Skip config check in autodiscover for duplicated configurations (#29048)

If the configuration is already running, it has been already checked,
don't try to check it again to avoid problems with configuration checks
that fail if some resource already exist with the same identifiers.

(cherry picked from commit 1207d63)

CHANGELOG.next.asciidoc

@@ -153,6 +153,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix discovery of Nomad allocations with multiple events during startup. {pull}28700[28700]
 - Fix `fingerprint` processor to give it access to the `@timestamp` field. {issue}28683[28683]
 - Fix the wrong beat name on monitoring and state endpoint {issue}27755[27755]
+- Skip configuration checks in autodiscover for configurations that are already running {pull}29048[29048]
 
 *Auditbeat*
 

libbeat/autodiscover/autodiscover.go

@@ -64,6 +64,10 @@ type Autodiscover struct {
 	meta            *meta.Map
 	listener        bus.Listener
 	logger          *logp.Logger
+
+	// workDone is a channel used for testing purpouses, to know when the worker has
+	// done some work.
+	workDone chan struct{}
 }
 
 // NewAutodiscover instantiates and returns a new Autodiscover manager
@@ -165,6 +169,11 @@ func (a *Autodiscover) worker() {
 			// reset updated status
 			updated = false
 		}
+
+		// For testing purpouses.
+		if a.workDone != nil {
+			a.workDone <- struct{}{}
+		}
 	}
 }
 
@@ -207,26 +216,30 @@ func (a *Autodiscover) handleStart(event bus.Event) bool {
 			continue
 		}
 
-		err = a.factory.CheckConfig(config)
-		if err != nil {
-			a.logger.Error(errors.Wrap(err, fmt.Sprintf(
-				"Auto discover config check failed for config '%s', won't start runner",
-				common.DebugString(config, true))))
-			continue
-		}
-
 		// Update meta no matter what
 		dynFields := a.meta.Store(hash, meta)
 
+		if _, ok := newCfg[hash]; ok {
+			a.logger.Debugf("Config %v duplicated in start event", common.DebugString(config, true))
+			continue
+		}
+
 		if cfg, ok := a.configs[eventID][hash]; ok {
 			a.logger.Debugf("Config %v is already running", common.DebugString(config, true))
 			newCfg[hash] = cfg
 			continue
-		} else {
-			newCfg[hash] = &reload.ConfigWithMeta{
-				Config: config,
-				Meta:   &dynFields,
-			}
+		}
+
+		err = a.factory.CheckConfig(config)
+		if err != nil {
+			a.logger.Error(errors.Wrap(err, fmt.Sprintf(
+				"Auto discover config check failed for config '%s', won't start runner",
+				common.DebugString(config, true))))
+			continue
+		}
+		newCfg[hash] = &reload.ConfigWithMeta{
+			Config: config,
+			Meta:   &dynFields,
 		}
 
 		updated = true

libbeat/autodiscover/autodiscover_test.go

@@ -75,6 +75,8 @@ type mockAdapter struct {
 	mutex   sync.Mutex
 	configs []*common.Config
 	runners []*mockRunner
+
+	CheckConfigCallCount int
 }
 
 // CreateConfig generates a valid list of configs from the given event, the received event will have all keys defined by `StartFilter`
@@ -87,6 +89,8 @@ func (m *mockAdapter) CreateConfig(event bus.Event) ([]*common.Config, error) {
 
 // CheckConfig tests given config to check if it will work or not, returns errors in case it won't work
 func (m *mockAdapter) CheckConfig(c *common.Config) error {
+	m.CheckConfigCallCount++
+
 	config := struct {
 		Broken bool `config:"broken"`
 	}{}
@@ -324,6 +328,66 @@ func TestAutodiscoverHash(t *testing.T) {
 	assert.False(t, runners[1].stopped)
 }
 
+func TestAutodiscoverDuplicatedConfigConfigCheckCalledOnce(t *testing.T) {
+	goroutines := resources.NewGoroutinesChecker()
+	defer goroutines.Check(t)
+
+	// Register mock autodiscover provider
+	busChan := make(chan bus.Bus, 1)
+
+	Registry = NewRegistry()
+	Registry.AddProvider("mock", func(beatName string, b bus.Bus, uuid uuid.UUID, c *common.Config, k keystore.Keystore) (Provider, error) {
+		// intercept bus to mock events
+		busChan <- b
+
+		return &mockProvider{}, nil
+	})
+
+	// Create a mock adapter that returns a duplicated config
+	runnerConfig, _ := common.NewConfigFrom(map[string]string{
+		"id": "foo",
+	})
+	adapter := mockAdapter{
+		configs: []*common.Config{runnerConfig, runnerConfig},
+	}
+
+	// and settings:
+	providerConfig, _ := common.NewConfigFrom(map[string]string{
+		"type": "mock",
+	})
+	config := Config{
+		Providers: []*common.Config{providerConfig},
+	}
+	k, _ := keystore.NewFileKeystore("test")
+	// Create autodiscover manager
+	autodiscover, err := NewAutodiscover("test", nil, &adapter, &adapter, &config, k)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	autodiscover.workDone = make(chan struct{})
+
+	// Start it
+	autodiscover.Start()
+	defer autodiscover.Stop()
+	eventBus := <-busChan
+
+	// Publish a couple of events.
+	for i := 0; i < 2; i++ {
+		eventBus.Publish(bus.Event{
+			"id":       "foo",
+			"provider": "mock",
+			"start":    true,
+			"meta": common.MapStr{
+				"foo": "bar",
+			},
+		})
+		<-autodiscover.workDone
+		assert.Equal(t, 1, len(adapter.Runners()), "Only one runner should be started")
+		assert.Equal(t, 1, adapter.CheckConfigCallCount, "Check config should have been called only once")
+	}
+}
+
 func TestAutodiscoverWithConfigCheckFailures(t *testing.T) {
 	goroutines := resources.NewGoroutinesChecker()
 	defer goroutines.Check(t)