Add Isr to Client interface

client.go

@@ -38,6 +38,9 @@ type Client interface {
 	// Replicas returns the set of all replica IDs for the given partition.
 	Replicas(topic string, partitionID int32) ([]int32, error)
 
+	// Isr returns the set of in-sync replica IDs for the given partition.
+	Isr(topic string, partitionID int32) ([]int32, error)
+
 	// RefreshMetadata takes a list of topics and queries the cluster to refresh the
 	// available metadata for those topics. If no topics are provided, it will refresh
 	// metadata for all topics.

client_test.go

@@ -196,6 +196,17 @@ func TestClientMetadata(t *testing.T) {
 		t.Error("Incorrect (or unsorted) replica")
 	}
 
+	isr, err = client.Isr("my_topic", 0)
+	if err != nil {
+		t.Error(err)
+	} else if len(isr) != 2 {
+		t.Error("Client returned incorrect ISRs for partition:", isr)
+	} else if isr[0] != 1 {
+		t.Error("Incorrect (or unsorted) ISR:", isr)
+	} else if isr[1] != 5 {
+		t.Error("Incorrect (or unsorted) ISR:", isr)
+	}
+
 	leader.Close()
 	seedBroker.Close()
 	safeClose(t, client)