Fix logstash output panic without hosts

CHANGELOG.asciidoc

@@ -37,8 +37,8 @@ https://github.com/elastic/beats/compare/v5.0.0-alpha5...master[Check the HEAD d
 
 *Affecting all Beats*
 - Fix Elasticsearch structured error response parsing error. {issue}2229[2229]
-
 - Fixed the run script to allow the overriding of the configuration file. {issue}2171[2171]
+- Fix logstash output crash if no hosts are configured. {issue}2325[2325]
 
 *Metricbeat*
 - Fix module filters to work properly with drop_event filter. {issue}2249[2249]

libbeat/outputs/elasticsearch/output.go

@@ -132,8 +132,13 @@ func (out *elasticsearchOutput) init(
 
 	out.clients = clients
 	loadBalance := config.LoadBalance
-	m, err := modeutil.NewConnectionMode(clients, !loadBalance,
-		maxAttempts, waitRetry, config.Timeout, maxWaitRetry)
+	m, err := modeutil.NewConnectionMode(clients, modeutil.Settings{
+		Failover:     !loadBalance,
+		MaxAttempts:  maxAttempts,
+		Timeout:      config.Timeout,
+		WaitRetry:    waitRetry,
+		MaxWaitRetry: maxWaitRetry,
+	})
 	if err != nil {
 		return err
 	}

libbeat/outputs/kafka/kafka.go

@@ -143,13 +143,13 @@ func (k *kafka) initMode(guaranteed bool) (mode.ConnectionMode, error) {
 		maxAttempts = 0
 	}
 
-	mode, err := modeutil.NewAsyncConnectionMode(
-		clients,
-		false,
-		maxAttempts,
-		defaultWaitRetry,
-		libCfg.Net.WriteTimeout,
-		defaultMaxWaitRetry)
+	mode, err := modeutil.NewAsyncConnectionMode(clients, modeutil.Settings{
+		Failover:     false,
+		MaxAttempts:  maxAttempts,
+		WaitRetry:    defaultWaitRetry,
+		Timeout:      libCfg.Net.WriteTimeout,
+		MaxWaitRetry: defaultMaxWaitRetry,
+	})
 	if err != nil {
 		logp.Err("Failed to configure kafka connection: %v", err)
 		return nil, err

libbeat/outputs/logstash/logstash.go

@@ -70,12 +70,6 @@ func (lj *logstash) init(cfg *common.Config) error {
 		return err
 	}
 
-	sendRetries := config.MaxRetries
-	maxAttempts := sendRetries + 1
-	if sendRetries < 0 {
-		maxAttempts = 0
-	}
-
 	tls, err := outputs.LoadTLSConfig(config.TLS)
 	if err != nil {
 		return err
@@ -93,22 +87,8 @@ func (lj *logstash) init(cfg *common.Config) error {
 		},
 	}
 
-	logp.Info("Max Retries set to: %v", sendRetries)
-	var m mode.ConnectionMode
-	if config.Pipelining == 0 {
-		clients, err := modeutil.MakeClients(cfg, makeClientFactory(&config, transp))
-		if err == nil {
-			m, err = modeutil.NewConnectionMode(clients, !config.LoadBalance,
-				maxAttempts, defaultWaitRetry, config.Timeout, defaultMaxWaitRetry)
-		}
-	} else {
-		clients, err := modeutil.MakeAsyncClients(cfg,
-			makeAsyncClientFactory(&config, transp))
-		if err == nil {
-			m, err = modeutil.NewAsyncConnectionMode(clients, !config.LoadBalance,
-				maxAttempts, defaultWaitRetry, config.Timeout, defaultMaxWaitRetry)
-		}
-	}
+	logp.Info("Max Retries set to: %v", config.MaxRetries)
+	m, err := initConnectionMode(cfg, &config, transp)
 	if err != nil {
 		return err
 	}
@@ -119,6 +99,40 @@ func (lj *logstash) init(cfg *common.Config) error {
 	return nil
 }
 
+func initConnectionMode(
+	cfg *common.Config,
+	config *logstashConfig,
+	transp *transport.Config,
+) (mode.ConnectionMode, error) {
+	sendRetries := config.MaxRetries
+	maxAttempts := sendRetries + 1
+	if sendRetries < 0 {
+		maxAttempts = 0
+	}
+
+	settings := modeutil.Settings{
+		Failover:     !config.LoadBalance,
+		MaxAttempts:  maxAttempts,
+		Timeout:      config.Timeout,
+		WaitRetry:    defaultWaitRetry,
+		MaxWaitRetry: defaultMaxWaitRetry,
+	}
+
+	if config.Pipelining == 0 {
+		clients, err := modeutil.MakeClients(cfg, makeClientFactory(config, transp))
+		if err != nil {
+			return nil, err
+		}
+		return modeutil.NewConnectionMode(clients, settings)
+	}
+
+	clients, err := modeutil.MakeAsyncClients(cfg, makeAsyncClientFactory(config, transp))
+	if err != nil {
+		return nil, err
+	}
+	return modeutil.NewAsyncConnectionMode(clients, settings)
+}
+
 func makeClientFactory(
 	cfg *logstashConfig,
 	tcfg *transport.Config,

libbeat/outputs/mode/modeutil/modeutil.go

@@ -13,32 +13,41 @@ type ClientFactory func(host string) (mode.ProtocolClient, error)
 
 type AsyncClientFactory func(string) (mode.AsyncProtocolClient, error)
 
+type Settings struct {
+	Failover     bool
+	MaxAttempts  int
+	WaitRetry    time.Duration
+	Timeout      time.Duration
+	MaxWaitRetry time.Duration
+}
+
 func NewConnectionMode(
 	clients []mode.ProtocolClient,
-	failover bool,
-	maxAttempts int,
-	waitRetry, timeout, maxWaitRetry time.Duration,
+	s Settings,
 ) (mode.ConnectionMode, error) {
-	if failover {
+	if s.Failover {
 		clients = NewFailoverClient(clients)
 	}
 
+	maxSend := s.MaxAttempts
+	wait := s.WaitRetry
+	maxWait := s.MaxWaitRetry
+	to := s.Timeout
+
 	if len(clients) == 1 {
-		return single.New(clients[0], maxAttempts, waitRetry, timeout, maxWaitRetry)
+		return single.New(clients[0], maxSend, wait, to, maxWait)
 	}
-	return lb.NewSync(clients, maxAttempts, waitRetry, timeout, maxWaitRetry)
+	return lb.NewSync(clients, maxSend, wait, to, maxWait)
 }
 
 func NewAsyncConnectionMode(
 	clients []mode.AsyncProtocolClient,
-	failover bool,
-	maxAttempts int,
-	waitRetry, timeout, maxWaitRetry time.Duration,
+	s Settings,
 ) (mode.ConnectionMode, error) {
-	if failover {
+	if s.Failover {
 		clients = NewAsyncFailoverClient(clients)
 	}
-	return lb.NewAsync(clients, maxAttempts, waitRetry, timeout, maxWaitRetry)
+	return lb.NewAsync(clients, s.MaxAttempts, s.WaitRetry, s.Timeout, s.MaxWaitRetry)
 }
 
 // MakeClients will create a list from of ProtocolClient instances from
@@ -99,8 +108,8 @@ func MakeAsyncClients(
 
 func ReadHostList(cfg *common.Config) ([]string, error) {
 	config := struct {
-		Hosts  []string `config:"hosts"`
-		Worker int      `config:"worker"`
+		Hosts  []string `config:"hosts"  validate:"required"`
+		Worker int      `config:"worker" validate:"min=1"`
 	}{
 		Worker: 1,
 	}

libbeat/outputs/mode/modeutil/modeutil_test.go

@@ -34,7 +34,7 @@ func makeTestClients(c map[string]interface{},
 func TestMakeEmptyClientFail(t *testing.T) {
 	config := map[string]interface{}{}
 	clients, err := makeTestClients(config, dummyMockClientFactory)
-	assert.Equal(t, mode.ErrNoHostsConfigured, err)
+	assert.Error(t, err)
 	assert.Equal(t, 0, len(clients))
 }
 

libbeat/outputs/redis/redis.go

@@ -131,8 +131,13 @@ func (r *redisOut) init(cfg *common.Config, expireTopo int) error {
 	}
 
 	logp.Info("Max Retries set to: %v", sendRetries)
-	m, err := modeutil.NewConnectionMode(clients, !config.LoadBalance,
-		maxAttempts, defaultWaitRetry, config.Timeout, defaultMaxWaitRetry)
+	m, err := modeutil.NewConnectionMode(clients, modeutil.Settings{
+		Failover:     !config.LoadBalance,
+		MaxAttempts:  maxAttempts,
+		Timeout:      config.Timeout,
+		WaitRetry:    defaultWaitRetry,
+		MaxWaitRetry: defaultMaxWaitRetry,
+	})
 	if err != nil {
 		return err
 	}