From 1aa969aabcbd4c446fccc12558446bf7346fad04 Mon Sep 17 00:00:00 2001
From: Daniel Nelson <daniel.nelson@influxdb.com>
Date: Wed, 12 Sep 2018 00:23:50 -0700
Subject: [PATCH] Use separate mutexes for write and aggregation in
 running_output

---
 internal/models/running_output.go | 15 +++++++++------
 output.go                         | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/internal/models/running_output.go b/internal/models/running_output.go
index 014202454..bad1f7659 100644
--- a/internal/models/running_output.go
+++ b/internal/models/running_output.go
@@ -36,8 +36,10 @@ type RunningOutput struct {
 	metrics     *buffer.Buffer
 	failMetrics *buffer.Buffer
 
+	// Guards against concurrent calls to Add, Push, Reset
+	aggMutex sync.Mutex
 	// Guards against concurrent calls to the Output as described in #3009
-	sync.Mutex
+	writeMutex sync.Mutex
 }
 
 func NewRunningOutput(
@@ -94,8 +96,6 @@ func NewRunningOutput(
 // AddMetric adds a metric to the output. This function can also write cached
 // points if FlushBufferWhenFull is true.
 func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
-	ro.Lock()
-	defer ro.Unlock()
 
 	if m == nil {
 		return
@@ -118,7 +118,9 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 	}
 
 	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		ro.aggMutex.Lock()
 		output.Add(m)
+		ro.aggMutex.Unlock()
 		return
 	}
 
@@ -135,13 +137,12 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 
 // Write writes all cached points to this output.
 func (ro *RunningOutput) Write() error {
-	ro.Lock()
-	defer ro.Unlock()
-
 	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		ro.aggMutex.Lock()
 		metrics := output.Push()
 		ro.metrics.Add(metrics...)
 		output.Reset()
+		ro.aggMutex.Unlock()
 	}
 
 	nFails, nMetrics := ro.failMetrics.Len(), ro.metrics.Len()
@@ -192,6 +193,8 @@ func (ro *RunningOutput) write(metrics []telegraf.Metric) error {
 	if nMetrics == 0 {
 		return nil
 	}
+	ro.writeMutex.Lock()
+	defer ro.writeMutex.Unlock()
 	start := time.Now()
 	err := ro.Output.Write(metrics)
 	elapsed := time.Since(start)
diff --git a/output.go b/output.go
index 39b371ac4..2421048f0 100644
--- a/output.go
+++ b/output.go
@@ -13,9 +13,26 @@ type Output interface {
 	Write(metrics []Metric) error
 }
 
+// AggregatingOutput adds aggregating functionality to an Output.  May be used
+// if the Output only accepts a fixed set of aggregations over a time period.
+// These functions may be called concurrently to the Write function.
 type AggregatingOutput interface {
+	// Connect to the Output
+	Connect() error
+	// Close any connections to the Output
+	Close() error
+	// Description returns a one-sentence description on the Output
+	Description() string
+	// SampleConfig returns the default configuration of the Output
+	SampleConfig() string
+	// Write takes in group of points to be written to the Output
+	Write(metrics []Metric) error
+
+	// Add the metric to the aggregator
 	Add(in Metric)
+	// Push returns the aggregated metrics and is called every flush interval.
 	Push() []Metric
+	// Reset signals the the aggregator period is completed.
 	Reset()
 }
 
@@ -30,6 +47,7 @@ type ServiceOutput interface {
 	SampleConfig() string
 	// Write takes in group of points to be written to the Output
 	Write(metrics []Metric) error
+
 	// Start the "service" that will provide an Output
 	Start() error
 	// Stop the "service" that will provide an Output