Implement ConstantPartitioner

partitioner.go

@@ -84,3 +84,12 @@ func (p *HashPartitioner) Partition(key Encoder, numPartitions int32) int32 {
 	}
 	return hash % numPartitions
 }
+
+// ConstantPartitioner implements the Partitioner interface by just returning a constant value.
+type ConstantPartitioner struct {
+	Constant int32
+}
+
+func (p *ConstantPartitioner) Partition(key Encoder, numPartitions int32) int32 {
+	return p.Constant
+}

partitioner_test.go

@@ -72,3 +72,14 @@ func TestHashPartitioner(t *testing.T) {
 		assertPartitioningConsistent(t, partitioner, ByteEncoder(buf), 50)
 	}
 }
+
+func TestConstantPartitioner(t *testing.T) {
+	partitioner := &ConstantPartitioner{Constant: 0}
+
+	for i := 1; i < 50; i++ {
+		choice := partitioner.Partition(nil, 50)
+		if choice != 0 {
+			t.Error("Returned partition", choice, "instead of 0.")
+		}
+	}
+}