From 516166881ea029c302682977372bbf66c145a9fa Mon Sep 17 00:00:00 2001
From: Mark Rechler <mrechler@bitly.com>
Date: Wed, 22 Apr 2015 15:35:06 -0400
Subject: [PATCH] add delete-gauges flag to support re-sending a value when
 there was no update

---
 statsdaemon.go      | 25 +++++++++++++++++++------
 statsdaemon_test.go | 35 +++++++++++++++++++++++++++++++++--
 2 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/statsdaemon.go b/statsdaemon.go
index d18594a..dc886ee 100644
--- a/statsdaemon.go
+++ b/statsdaemon.go
@@ -85,6 +85,7 @@ var (
 	flushInterval    = flag.Int64("flush-interval", 10, "Flush interval (seconds)")
 	debug            = flag.Bool("debug", false, "print statistics sent to graphite")
 	showVersion      = flag.Bool("version", false, "print version string")
+	deleteGauges     = flag.Bool("delete-gauges", true, "don't send values to graphite for inactive gauges, as opposed to sending the previous value")
 	persistCountKeys = flag.Int64("persist-count-keys", 60, "number of flush-intervals to persist count keys")
 	receiveCounter   = flag.String("receive-counter", "", "Metric name for total metrics received per interval")
 	percentThreshold = Percentiles{}
@@ -100,7 +101,7 @@ var (
 	In              = make(chan *Packet, MAX_UNPROCESSED_PACKETS)
 	counters        = make(map[string]int64)
 	gauges          = make(map[string]uint64)
-	trackedGauges   = make(map[string]uint64)
+	lastGaugeValue  = make(map[string]uint64)
 	timers          = make(map[string]Uint64Slice)
 	countInactivity = make(map[string]int64)
 	sets            = make(map[string][]string)
@@ -267,14 +268,26 @@ func processGauges(buffer *bytes.Buffer, now int64) int64 {
 	var num int64
 
 	for g, c := range gauges {
-		lastValue, ok := trackedGauges[g]
+		currentValue := c
+		lastValue, hasLastValue := lastGaugeValue[g]
+		var hasChanged bool
 
-		if ok && c == lastValue {
+		if c != math.MaxUint64 {
+			hasChanged = true
+		}
+
+		switch {
+		case hasChanged:
+			fmt.Fprintf(buffer, "%s %d %d\n", g, currentValue, now)
+			lastGaugeValue[g] = currentValue
+			gauges[g] = math.MaxUint64
+			num++
+		case hasLastValue && !hasChanged && !*deleteGauges:
+			fmt.Fprintf(buffer, "%s %d %d\n", g, lastValue, now)
+			num++
+		default:
 			continue
 		}
-		fmt.Fprintf(buffer, "%s %d %d\n", g, c, now)
-		trackedGauges[g] = c
-		num++
 	}
 	return num
 }
diff --git a/statsdaemon_test.go b/statsdaemon_test.go
index 65cdbe5..575fea0 100644
--- a/statsdaemon_test.go
+++ b/statsdaemon_test.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"flag"
 	"github.com/bmizerany/assert"
 	"math"
 	"math/rand"
@@ -384,19 +385,49 @@ func TestProcessTimers(t *testing.T) {
 
 func TestProcessGauges(t *testing.T) {
 	// Some data with expected mean of 20
+	flag.Set("delete-gauges", "false")
 	gauges = make(map[string]uint64)
+	gauges["gaugor"] = math.MaxUint64
+
+	now := int64(1418052649)
+
+	var buffer bytes.Buffer
+
+	num := processGauges(&buffer, now)
+	assert.Equal(t, num, int64(0))
+	assert.Equal(t, buffer.String(), "")
+
 	gauges["gaugor"] = 12345
+	num = processGauges(&buffer, now)
+	assert.Equal(t, num, int64(1))
+
+	gauges["gaugor"] = math.MaxUint64
+	num = processGauges(&buffer, now)
+	assert.Equal(t, buffer.String(), "gaugor 12345 1418052649\ngaugor 12345 1418052649\n")
+	assert.Equal(t, num, int64(1))
+}
+
+func TestProcessDeleteGauges(t *testing.T) {
+	// Some data with expected mean of 20
+	flag.Set("delete-gauges", "true")
+	gauges = make(map[string]uint64)
+	gauges["gaugordelete"] = math.MaxUint64
 
 	now := int64(1418052649)
 
 	var buffer bytes.Buffer
 
 	num := processGauges(&buffer, now)
+	assert.Equal(t, num, int64(0))
+	assert.Equal(t, buffer.String(), "")
+
+	gauges["gaugordelete"] = 12345
+	num = processGauges(&buffer, now)
 	assert.Equal(t, num, int64(1))
-	assert.Equal(t, buffer.String(), "gaugor 12345 1418052649\n")
 
-	gauges["gaugor"] = 12345
+	gauges["gaugordelete"] = math.MaxUint64
 	num = processGauges(&buffer, now)
+	assert.Equal(t, buffer.String(), "gaugordelete 12345 1418052649\n")
 	assert.Equal(t, num, int64(0))
 }