From 3c4e737f6bc4d5febd53a5be15da1695e1d15b47 Mon Sep 17 00:00:00 2001
From: Greg <2653109+glinton@users.noreply.github.com>
Date: Thu, 3 Jan 2019 13:06:56 -0700
Subject: [PATCH] Add example to topk readme. Fix defaults to skip loop (#5220)

---
 plugins/processors/topk/README.md | 33 +++++++++++++++++++++++++++++++
 plugins/processors/topk/topk.go   | 13 ++++++------
 2 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/plugins/processors/topk/README.md b/plugins/processors/topk/README.md
index 9c9e48af98943..15046991d7ff1 100644
--- a/plugins/processors/topk/README.md
+++ b/plugins/processors/topk/README.md
@@ -72,3 +72,36 @@ This processor does not add tags by default. But the setting `add_groupby_tag` w
 ### Fields:
 
 This processor does not add fields by default. But the settings `add_rank_fields` and `add_aggregation_fields` will add one or several fields if set to anything other than ""
+
+
+### Example
+**Config**
+```toml
+[[processors.topk]]
+  period = 20
+  k = 3
+  group_by = ["pid"]
+  fields = ["cpu_usage"]
+```
+
+**Output difference with topk**
+```diff
+< procstat,pid=2088,process_name=Xorg cpu_usage=7.296576662282613 1546473820000000000
+< procstat,pid=2780,process_name=ibus-engine-simple cpu_usage=0 1546473820000000000
+< procstat,pid=2554,process_name=gsd-sound cpu_usage=0 1546473820000000000
+< procstat,pid=3484,process_name=chrome cpu_usage=4.274300361942799 1546473820000000000
+< procstat,pid=2467,process_name=gnome-shell-calendar-server cpu_usage=0 1546473820000000000
+< procstat,pid=2525,process_name=gvfs-goa-volume-monitor cpu_usage=0 1546473820000000000
+< procstat,pid=2888,process_name=gnome-terminal-server cpu_usage=1.0224991500287577 1546473820000000000
+< procstat,pid=2454,process_name=ibus-x11 cpu_usage=0 1546473820000000000
+< procstat,pid=2564,process_name=gsd-xsettings cpu_usage=0 1546473820000000000
+< procstat,pid=12184,process_name=docker cpu_usage=0 1546473820000000000
+< procstat,pid=2432,process_name=pulseaudio cpu_usage=9.892858669796528 1546473820000000000
+---
+> procstat,pid=2432,process_name=pulseaudio cpu_usage=11.486933087507786 1546474120000000000
+> procstat,pid=2432,process_name=pulseaudio cpu_usage=10.056503212060552 1546474130000000000
+> procstat,pid=23620,process_name=chrome cpu_usage=2.098690278123081 1546474120000000000
+> procstat,pid=23620,process_name=chrome cpu_usage=17.52514619948493 1546474130000000000
+> procstat,pid=2088,process_name=Xorg cpu_usage=1.6016732172309973 1546474120000000000
+> procstat,pid=2088,process_name=Xorg cpu_usage=8.481040931533833 1546474130000000000
+```
diff --git a/plugins/processors/topk/topk.go b/plugins/processors/topk/topk.go
index df5d542e32679..c2244c6e32dad 100644
--- a/plugins/processors/topk/topk.go
+++ b/plugins/processors/topk/topk.go
@@ -43,8 +43,8 @@ func New() *TopK {
 	topk.Aggregation = "mean"
 	topk.GroupBy = []string{"*"}
 	topk.AddGroupByTag = ""
-	topk.AddRankFields = []string{""}
-	topk.AddAggregateFields = []string{""}
+	topk.AddRankFields = []string{}
+	topk.AddAggregateFields = []string{}
 
 	// Initialize cache
 	topk.Reset()
@@ -203,7 +203,9 @@ func (t *TopK) Apply(in ...telegraf.Metric) []telegraf.Metric {
 	if t.aggFieldSet == nil {
 		t.aggFieldSet = make(map[string]bool)
 		for _, f := range t.AddAggregateFields {
-			t.aggFieldSet[f] = true
+			if f != "" {
+				t.aggFieldSet[f] = true
+			}
 		}
 	}
 
@@ -279,7 +281,6 @@ func (t *TopK) push() []telegraf.Metric {
 
 	// Get the top K metrics for each field and add them to the return value
 	addedKeys := make(map[string]bool)
-	groupTag := t.AddGroupByTag
 	for _, field := range t.Fields {
 
 		// Sort the aggregations
@@ -288,9 +289,8 @@ func (t *TopK) push() []telegraf.Metric {
 		// Create a one dimensional list with the top K metrics of each key
 		for i, ag := range aggregations[0:min(t.K, len(aggregations))] {
 			// Check whether of not we need to add fields of tags to the selected metrics
-			if len(t.aggFieldSet) != 0 || len(t.rankFieldSet) != 0 || groupTag != "" {
+			if len(t.aggFieldSet) != 0 || len(t.rankFieldSet) != 0 || t.AddGroupByTag != "" {
 				for _, m := range t.cache[ag.groupbykey] {
-
 					// Add the aggregation final value if requested
 					_, addAggField := t.aggFieldSet[field]
 					if addAggField && m.HasField(field) {
@@ -330,7 +330,6 @@ func (t *TopK) push() []telegraf.Metric {
 
 // Function that generates the aggregation functions
 func (t *TopK) getAggregationFunction(aggOperation string) (func([]telegraf.Metric, []string) map[string]float64, error) {
-
 	// This is a function aggregates a set of metrics using a given aggregation function
 	var aggregator = func(ms []telegraf.Metric, fields []string, f func(map[string]float64, float64, string)) map[string]float64 {
 		agg := make(map[string]float64)