Consistently return ErrClosedClient when calling an exported function…

… on a closed client

client.go

@@ -144,7 +144,6 @@ func (client *client) Config() *Config {
 }
 
 func (client *client) Close() error {
-	// Check to see whether the client is closed
 	if client.Closed() {
 		// Chances are this is being called from a defer() and the error will go unobserved
 		// so we go ahead and log the event in this case.
@@ -177,7 +176,6 @@ func (client *client) Closed() bool {
 }
 
 func (client *client) Topics() ([]string, error) {
-	// Check to see whether the client is closed
 	if client.Closed() {
 		return nil, ErrClosedClient
 	}
@@ -194,7 +192,6 @@ func (client *client) Topics() ([]string, error) {
 }
 
 func (client *client) Partitions(topic string) ([]int32, error) {
-	// Check to see whether the client is closed
 	if client.Closed() {
 		return nil, ErrClosedClient
 	}
@@ -217,7 +214,6 @@ func (client *client) Partitions(topic string) ([]int32, error) {
 }
 
 func (client *client) WritablePartitions(topic string) ([]int32, error) {
-	// Check to see whether the client is closed
 	if client.Closed() {
 		return nil, ErrClosedClient
 	}
@@ -271,6 +267,10 @@ func (client *client) Replicas(topic string, partitionID int32) ([]int32, error)
 }
 
 func (client *client) Leader(topic string, partitionID int32) (*Broker, error) {
+	if client.Closed() {
+		return nil, ErrClosedClient
+	}
+
 	leader, err := client.cachedLeader(topic, partitionID)
 
 	if leader == nil {
@@ -302,6 +302,10 @@ func (client *client) RefreshMetadata(topics ...string) error {
 }
 
 func (client *client) GetOffset(topic string, partitionID int32, time int64) (int64, error) {
+	if client.Closed() {
+		return -1, ErrClosedClient
+	}
+
 	offset, err := client.getOffset(topic, partitionID, time)
 
 	if err != nil {
@@ -315,6 +319,10 @@ func (client *client) GetOffset(topic string, partitionID int32, time int64) (in
 }
 
 func (client *client) Coordinator(consumerGroup string) (*Broker, error) {
+	if client.Closed() {
+		return nil, ErrClosedClient
+	}
+
 	coordinator := client.cachedCoordinator(consumerGroup)
 
 	if coordinator == nil {
@@ -333,6 +341,10 @@ func (client *client) Coordinator(consumerGroup string) (*Broker, error) {
 }
 
 func (client *client) RefreshCoordinator(consumerGroup string) error {
+	if client.Closed() {
+		return ErrClosedClient
+	}
+
 	response, err := client.getConsumerMetadata(consumerGroup, client.conf.Metadata.Retry.Max)
 	if err != nil {
 		return err