Opentracing support

vendor/github.com/Shopify/sarama/partitioner.go

@@ -0,0 +1,135 @@
+package sarama
+
+import (
+	"hash"
+	"hash/fnv"
+	"math/rand"
+	"time"
+)
+
+// Partitioner is anything that, given a Kafka message and a number of partitions indexed [0...numPartitions-1],
+// decides to which partition to send the message. RandomPartitioner, RoundRobinPartitioner and HashPartitioner are provided
+// as simple default implementations.
+type Partitioner interface {
+	// Partition takes a message and partition count and chooses a partition
+	Partition(message *ProducerMessage, numPartitions int32) (int32, error)
+
+	// RequiresConsistency indicates to the user of the partitioner whether the
+	// mapping of key->partition is consistent or not. Specifically, if a
+	// partitioner requires consistency then it must be allowed to choose from all
+	// partitions (even ones known to be unavailable), and its choice must be
+	// respected by the caller. The obvious example is the HashPartitioner.
+	RequiresConsistency() bool
+}
+
+// PartitionerConstructor is the type for a function capable of constructing new Partitioners.
+type PartitionerConstructor func(topic string) Partitioner
+
+type manualPartitioner struct{}
+
+// NewManualPartitioner returns a Partitioner which uses the partition manually set in the provided
+// ProducerMessage's Partition field as the partition to produce to.
+func NewManualPartitioner(topic string) Partitioner {
+	return new(manualPartitioner)
+}
+
+func (p *manualPartitioner) Partition(message *ProducerMessage, numPartitions int32) (int32, error) {
+	return message.Partition, nil
+}
+
+func (p *manualPartitioner) RequiresConsistency() bool {
+	return true
+}
+
+type randomPartitioner struct {
+	generator *rand.Rand
+}
+
+// NewRandomPartitioner returns a Partitioner which chooses a random partition each time.
+func NewRandomPartitioner(topic string) Partitioner {
+	p := new(randomPartitioner)
+	p.generator = rand.New(rand.NewSource(time.Now().UTC().UnixNano()))
+	return p
+}
+
+func (p *randomPartitioner) Partition(message *ProducerMessage, numPartitions int32) (int32, error) {
+	return int32(p.generator.Intn(int(numPartitions))), nil
+}
+
+func (p *randomPartitioner) RequiresConsistency() bool {
+	return false
+}
+
+type roundRobinPartitioner struct {
+	partition int32
+}
+
+// NewRoundRobinPartitioner returns a Partitioner which walks through the available partitions one at a time.
+func NewRoundRobinPartitioner(topic string) Partitioner {
+	return &roundRobinPartitioner{}
+}
+
+func (p *roundRobinPartitioner) Partition(message *ProducerMessage, numPartitions int32) (int32, error) {
+	if p.partition >= numPartitions {
+		p.partition = 0
+	}
+	ret := p.partition
+	p.partition++
+	return ret, nil
+}
+
+func (p *roundRobinPartitioner) RequiresConsistency() bool {
+	return false
+}
+
+type hashPartitioner struct {
+	random Partitioner
+	hasher hash.Hash32
+}
+
+// NewCustomHashPartitioner is a wrapper around NewHashPartitioner, allowing the use of custom hasher.
+// The argument is a function providing the instance, implementing the hash.Hash32 interface. This is to ensure that
+// each partition dispatcher gets its own hasher, to avoid concurrency issues by sharing an instance.
+func NewCustomHashPartitioner(hasher func() hash.Hash32) PartitionerConstructor {
+	return func(topic string) Partitioner {
+		p := new(hashPartitioner)
+		p.random = NewRandomPartitioner(topic)
+		p.hasher = hasher()
+		return p
+	}
+}
+
+// NewHashPartitioner returns a Partitioner which behaves as follows. If the message's key is nil then a
+// random partition is chosen. Otherwise the FNV-1a hash of the encoded bytes of the message key is used,
+// modulus the number of partitions. This ensures that messages with the same key always end up on the
+// same partition.
+func NewHashPartitioner(topic string) Partitioner {
+	p := new(hashPartitioner)
+	p.random = NewRandomPartitioner(topic)
+	p.hasher = fnv.New32a()
+	return p
+}
+
+func (p *hashPartitioner) Partition(message *ProducerMessage, numPartitions int32) (int32, error) {
+	if message.Key == nil {
+		return p.random.Partition(message, numPartitions)
+	}
+	bytes, err := message.Key.Encode()
+	if err != nil {
+		return -1, err
+	}
+	p.hasher.Reset()
+	_, err = p.hasher.Write(bytes)
+	if err != nil {
+		return -1, err
+	}
+	partition := int32(p.hasher.Sum32()) % numPartitions
+	if partition < 0 {
+		partition = -partition
+	}
+	return partition, nil
+}
+
+func (p *hashPartitioner) RequiresConsistency() bool {
+	return true
+}