Add a metric for number of partitions held

ref #1126

Signed-off-by: Prithvi Raj <p.r@uber.com>

cmd/ingester/app/consumer/consumer.go

@@ -46,6 +46,7 @@ type Consumer struct {
 	deadlockDetector deadlockDetector
 
 	partitionIDToState map[int32]*consumerState
+	partitionsHeld     metrics.Counter
 }
 
 type consumerState struct {
@@ -63,6 +64,7 @@ func New(params Params) (*Consumer, error) {
 		processorFactory:   params.ProcessorFactory,
 		deadlockDetector:   deadlockDetector,
 		partitionIDToState: make(map[int32]*consumerState),
+		partitionsHeld:     partitionsHeld(params.MetricsFactory),
 	}, nil
 }
 
@@ -100,6 +102,8 @@ func (c *Consumer) Close() error {
 
 func (c *Consumer) handleMessages(pc sc.PartitionConsumer) {
 	c.logger.Info("Starting message handler", zap.Int32("partition", pc.Partition()))
+	c.partitionsHeld.Inc(1)
+	defer c.partitionsHeld.Inc(-1)
 	c.partitionIDToState[pc.Partition()].wg.Add(1)
 	defer c.partitionIDToState[pc.Partition()].wg.Done()
 	defer c.closePartition(pc)

cmd/ingester/app/consumer/consumer_metrics.go

@@ -20,6 +20,8 @@ import (
 	"github.com/uber/jaeger-lib/metrics"
 )
 
+const consumerNamespace = "sarama-consumer"
+
 type msgMetrics struct {
 	counter     metrics.Counter
 	offsetGauge metrics.Gauge
@@ -36,7 +38,7 @@ type partitionMetrics struct {
 }
 
 func (c *Consumer) namespace(partition int32) metrics.Factory {
-	return c.metricsFactory.Namespace("sarama-consumer", map[string]string{"partition": strconv.Itoa(int(partition))})
+	return c.metricsFactory.Namespace(consumerNamespace, map[string]string{"partition": strconv.Itoa(int(partition))})
 }
 
 func (c *Consumer) newMsgMetrics(partition int32) msgMetrics {
@@ -58,3 +60,7 @@ func (c *Consumer) partitionMetrics(partition int32) partitionMetrics {
 		closeCounter: f.Counter("partition-close", nil),
 		startCounter: f.Counter("partition-start", nil)}
 }
+
+func partitionsHeld(metricsFactory metrics.Factory) metrics.Counter {
+	return metricsFactory.Namespace(consumerNamespace, nil).Counter("partitions-held", nil)
+}

cmd/ingester/app/consumer/consumer_test.go

@@ -47,7 +47,7 @@ const (
 )
 
 func TestConstructor(t *testing.T) {
-	newConsumer, err := New(Params{})
+	newConsumer, err := New(Params{MetricsFactory: metrics.NullFactory})
 	assert.NoError(t, err)
 	assert.NotNil(t, newConsumer)
 }
@@ -83,23 +83,24 @@ func newSaramaClusterConsumer(saramaPartitionConsumer sarama.PartitionConsumer)
 }
 
 func newConsumer(
-	factory metrics.Factory,
+	metricsFactory metrics.Factory,
 	topic string,
 	processor processor.SpanProcessor,
 	consumer consumer.Consumer) *Consumer {
 
 	logger, _ := zap.NewDevelopment()
 	return &Consumer{
-		metricsFactory:     factory,
+		metricsFactory:     metricsFactory,
 		logger:             logger,
 		internalConsumer:   consumer,
 		partitionIDToState: make(map[int32]*consumerState),
-		deadlockDetector:   newDeadlockDetector(factory, logger, time.Second),
+		partitionsHeld:     partitionsHeld(metricsFactory),
+		deadlockDetector:   newDeadlockDetector(metricsFactory, logger, time.Second),
 
 		processorFactory: ProcessorFactory{
 			topic:          topic,
 			consumer:       consumer,
-			metricsFactory: factory,
+			metricsFactory: metricsFactory,
 			logger:         logger,
 			baseProcessor:  processor,
 			parallelism:    1,
@@ -152,12 +153,22 @@ func TestSaramaConsumerWrapper_start_Messages(t *testing.T) {
 	mc.YieldMessage(msg)
 	isProcessed.Wait()
 
+	testutils.AssertCounterMetrics(t, localFactory, testutils.ExpectedMetric{
+		Name:  "sarama-consumer.partitions-held",
+		Value: 1,
+	})
+
 	mp.AssertExpectations(t)
 	// Ensure that the partition consumer was updated in the map
 	assert.Equal(t, saramaPartitionConsumer.HighWaterMarkOffset(),
 		undertest.partitionIDToState[partition].partitionConsumer.HighWaterMarkOffset())
 	undertest.Close()
 
+	testutils.AssertCounterMetrics(t, localFactory, testutils.ExpectedMetric{
+		Name:  "sarama-consumer.partitions-held",
+		Value: 0,
+	})
+
 	partitionTag := map[string]string{"partition": fmt.Sprint(partition)}
 	testutils.AssertCounterMetrics(t, localFactory, testutils.ExpectedMetric{
 		Name:  "sarama-consumer.messages",