beats.MonitoringEndpoint(detail.spec, artifact.DefaultConfig().OS(), detail.output)
+	if !strings.HasPrefix(endpoint, httpPlusPrefix) && !strings.HasPrefix(endpoint, "http") {
+		// add prefix for npipe and unix
+		endpoint = httpPlusPrefix + endpoint
+	}
+
+	if detail.isMonitoring {
+		endpoint += "_monitor"
+	}
+	return endpoint, nil
+}
+
 func writeResponse(w http.ResponseWriter, c interface{}) {
 	bytes, err := json.Marshal(c)
 	if err != nil {

x-pack/elastic-agent/pkg/core/monitoring/server/process_test.go

@@ -4,10 +4,15 @@
 package server
 
 import (
+	"context"
 	"errors"
+	"net"
 	"net/http"
+	"net/http/httptest"
+	"os"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -87,3 +92,29 @@ func TestStatusErr(t *testing.T) {
 		})
 	}
 }
+
+func TestProcessProxyRequest(t *testing.T) {
+	sock := "/tmp/elastic-agent-test.sock"
+	defer os.Remove(sock)
+
+	endpoint := "http+unix://" + sock
+	server := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Write the path to the client so they can verify the request
+		// was correct
+		w.Write([]byte(r.URL.Path))
+	}))
+
+	// Mimic subprocesses and listen on a unix socket
+	l, err := net.Listen("unix", sock)
+	require.NoError(t, err)
+	server.Listener = l
+	server.Start()
+	defer server.Close()
+
+	for _, path := range []string{"/stats", "/", "/state"} {
+		respBytes, _, err := processMetrics(context.Background(), endpoint, path)
+		require.NoError(t, err)
+		// Verify that the server saw the path we tried to request
+		assert.Equal(t, path, string(respBytes))
+	}
+}

x-pack/elastic-agent/pkg/core/monitoring/server/server.go

@@ -50,6 +50,8 @@ func exposeMetricsEndpoint(log *logger.Logger, config *common.Config, ns func(st
 	if enableProcessStats {
 		r.HandleFunc("/processes", processesHandler(routesFetchFn))
 		r.Handle("/processes/{processID}", createHandler(processHandler(statsHandler)))
+		r.Handle("/processes/{processID}/", createHandler(processHandler(statsHandler)))
+		r.Handle("/processes/{processID}/{beatsEndpoint}", createHandler(processHandler(statsHandler)))
 	}
 
 	mux := http.NewServeMux()