Flush based on buffer size rather than time

this includes:
- Add Accumulator to the Start() function of service inputs
- For message consumer plugins, use the Accumulator to constantly add
  metrics and make Gather a dummy function
- rework unit tests to match this new behavior.
- make "flush_buffer_when_full" a config option that defaults to true

closes #666

agent/agent.go

@@ -58,7 +58,8 @@ func (a *Agent) Connect() error {
 		}
 		err := o.Output.Connect()
 		if err != nil {
-			log.Printf("Failed to connect to output %s, retrying in 15s, error was '%s' \n", o.Name, err)
+			log.Printf("Failed to connect to output %s, retrying in 15s, "+
+				"error was '%s' \n", o.Name, err)
 			time.Sleep(15 * time.Second)
 			err = o.Output.Connect()
 			if err != nil {
@@ -241,7 +242,7 @@ func (a *Agent) Test() error {
 	return nil
 }
 
-// flush writes a list of points to all configured outputs
+// flush writes a list of metrics to all configured outputs
 func (a *Agent) flush() {
 	var wg sync.WaitGroup
 
@@ -260,7 +261,7 @@ func (a *Agent) flush() {
 	wg.Wait()
 }
 
-// flusher monitors the points input channel and flushes on the minimum interval
+// flusher monitors the metrics input channel and flushes on the minimum interval
 func (a *Agent) flusher(shutdown chan struct{}, metricC chan telegraf.Metric) error {
 	// Inelegant, but this sleep is to allow the Gather threads to run, so that
 	// the flusher will flush after metrics are collected.
@@ -271,14 +272,14 @@ func (a *Agent) flusher(shutdown chan struct{}, metricC chan telegraf.Metric) er
 	for {
 		select {
 		case <-shutdown:
-			log.Println("Hang on, flushing any cached points before shutdown")
+			log.Println("Hang on, flushing any cached metrics before shutdown")
 			a.flush()
 			return nil
 		case <-ticker.C:
 			a.flush()
 		case m := <-metricC:
 			for _, o := range a.Config.Outputs {
-				o.AddPoint(m)
+				o.AddMetric(m)
 			}
 		}
 	}
@@ -318,8 +319,8 @@ func (a *Agent) Run(shutdown chan struct{}) error {
 		a.Config.Agent.Interval.Duration, a.Config.Agent.Debug, a.Config.Agent.Quiet,
 		a.Config.Agent.Hostname, a.Config.Agent.FlushInterval.Duration)
 
-	// channel shared between all input threads for accumulating points
+	// channel shared between all input threads for accumulating metrics
-	metricC := make(chan telegraf.Metric, 1000)
+	metricC := make(chan telegraf.Metric, 10000)
 
 	// Round collection to nearest interval by sleeping
 	if a.Config.Agent.RoundInterval {
@@ -342,7 +343,10 @@ func (a *Agent) Run(shutdown chan struct{}) error {
 		// Start service of any ServicePlugins
 		switch p := input.Input.(type) {
 		case telegraf.ServiceInput:
-			if err := p.Start(); err != nil {
+			acc := NewAccumulator(input.Config, metricC)
+			acc.SetDebug(a.Config.Agent.Debug)
+			acc.setDefaultTags(a.Config.Tags)
+			if err := p.Start(acc); err != nil {
 				log.Printf("Service for input %s failed to start, exiting\n%s\n",
 					input.Name, err.Error())
 				return err

etc/telegraf.conf

@@ -16,23 +16,37 @@
 
 # Configuration for telegraf agent
 [agent]
-  # Default data collection interval for all plugins
+  ### Default data collection interval for all inputs
   interval = "10s"
-  # Rounds collection interval to 'interval'
+  ### Rounds collection interval to 'interval'
-  # ie, if interval="10s" then always collect on :00, :10, :20, etc.
+  ### ie, if interval="10s" then always collect on :00, :10, :20, etc.
   round_interval = true
 
-  # Default data flushing interval for all outputs. You should not set this below
+  ### Telegraf will cache metric_buffer_limit metrics for each output, and will
-  # interval. Maximum flush_interval will be flush_interval + flush_jitter
+  ### flush this buffer on a successful write.
+  metric_buffer_limit = 10000
+  ### Flush the buffer whenever full, regardless of flush_interval.
+  flush_buffer_when_full = true
+
+  ### Collection jitter is used to jitter the collection by a random amount.
+  ### Each plugin will sleep for a random time within jitter before collecting.
+  ### This can be used to avoid many plugins querying things like sysfs at the
+  ### same time, which can have a measurable effect on the system.
+  collection_jitter = "0s"
+
+  ### Default flushing interval for all outputs. You shouldn't set this below
+  ### interval. Maximum flush_interval will be flush_interval + flush_jitter
   flush_interval = "10s"
-  # Jitter the flush interval by a random amount. This is primarily to avoid
+  ### Jitter the flush interval by a random amount. This is primarily to avoid
-  # large write spikes for users running a large number of telegraf instances.
+  ### large write spikes for users running a large number of telegraf instances.
-  # ie, a jitter of 5s and interval 10s means flushes will happen every 10-15s
+  ### ie, a jitter of 5s and interval 10s means flushes will happen every 10-15s
   flush_jitter = "0s"
 
-  # Run telegraf in debug mode
+  ### Run telegraf in debug mode
   debug = false
-  # Override default hostname, if empty use os.Hostname()
+  ### Run telegraf in quiet mode
+  quiet = false
+  ### Override default hostname, if empty use os.Hostname()
   hostname = ""
 
 

input.go

@@ -24,7 +24,7 @@ type ServiceInput interface {
 	Gather(Accumulator) error
 
 	// Start starts the ServiceInput's service, whatever that may be
-	Start() error
+	Start(Accumulator) error
 
 	// Stop stops the services and closes any necessary channels and connections
 	Stop()

internal/config/config.go

@@ -68,7 +68,7 @@ type AgentConfig struct {
 	// same time, which can have a measurable effect on the system.
 	CollectionJitter internal.Duration
 
-	// Interval at which to flush data
+	// FlushInterval is the Interval at which to flush data
 	FlushInterval internal.Duration
 
 	// FlushJitter Jitters the flush interval by a random amount.
@@ -82,6 +82,11 @@ type AgentConfig struct {
 	// full, the oldest metrics will be overwritten.
 	MetricBufferLimit int
 
+	// FlushBufferWhenFull tells Telegraf to flush the metric buffer whenever
+	// it fills up, regardless of FlushInterval. Setting this option to true
+	// does _not_ deactivate FlushInterval.
+	FlushBufferWhenFull bool
+
 	// TODO(cam): Remove UTC and Precision parameters, they are no longer
 	// valid for the agent config. Leaving them here for now for backwards-
 	// compatability
@@ -157,6 +162,8 @@ var header = `##################################################################
   ### Telegraf will cache metric_buffer_limit metrics for each output, and will
   ### flush this buffer on a successful write.
   metric_buffer_limit = 10000
+  ### Flush the buffer whenever full, regardless of flush_interval.
+  flush_buffer_when_full = true
 
   ### Collection jitter is used to jitter the collection by a random amount.
   ### Each plugin will sleep for a random time within jitter before collecting.
@@ -421,8 +428,9 @@ func (c *Config) addOutput(name string, table *ast.Table) error {
 
 	ro := internal_models.NewRunningOutput(name, output, outputConfig)
 	if c.Agent.MetricBufferLimit > 0 {
-		ro.PointBufferLimit = c.Agent.MetricBufferLimit
+		ro.MetricBufferLimit = c.Agent.MetricBufferLimit
 	}
+	ro.FlushBufferWhenFull = c.Agent.FlushBufferWhenFull
 	ro.Quiet = c.Agent.Quiet
 	c.Outputs = append(c.Outputs, ro)
 	return nil

internal/models/running_output.go

@@ -2,22 +2,34 @@ package internal_models
 
 import (
 	"log"
+	"sync"
 	"time"
 
 	"github.com/influxdata/telegraf"
 )
 
-const DEFAULT_POINT_BUFFER_LIMIT = 10000
+const (
+	// Default number of metrics kept between flushes.
+	DEFAULT_METRIC_BUFFER_LIMIT = 10000
+
+	// Limit how many full metric buffers are kept due to failed writes.
+	FULL_METRIC_BUFFERS_LIMIT = 100
+)
 
 type RunningOutput struct {
 	Name                string
 	Output              telegraf.Output
 	Config              *OutputConfig
 	Quiet               bool
-	PointBufferLimit int
+	MetricBufferLimit   int
+	FlushBufferWhenFull bool
 
 	metrics    []telegraf.Metric
-	overwriteCounter int
+	tmpmetrics map[int][]telegraf.Metric
+	overwriteI int
+	mapI       int
+
+	sync.Mutex
 }
 
 func NewRunningOutput(
@@ -28,45 +40,92 @@ func NewRunningOutput(
 	ro := &RunningOutput{
 		Name:              name,
 		metrics:           make([]telegraf.Metric, 0),
+		tmpmetrics:        make(map[int][]telegraf.Metric),
 		Output:            output,
 		Config:            conf,
-		PointBufferLimit: DEFAULT_POINT_BUFFER_LIMIT,
+		MetricBufferLimit: DEFAULT_METRIC_BUFFER_LIMIT,
 	}
 	return ro
 }
 
-func (ro *RunningOutput) AddPoint(point telegraf.Metric) {
+// AddMetric adds a metric to the output. This function can also write cached
+// points if FlushBufferWhenFull is true.
+func (ro *RunningOutput) AddMetric(metric telegraf.Metric) {
 	if ro.Config.Filter.IsActive {
-		if !ro.Config.Filter.ShouldMetricPass(point) {
+		if !ro.Config.Filter.ShouldMetricPass(metric) {
 			return
 		}
 	}
+	ro.Lock()
+	defer ro.Unlock()
 
-	if len(ro.metrics) < ro.PointBufferLimit {
+	if len(ro.metrics) < ro.MetricBufferLimit {
-		ro.metrics = append(ro.metrics, point)
+		ro.metrics = append(ro.metrics, metric)
+	} else {
+		if ro.FlushBufferWhenFull {
+			tmpmetrics := make([]telegraf.Metric, len(ro.metrics))
+			copy(tmpmetrics, ro.metrics)
+			ro.metrics = make([]telegraf.Metric, 0)
+			err := ro.write(tmpmetrics)
+			if err != nil {
+				log.Printf("ERROR writing full metric buffer to output %s, %s",
+					ro.Name, err)
+				if len(ro.tmpmetrics) == FULL_METRIC_BUFFERS_LIMIT {
+					ro.mapI = 0
+					// overwrite one
+					ro.tmpmetrics[ro.mapI] = tmpmetrics
+					ro.mapI++
+				} else {
+					ro.tmpmetrics[ro.mapI] = tmpmetrics
+					ro.mapI++
+				}
+			}
 		} else {
 			log.Printf("WARNING: overwriting cached metrics, you may want to " +
-			"increase the metric_buffer_limit setting in your [agent] config " +
+				"increase the metric_buffer_limit setting in your [agent] " +
-			"if you do not wish to overwrite metrics.\n")
+				"config if you do not wish to overwrite metrics.\n")
-		if ro.overwriteCounter == len(ro.metrics) {
+			if ro.overwriteI == len(ro.metrics) {
-			ro.overwriteCounter = 0
+				ro.overwriteI = 0
+			}
+			ro.metrics[ro.overwriteI] = metric
+			ro.overwriteI++
 		}
-		ro.metrics[ro.overwriteCounter] = point
-		ro.overwriteCounter++
 	}
 }
 
+// Write writes all cached points to this output.
 func (ro *RunningOutput) Write() error {
+	ro.Lock()
+	defer ro.Unlock()
+	err := ro.write(ro.metrics)
+	if err != nil {
+		return err
+	} else {
+		ro.metrics = make([]telegraf.Metric, 0)
+		ro.overwriteI = 0
+	}
+
+	// Write any cached metric buffers that failed previously
+	for i, tmpmetrics := range ro.tmpmetrics {
+		if err := ro.write(tmpmetrics); err != nil {
+			return err
+		} else {
+			delete(ro.tmpmetrics, i)
+		}
+	}
+
+	return nil
+}
+
+func (ro *RunningOutput) write(metrics []telegraf.Metric) error {
 	start := time.Now()
-	err := ro.Output.Write(ro.metrics)
+	err := ro.Output.Write(metrics)
 	elapsed := time.Since(start)
 	if err == nil {
 		if !ro.Quiet {
 			log.Printf("Wrote %d metrics to output %s in %s\n",
-				len(ro.metrics), ro.Name, elapsed)
+				len(metrics), ro.Name, elapsed)
 		}
-		ro.metrics = make([]telegraf.Metric, 0)
-		ro.overwriteCounter = 0
 	}
 	return err
 }

plugins/inputs/github_webhooks/github_webhooks.go

@@ -61,7 +61,7 @@ func (gh *GithubWebhooks) Listen() {
 	}
 }
 
-func (gh *GithubWebhooks) Start() error {
+func (gh *GithubWebhooks) Start(_ telegraf.Accumulator) error {
 	go gh.Listen()
 	log.Printf("Started the github_webhooks service on %s\n", gh.ServiceAddress)
 	return nil

plugins/inputs/kafka_consumer/kafka_consumer.go

@@ -1,7 +1,6 @@
 package kafka_consumer
 
 import (
-	"fmt"
 	"log"
 	"strings"
 	"sync"
@@ -19,11 +18,13 @@ type Kafka struct {
 	Topics         []string
 	ZookeeperPeers []string
 	Consumer       *consumergroup.ConsumerGroup
+
+	// Legacy metric buffer support
 	MetricBuffer int
 	// TODO remove PointBuffer, legacy support
 	PointBuffer int
-	Offset      string
 
+	Offset string
 	parser parsers.Parser
 
 	sync.Mutex
@@ -32,10 +33,11 @@ type Kafka struct {
 	in <-chan *sarama.ConsumerMessage
 	// channel for all kafka consumer errors
 	errs <-chan *sarama.ConsumerError
-	// channel for all incoming parsed kafka metrics
-	metricC chan telegraf.Metric
 	done chan struct{}
 
+	// keep the accumulator internally:
+	acc telegraf.Accumulator
+
 	// doNotCommitMsgs tells the parser not to call CommitUpTo on the consumer
 	// this is mostly for test purposes, but there may be a use-case for it later.
 	doNotCommitMsgs bool
@@ -48,8 +50,6 @@ var sampleConfig = `
   zookeeper_peers = ["localhost:2181"]
   ### the name of the consumer group
   consumer_group = "telegraf_metrics_consumers"
-  ### Maximum number of metrics to buffer between collection intervals
-  metric_buffer = 100000
   ### Offset (must be either "oldest" or "newest")
   offset = "oldest"
 
@@ -72,11 +72,13 @@ func (k *Kafka) SetParser(parser parsers.Parser) {
 	k.parser = parser
 }
 
-func (k *Kafka) Start() error {
+func (k *Kafka) Start(acc telegraf.Accumulator) error {
 	k.Lock()
 	defer k.Unlock()
 	var consumerErr error
 
+	k.acc = acc
+
 	config := consumergroup.NewConfig()
 	switch strings.ToLower(k.Offset) {
 	case "oldest", "":
@@ -106,13 +108,6 @@ func (k *Kafka) Start() error {
 	}
 
 	k.done = make(chan struct{})
-	if k.PointBuffer == 0 && k.MetricBuffer == 0 {
-		k.MetricBuffer = 100000
-	} else if k.PointBuffer > 0 {
-		// Legacy support of PointBuffer field TODO remove
-		k.MetricBuffer = k.PointBuffer
-	}
-	k.metricC = make(chan telegraf.Metric, k.MetricBuffer)
 
 	// Start the kafka message reader
 	go k.receiver()
@@ -138,14 +133,7 @@ func (k *Kafka) receiver() {
 			}
 
 			for _, metric := range metrics {
-				fmt.Println(string(metric.Name()))
+				k.acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())
-				select {
-				case k.metricC <- metric:
-					continue
-				default:
-					log.Printf("Kafka Consumer buffer is full, dropping a metric." +
-						" You may want to increase the metric_buffer setting")
-				}
 			}
 
 			if !k.doNotCommitMsgs {
@@ -169,13 +157,6 @@ func (k *Kafka) Stop() {
 }
 
 func (k *Kafka) Gather(acc telegraf.Accumulator) error {
-	k.Lock()
-	defer k.Unlock()
-	nmetrics := len(k.metricC)
-	for i := 0; i < nmetrics; i++ {
-		metric := <-k.metricC
-		acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())
-	}
 	return nil
 }
 

plugins/inputs/kafka_consumer/kafka_consumer_integration_test.go

@@ -44,18 +44,19 @@ func TestReadsMetricsFromKafka(t *testing.T) {
 	}
 	p, _ := parsers.NewInfluxParser()
 	k.SetParser(p)
-	if err := k.Start(); err != nil {
+
+	// Verify that we can now gather the sent message
+	var acc testutil.Accumulator
+
+	// Sanity check
+	assert.Equal(t, 0, len(acc.Metrics), "There should not be any points")
+	if err := k.Start(&acc); err != nil {
 		t.Fatal(err.Error())
 	} else {
 		defer k.Stop()
 	}
 
-	waitForPoint(k, t)
+	waitForPoint(&acc, t)
-
-	// Verify that we can now gather the sent message
-	var acc testutil.Accumulator
-	// Sanity check
-	assert.Equal(t, 0, len(acc.Metrics), "There should not be any points")
 
 	// Gather points
 	err = k.Gather(&acc)
@@ -77,7 +78,7 @@ func TestReadsMetricsFromKafka(t *testing.T) {
 
 // Waits for the metric that was sent to the kafka broker to arrive at the kafka
 // consumer
-func waitForPoint(k *Kafka, t *testing.T) {
+func waitForPoint(acc *testutil.Accumulator, t *testing.T) {
 	// Give the kafka container up to 2 seconds to get the point to the consumer
 	ticker := time.NewTicker(5 * time.Millisecond)
 	counter := 0
@@ -87,7 +88,7 @@ func waitForPoint(k *Kafka, t *testing.T) {
 			counter++
 			if counter > 1000 {
 				t.Fatal("Waited for 5s, point never arrived to consumer")
-			} else if len(k.metricC) == 1 {
+			} else if acc.NFields() == 1 {
 				return
 			}
 		}

plugins/inputs/kafka_consumer/kafka_consumer_test.go

@@ -4,7 +4,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/plugins/parsers"
 	"github.com/influxdata/telegraf/testutil"
 
@@ -17,29 +16,28 @@ const (
 	testMsgGraphite = "cpu.load.short.graphite 23422 1454780029"
 	testMsgJSON     = "{\"a\": 5, \"b\": {\"c\": 6}}\n"
 	invalidMsg      = "cpu_load_short,host=server01 1422568543702900257"
-	pointBuffer     = 5
 )
 
-func NewTestKafka() (*Kafka, chan *sarama.ConsumerMessage) {
+func newTestKafka() (*Kafka, chan *sarama.ConsumerMessage) {
-	in := make(chan *sarama.ConsumerMessage, pointBuffer)
+	in := make(chan *sarama.ConsumerMessage, 1000)
 	k := Kafka{
 		ConsumerGroup:   "test",
 		Topics:          []string{"telegraf"},
 		ZookeeperPeers:  []string{"localhost:2181"},
-		PointBuffer:     pointBuffer,
 		Offset:          "oldest",
 		in:              in,
 		doNotCommitMsgs: true,
-		errs:            make(chan *sarama.ConsumerError, pointBuffer),
+		errs:            make(chan *sarama.ConsumerError, 1000),
 		done:            make(chan struct{}),
-		metricC:         make(chan telegraf.Metric, pointBuffer),
 	}
 	return &k, in
 }
 
 // Test that the parser parses kafka messages into points
 func TestRunParser(t *testing.T) {
-	k, in := NewTestKafka()
+	k, in := newTestKafka()
+	acc := testutil.Accumulator{}
+	k.acc = &acc
 	defer close(k.done)
 
 	k.parser, _ = parsers.NewInfluxParser()
@@ -47,12 +45,14 @@ func TestRunParser(t *testing.T) {
 	in <- saramaMsg(testMsg)
 	time.Sleep(time.Millisecond)
 
-	assert.Equal(t, len(k.metricC), 1)
+	assert.Equal(t, acc.NFields(), 1)
 }
 
 // Test that the parser ignores invalid messages
 func TestRunParserInvalidMsg(t *testing.T) {
-	k, in := NewTestKafka()
+	k, in := newTestKafka()
+	acc := testutil.Accumulator{}
+	k.acc = &acc
 	defer close(k.done)
 
 	k.parser, _ = parsers.NewInfluxParser()
@@ -60,27 +60,14 @@ func TestRunParserInvalidMsg(t *testing.T) {
 	in <- saramaMsg(invalidMsg)
 	time.Sleep(time.Millisecond)
 
-	assert.Equal(t, len(k.metricC), 0)
+	assert.Equal(t, acc.NFields(), 0)
-}
-
-// Test that points are dropped when we hit the buffer limit
-func TestRunParserRespectsBuffer(t *testing.T) {
-	k, in := NewTestKafka()
-	defer close(k.done)
-
-	k.parser, _ = parsers.NewInfluxParser()
-	go k.receiver()
-	for i := 0; i < pointBuffer+1; i++ {
-		in <- saramaMsg(testMsg)
-	}
-	time.Sleep(time.Millisecond)
-
-	assert.Equal(t, len(k.metricC), 5)
 }
 
 // Test that the parser parses kafka messages into points
 func TestRunParserAndGather(t *testing.T) {
-	k, in := NewTestKafka()
+	k, in := newTestKafka()
+	acc := testutil.Accumulator{}
+	k.acc = &acc
 	defer close(k.done)
 
 	k.parser, _ = parsers.NewInfluxParser()
@@ -88,17 +75,18 @@ func TestRunParserAndGather(t *testing.T) {
 	in <- saramaMsg(testMsg)
 	time.Sleep(time.Millisecond)
 
-	acc := testutil.Accumulator{}
 	k.Gather(&acc)
 
-	assert.Equal(t, len(acc.Metrics), 1)
+	assert.Equal(t, acc.NFields(), 1)
 	acc.AssertContainsFields(t, "cpu_load_short",
 		map[string]interface{}{"value": float64(23422)})
 }
 
 // Test that the parser parses kafka messages into points
 func TestRunParserAndGatherGraphite(t *testing.T) {
-	k, in := NewTestKafka()
+	k, in := newTestKafka()
+	acc := testutil.Accumulator{}
+	k.acc = &acc
 	defer close(k.done)
 
 	k.parser, _ = parsers.NewGraphiteParser("_", []string{}, nil)
@@ -106,17 +94,18 @@ func TestRunParserAndGatherGraphite(t *testing.T) {
 	in <- saramaMsg(testMsgGraphite)
 	time.Sleep(time.Millisecond)
 
-	acc := testutil.Accumulator{}
 	k.Gather(&acc)
 
-	assert.Equal(t, len(acc.Metrics), 1)
+	assert.Equal(t, acc.NFields(), 1)
 	acc.AssertContainsFields(t, "cpu_load_short_graphite",
 		map[string]interface{}{"value": float64(23422)})
 }
 
 // Test that the parser parses kafka messages into points
 func TestRunParserAndGatherJSON(t *testing.T) {
-	k, in := NewTestKafka()
+	k, in := newTestKafka()
+	acc := testutil.Accumulator{}
+	k.acc = &acc
 	defer close(k.done)
 
 	k.parser, _ = parsers.NewJSONParser("kafka_json_test", []string{}, nil)
@@ -124,10 +113,9 @@ func TestRunParserAndGatherJSON(t *testing.T) {
 	in <- saramaMsg(testMsgJSON)
 	time.Sleep(time.Millisecond)
 
-	acc := testutil.Accumulator{}
 	k.Gather(&acc)
 
-	assert.Equal(t, len(acc.Metrics), 1)
+	assert.Equal(t, acc.NFields(), 2)
 	acc.AssertContainsFields(t, "kafka_json_test",
 		map[string]interface{}{
 			"a":   float64(5),

plugins/inputs/mqtt_consumer/mqtt_consumer.go

@@ -19,11 +19,13 @@ type MQTTConsumer struct {
 	Topics   []string
 	Username string
 	Password string
-	MetricBuffer int
 	QoS      int `toml:"qos"`
 
 	parser parsers.Parser
 
+	// Legacy metric buffer support
+	MetricBuffer int
+
 	// Path to CA file
 	SSLCA string `toml:"ssl_ca"`
 	// Path to host cert file
@@ -35,13 +37,12 @@ type MQTTConsumer struct {
 
 	sync.Mutex
 	client *mqtt.Client
-	// channel for all incoming parsed mqtt metrics
-	metricC chan telegraf.Metric
-	// channel for the topics of all incoming metrics (for tagging metrics)
-	topicC chan string
 	// channel of all incoming raw mqtt messages
 	in   chan mqtt.Message
 	done chan struct{}
+
+	// keep the accumulator internally:
+	acc telegraf.Accumulator
 }
 
 var sampleConfig = `
@@ -56,9 +57,6 @@ var sampleConfig = `
     "sensors/#",
   ]
 
-  ### Maximum number of metrics to buffer between collection intervals
-  metric_buffer = 100000
-
   ### username and password to connect MQTT server.
   # username = "telegraf"
   # password = "metricsmetricsmetricsmetrics"
@@ -89,9 +87,11 @@ func (m *MQTTConsumer) SetParser(parser parsers.Parser) {
 	m.parser = parser
 }
 
-func (m *MQTTConsumer) Start() error {
+func (m *MQTTConsumer) Start(acc telegraf.Accumulator) error {
 	m.Lock()
 	defer m.Unlock()
+
+	m.acc = acc
 	if m.QoS > 2 || m.QoS < 0 {
 		return fmt.Errorf("MQTT Consumer, invalid QoS value: %d", m.QoS)
 	}
@@ -106,13 +106,8 @@ func (m *MQTTConsumer) Start() error {
 		return token.Error()
 	}
 
-	m.in = make(chan mqtt.Message, m.MetricBuffer)
+	m.in = make(chan mqtt.Message, 1000)
 	m.done = make(chan struct{})
-	if m.MetricBuffer == 0 {
-		m.MetricBuffer = 100000
-	}
-	m.metricC = make(chan telegraf.Metric, m.MetricBuffer)
-	m.topicC = make(chan string, m.MetricBuffer)
 
 	topics := make(map[string]byte)
 	for _, topic := range m.Topics {
@@ -145,13 +140,9 @@ func (m *MQTTConsumer) receiver() {
 			}
 
 			for _, metric := range metrics {
-				select {
+				tags := metric.Tags()
-				case m.metricC <- metric:
+				tags["topic"] = topic
-					m.topicC <- topic
+				m.acc.AddFields(metric.Name(), metric.Fields(), tags, metric.Time())
-				default:
-					log.Printf("MQTT Consumer buffer is full, dropping a metric." +
-						" You may want to increase the metric_buffer setting")
-				}
 			}
 		}
 	}
@@ -169,16 +160,6 @@ func (m *MQTTConsumer) Stop() {
 }
 
 func (m *MQTTConsumer) Gather(acc telegraf.Accumulator) error {
-	m.Lock()
-	defer m.Unlock()
-	nmetrics := len(m.metricC)
-	for i := 0; i < nmetrics; i++ {
-		metric := <-m.metricC
-		topic := <-m.topicC
-		tags := metric.Tags()
-		tags["topic"] = topic
-		acc.AddFields(metric.Name(), metric.Fields(), tags, metric.Time())
-	}
 	return nil
 }
 

plugins/inputs/mqtt_consumer/mqtt_consumer_test.go

@@ -4,7 +4,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/plugins/parsers"
 	"github.com/influxdata/telegraf/testutil"
 
@@ -16,19 +15,15 @@ const (
 	testMsgGraphite = "cpu.load.short.graphite 23422 1454780029"
 	testMsgJSON     = "{\"a\": 5, \"b\": {\"c\": 6}}\n"
 	invalidMsg      = "cpu_load_short,host=server01 1422568543702900257"
-	metricBuffer    = 5
 )
 
 func newTestMQTTConsumer() (*MQTTConsumer, chan mqtt.Message) {
-	in := make(chan mqtt.Message, metricBuffer)
+	in := make(chan mqtt.Message, 100)
 	n := &MQTTConsumer{
 		Topics:  []string{"telegraf"},
 		Servers: []string{"localhost:1883"},
-		MetricBuffer: metricBuffer,
 		in:      in,
 		done:    make(chan struct{}),
-		metricC:      make(chan telegraf.Metric, metricBuffer),
-		topicC:       make(chan string, metricBuffer),
 	}
 	return n, in
 }
@@ -36,14 +31,16 @@ func newTestMQTTConsumer() (*MQTTConsumer, chan mqtt.Message) {
 // Test that the parser parses NATS messages into metrics
 func TestRunParser(t *testing.T) {
 	n, in := newTestMQTTConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- mqttMsg(testMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	if a := len(n.metricC); a != 1 {
+	if a := acc.NFields(); a != 1 {
 		t.Errorf("got %v, expected %v", a, 1)
 	}
 }
@@ -51,51 +48,34 @@ func TestRunParser(t *testing.T) {
 // Test that the parser ignores invalid messages
 func TestRunParserInvalidMsg(t *testing.T) {
 	n, in := newTestMQTTConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- mqttMsg(invalidMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	if a := len(n.metricC); a != 0 {
+	if a := acc.NFields(); a != 0 {
 		t.Errorf("got %v, expected %v", a, 0)
 	}
 }
 
-// Test that metrics are dropped when we hit the buffer limit
-func TestRunParserRespectsBuffer(t *testing.T) {
-	n, in := newTestMQTTConsumer()
-	defer close(n.done)
-
-	n.parser, _ = parsers.NewInfluxParser()
-	go n.receiver()
-	for i := 0; i < metricBuffer+1; i++ {
-		in <- mqttMsg(testMsg)
-	}
-	time.Sleep(time.Millisecond)
-
-	if a := len(n.metricC); a != metricBuffer {
-		t.Errorf("got %v, expected %v", a, metricBuffer)
-	}
-}
-
 // Test that the parser parses line format messages into metrics
 func TestRunParserAndGather(t *testing.T) {
 	n, in := newTestMQTTConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- mqttMsg(testMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "cpu_load_short",
 		map[string]interface{}{"value": float64(23422)})
 }
@@ -103,19 +83,17 @@ func TestRunParserAndGather(t *testing.T) {
 // Test that the parser parses graphite format messages into metrics
 func TestRunParserAndGatherGraphite(t *testing.T) {
 	n, in := newTestMQTTConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewGraphiteParser("_", []string{}, nil)
 	go n.receiver()
 	in <- mqttMsg(testMsgGraphite)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "cpu_load_short_graphite",
 		map[string]interface{}{"value": float64(23422)})
 }
@@ -123,19 +101,17 @@ func TestRunParserAndGatherGraphite(t *testing.T) {
 // Test that the parser parses json format messages into metrics
 func TestRunParserAndGatherJSON(t *testing.T) {
 	n, in := newTestMQTTConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewJSONParser("nats_json_test", []string{}, nil)
 	go n.receiver()
 	in <- mqttMsg(testMsgJSON)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "nats_json_test",
 		map[string]interface{}{
 			"a":   float64(5),

plugins/inputs/nats_consumer/nats_consumer.go

@@ -28,7 +28,9 @@ type natsConsumer struct {
 	Servers    []string
 	Secure     bool
 
+	// Legacy metric buffer support
 	MetricBuffer int
+
 	parser parsers.Parser
 
 	sync.Mutex
@@ -39,9 +41,8 @@ type natsConsumer struct {
 	in chan *nats.Msg
 	// channel for all NATS read errors
 	errs chan error
-	// channel for all incoming parsed metrics
-	metricC chan telegraf.Metric
 	done chan struct{}
+	acc  telegraf.Accumulator
 }
 
 var sampleConfig = `
@@ -53,8 +54,6 @@ var sampleConfig = `
   subjects = ["telegraf"]
   ### name a queue group
   queue_group = "telegraf_consumers"
-  ### Maximum number of metrics to buffer between collection intervals
-  metric_buffer = 100000
 
   ### Data format to consume. This can be "json", "influx" or "graphite"
   ### Each data format has it's own unique set of configuration options, read
@@ -84,10 +83,12 @@ func (n *natsConsumer) natsErrHandler(c *nats.Conn, s *nats.Subscription, e erro
 }
 
 // Start the nats consumer. Caller must call *natsConsumer.Stop() to clean up.
-func (n *natsConsumer) Start() error {
+func (n *natsConsumer) Start(acc telegraf.Accumulator) error {
 	n.Lock()
 	defer n.Unlock()
 
+	n.acc = acc
+
 	var connectErr error
 
 	opts := nats.DefaultOptions
@@ -115,11 +116,6 @@ func (n *natsConsumer) Start() error {
 	}
 
 	n.done = make(chan struct{})
-	if n.MetricBuffer == 0 {
-		n.MetricBuffer = 100000
-	}
-
-	n.metricC = make(chan telegraf.Metric, n.MetricBuffer)
 
 	// Start the message reader
 	go n.receiver()
@@ -146,13 +142,7 @@ func (n *natsConsumer) receiver() {
 			}
 
 			for _, metric := range metrics {
-				select {
+				n.acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())
-				case n.metricC <- metric:
-					continue
-				default:
-					log.Printf("NATS Consumer buffer is full, dropping a metric." +
-						" You may want to increase the metric_buffer setting")
-				}
 			}
 
 		}
@@ -163,7 +153,6 @@ func (n *natsConsumer) clean() {
 	n.Lock()
 	defer n.Unlock()
 	close(n.in)
-	close(n.metricC)
 	close(n.errs)
 
 	for _, sub := range n.Subs {
@@ -185,13 +174,6 @@ func (n *natsConsumer) Stop() {
 }
 
 func (n *natsConsumer) Gather(acc telegraf.Accumulator) error {
-	n.Lock()
-	defer n.Unlock()
-	nmetrics := len(n.metricC)
-	for i := 0; i < nmetrics; i++ {
-		metric := <-n.metricC
-		acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), metric.Time())
-	}
 	return nil
 }
 

plugins/inputs/nats_consumer/nats_consumer_test.go

@@ -4,7 +4,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/plugins/parsers"
 	"github.com/influxdata/telegraf/testutil"
 	"github.com/nats-io/nats"
@@ -25,11 +24,9 @@ func newTestNatsConsumer() (*natsConsumer, chan *nats.Msg) {
 		Subjects:   []string{"telegraf"},
 		Servers:    []string{"nats://localhost:4222"},
 		Secure:     false,
-		MetricBuffer: metricBuffer,
 		in:         in,
 		errs:       make(chan error, metricBuffer),
 		done:       make(chan struct{}),
-		metricC:      make(chan telegraf.Metric, metricBuffer),
 	}
 	return n, in
 }
@@ -37,66 +34,51 @@ func newTestNatsConsumer() (*natsConsumer, chan *nats.Msg) {
 // Test that the parser parses NATS messages into metrics
 func TestRunParser(t *testing.T) {
 	n, in := newTestNatsConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- natsMsg(testMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	if a := len(n.metricC); a != 1 {
+	if acc.NFields() != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
+		t.Errorf("got %v, expected %v", acc.NFields(), 1)
 	}
 }
 
 // Test that the parser ignores invalid messages
 func TestRunParserInvalidMsg(t *testing.T) {
 	n, in := newTestNatsConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- natsMsg(invalidMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	if a := len(n.metricC); a != 0 {
+	if acc.NFields() != 0 {
-		t.Errorf("got %v, expected %v", a, 0)
+		t.Errorf("got %v, expected %v", acc.NFields(), 0)
-	}
-}
-
-// Test that metrics are dropped when we hit the buffer limit
-func TestRunParserRespectsBuffer(t *testing.T) {
-	n, in := newTestNatsConsumer()
-	defer close(n.done)
-
-	n.parser, _ = parsers.NewInfluxParser()
-	go n.receiver()
-	for i := 0; i < metricBuffer+1; i++ {
-		in <- natsMsg(testMsg)
-	}
-	time.Sleep(time.Millisecond)
-
-	if a := len(n.metricC); a != metricBuffer {
-		t.Errorf("got %v, expected %v", a, metricBuffer)
 	}
 }
 
 // Test that the parser parses line format messages into metrics
 func TestRunParserAndGather(t *testing.T) {
 	n, in := newTestNatsConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewInfluxParser()
 	go n.receiver()
 	in <- natsMsg(testMsg)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "cpu_load_short",
 		map[string]interface{}{"value": float64(23422)})
 }
@@ -104,19 +86,17 @@ func TestRunParserAndGather(t *testing.T) {
 // Test that the parser parses graphite format messages into metrics
 func TestRunParserAndGatherGraphite(t *testing.T) {
 	n, in := newTestNatsConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewGraphiteParser("_", []string{}, nil)
 	go n.receiver()
 	in <- natsMsg(testMsgGraphite)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "cpu_load_short_graphite",
 		map[string]interface{}{"value": float64(23422)})
 }
@@ -124,19 +104,17 @@ func TestRunParserAndGatherGraphite(t *testing.T) {
 // Test that the parser parses json format messages into metrics
 func TestRunParserAndGatherJSON(t *testing.T) {
 	n, in := newTestNatsConsumer()
+	acc := testutil.Accumulator{}
+	n.acc = &acc
 	defer close(n.done)
 
 	n.parser, _ = parsers.NewJSONParser("nats_json_test", []string{}, nil)
 	go n.receiver()
 	in <- natsMsg(testMsgJSON)
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond * 25)
 
-	acc := testutil.Accumulator{}
 	n.Gather(&acc)
 
-	if a := len(acc.Metrics); a != 1 {
-		t.Errorf("got %v, expected %v", a, 1)
-	}
 	acc.AssertContainsFields(t, "nats_json_test",
 		map[string]interface{}{
 			"a":   float64(5),

plugins/inputs/statsd/statsd.go

@@ -213,7 +213,7 @@ func (s *Statsd) Gather(acc telegraf.Accumulator) error {
 	return nil
 }
 
-func (s *Statsd) Start() error {
+func (s *Statsd) Start(_ telegraf.Accumulator) error {
 	// Make data structures
 	s.done = make(chan struct{})
 	s.in = make(chan []byte, s.AllowedPendingMessages)

testutil/accumulator.go

@@ -108,6 +108,8 @@ func (a *Accumulator) Get(measurement string) (*Metric, bool) {
 // NFields returns the total number of fields in the accumulator, across all
 // measurements
 func (a *Accumulator) NFields() int {
+	a.Lock()
+	defer a.Unlock()
 	counter := 0
 	for _, pt := range a.Metrics {
 		for _, _ = range pt.Fields {
@@ -123,6 +125,8 @@ func (a *Accumulator) AssertContainsTaggedFields(
 	fields map[string]interface{},
 	tags map[string]string,
 ) {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if !reflect.DeepEqual(tags, p.Tags) {
 			continue
@@ -148,6 +152,8 @@ func (a *Accumulator) AssertContainsFields(
 	measurement string,
 	fields map[string]interface{},
 ) {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if p.Measurement == measurement {
 			if !reflect.DeepEqual(fields, p.Fields) {
@@ -166,6 +172,8 @@ func (a *Accumulator) AssertContainsFields(
 
 // HasIntValue returns true if the measurement has an Int value
 func (a *Accumulator) HasIntField(measurement string, field string) bool {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if p.Measurement == measurement {
 			for fieldname, value := range p.Fields {
@@ -182,6 +190,8 @@ func (a *Accumulator) HasIntField(measurement string, field string) bool {
 
 // HasUIntValue returns true if the measurement has a UInt value
 func (a *Accumulator) HasUIntField(measurement string, field string) bool {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if p.Measurement == measurement {
 			for fieldname, value := range p.Fields {
@@ -198,6 +208,8 @@ func (a *Accumulator) HasUIntField(measurement string, field string) bool {
 
 // HasFloatValue returns true if the given measurement has a float value
 func (a *Accumulator) HasFloatField(measurement string, field string) bool {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if p.Measurement == measurement {
 			for fieldname, value := range p.Fields {
@@ -215,6 +227,8 @@ func (a *Accumulator) HasFloatField(measurement string, field string) bool {
 // HasMeasurement returns true if the accumulator has a measurement with the
 // given name
 func (a *Accumulator) HasMeasurement(measurement string) bool {
+	a.Lock()
+	defer a.Unlock()
 	for _, p := range a.Metrics {
 		if p.Measurement == measurement {
 			return true