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
-	metricC := make(chan telegraf.Metric, 1000)
+	// channel shared between all input threads for accumulating metrics
+	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'
-  # ie, if interval="10s" then always collect on :00, :10, :20, etc.
+  ### Rounds collection interval to 'interval'
+  ### 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
-  # interval. Maximum flush_interval will be flush_interval + flush_jitter
+  ### 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.
+  ### 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
-  # 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
+  ### 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.
+  ### 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
+	Name                string
+	Output              telegraf.Output
+	Config              *OutputConfig
+	Quiet               bool
+	MetricBufferLimit   int
+	FlushBufferWhenFull bool
 
-	metrics          []telegraf.Metric
-	overwriteCounter int
+	metrics    []telegraf.Metric
+	tmpmetrics map[int][]telegraf.Metric
+	overwriteI int
+	mapI       int
+
+	sync.Mutex
 }
 
 func NewRunningOutput(
@@ -26,47 +38,94 @@ func NewRunningOutput(
 	conf *OutputConfig,
 ) *RunningOutput {
 	ro := &RunningOutput{
-		Name:             name,
-		metrics:          make([]telegraf.Metric, 0),
-		Output:           output,
-		Config:           conf,
-		PointBufferLimit: DEFAULT_POINT_BUFFER_LIMIT,
+		Name:              name,
+		metrics:           make([]telegraf.Metric, 0),
+		tmpmetrics:        make(map[int][]telegraf.Metric),
+		Output:            output,
+		Config:            conf,
+		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 {
-		ro.metrics = append(ro.metrics, point)
+	if len(ro.metrics) < ro.MetricBufferLimit {
+		ro.metrics = append(ro.metrics, metric)
 	} else {
-		log.Printf("WARNING: overwriting cached metrics, you may want to " +
-			"increase the metric_buffer_limit setting in your [agent] config " +
-			"if you do not wish to overwrite metrics.\n")
-		if ro.overwriteCounter == len(ro.metrics) {
-			ro.overwriteCounter = 0
+		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 if you do not wish to overwrite metrics.\n")
+			if ro.overwriteI == len(ro.metrics) {
+				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