more ut

internal/pkg/agent/application/monitoring/reload/reload.go

@@ -49,6 +49,11 @@ func (sr *ServerReloader) Start() {
 }
 
 func (sr *ServerReloader) start() {
+	if sr.s != nil && sr.isServerRunning {
+		// server is already running
+		return
+	}
+
 	sr.log.Info("Starting server")
 	var err error
 	sr.s, err = sr.newServerFn()
@@ -70,6 +75,10 @@ func (sr *ServerReloader) Stop() error {
 }
 
 func (sr *ServerReloader) stop() error {
+	if sr.s == nil {
+		// stopping not started server
+		return nil
+	}
 	sr.log.Info("Stopping server")
 
 	sr.isServerRunning = false

internal/pkg/agent/application/monitoring/reload/reload_test.go

@@ -0,0 +1,129 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package reload
+
+import (
+	"testing"
+
+	aConfig "github.com/elastic/elastic-agent/internal/pkg/config"
+	monitoringCfg "github.com/elastic/elastic-agent/internal/pkg/core/monitoring/config"
+	"github.com/elastic/elastic-agent/pkg/core/logger"
+	"github.com/stretchr/testify/require"
+)
+
+func TestReload(t *testing.T) {
+	tcs := []struct {
+		name        string
+		currEnabled bool
+		currMetrics bool
+		currRunning bool
+
+		newConfig       string
+		expectedRunning bool
+		expectedStart   bool
+		expectedStop    bool
+	}{
+		{
+			"start with default config",
+			false, false, false,
+			``,
+			true, true, false,
+		},
+		{
+			"start when not running, monitoring enabled",
+			false, false, false,
+			`
+agent.monitoring.enabled: true
+`,
+			true, true, false,
+		},
+		{
+			"do not start when not running, only metrics enabled",
+			false, false, false,
+			`
+agent.monitoring.enabled: false
+agent.monitoring.metrics: true
+`,
+			false, false, false,
+		},
+
+		{
+			"stop when running, monitoring disabled",
+			true, true, true,
+			`
+agent.monitoring.enabled: false
+`,
+			false, false, true,
+		},
+		{
+			"stop when running, monitoring.metrics disabled",
+			true, true, true,
+			`
+agent.monitoring.metrics: false
+`,
+			false, false, true,
+		},
+		{
+			"stop stopped server",
+			false, false, false,
+			`
+agent.monitoring.metrics: false
+`,
+			false, false, false,
+		},
+		{
+			"start started server",
+			true, true, true,
+			`
+agent.monitoring.enabled: true
+`,
+			true, false, false,
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.name, func(t *testing.T) {
+			fsc := &fakeServerController{}
+			log, _ := logger.NewTesting(tc.name)
+			cfg := &monitoringCfg.MonitoringConfig{
+				Enabled:        tc.currEnabled,
+				MonitorMetrics: tc.currMetrics,
+			}
+			r := NewServerReloader(
+				func() (ServerController, error) {
+					return fsc, nil
+				},
+				log,
+				cfg,
+			)
+			r.isServerRunning = tc.currRunning
+			if tc.currRunning {
+				r.s = fsc
+			}
+
+			newCfg := aConfig.MustNewConfigFrom(tc.newConfig)
+			require.NoError(t, r.Reload(newCfg))
+
+			require.Equal(t, tc.expectedRunning, r.isServerRunning)
+			require.Equal(t, tc.expectedStart, fsc.startTriggered)
+			require.Equal(t, tc.expectedStop, fsc.stopTriggered)
+		})
+	}
+}
+
+type fakeServerController struct {
+	startTriggered bool
+	stopTriggered  bool
+}
+
+func (fsc *fakeServerController) Start() { fsc.startTriggered = true }
+func (fsc *fakeServerController) Stop() error {
+	fsc.stopTriggered = true
+	return nil
+}
+func (fsc *fakeServerController) Reset() {
+	fsc.startTriggered = false
+	fsc.stopTriggered = false
+}