Add valuecounter aggregator plugin (#3523)

README.md

@@ -282,6 +282,7 @@ formats may be used with input plugins supporting the `data_format` option:
 * [basicstats](./plugins/aggregators/basicstats)
 * [minmax](./plugins/aggregators/minmax)
 * [histogram](./plugins/aggregators/histogram)
+* [valuecounter](./plugins/aggregators/valuecounter)
 
 ## Output Plugins
 

plugins/aggregators/all/all.go

@@ -4,4 +4,5 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/aggregators/basicstats"
 	_ "github.com/influxdata/telegraf/plugins/aggregators/histogram"
 	_ "github.com/influxdata/telegraf/plugins/aggregators/minmax"
+	_ "github.com/influxdata/telegraf/plugins/aggregators/valuecounter"
 )

plugins/aggregators/valuecounter/README.md

+# ValueCounter Aggregator Plugin
+
+The valuecounter plugin counts the occurrence of values in fields and emits the
+counter once every 'period' seconds.
+
+A use case for the valuecounter plugin is when you are processing a HTTP access
+log (with the logparser input) and want to count the HTTP status codes.
+
+The fields which will be counted must be configured with the `fields`
+configuration directive. When no `fields` is provided the plugin will not count
+any fields. The results are emitted in fields in the format:
+`originalfieldname_fieldvalue = count`.
+
+Valuecounter only works on fields of the type int, bool or string. Float fields
+are being dropped to prevent the creating of too many fields.
+
+### Configuration:
+
+```toml
+[[aggregators.valuecounter]]
+  ## General Aggregator Arguments:
+  ## The period on which to flush & clear the aggregator.
+  period = "30s"
+  ## If true, the original metric will be dropped by the
+  ## aggregator and will not get sent to the output plugins.
+  drop_original = false
+  ## The fields for which the values will be counted
+  fields = ["status"]
+```
+
+### Measurements & Fields:
+
+- measurement1
+    - field_value1
+    - field_value2
+
+### Tags:
+
+No tags are applied by this aggregator.
+
+### Example Output:
+
+Example for parsing a HTTP access log.
+
+telegraf.conf:
+```
+[[inputs.logparser]]
+  files = ["/tmp/tst.log"]
+  [inputs.logparser.grok]
+    patterns = ['%{DATA:url:tag} %{NUMBER:response:string}']
+    measurement = "access"
+
+[[aggregators.valuecounter]]
+  namepass = ["access"]
+  fields = ["response"]
+```
+
+/tmp/tst.log
+```
+/some/path 200
+/some/path 401
+/some/path 200
+```
+
+```
+$ telegraf --config telegraf.conf --quiet
+
+access,url=/some/path,path=/tmp/tst.log,host=localhost.localdomain response="200" 1511948755991487011
+access,url=/some/path,path=/tmp/tst.log,host=localhost.localdomain response="401" 1511948755991522282
+access,url=/some/path,path=/tmp/tst.log,host=localhost.localdomain response="200" 1511948755991531697
+
+access,path=/tmp/tst.log,host=localhost.localdomain,url=/some/path response_200=2i,response_401=1i 1511948761000000000
+```

plugins/aggregators/valuecounter/valuecounter.go

+package valuecounter
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/aggregators"
+)
+
+type aggregate struct {
+	name       string
+	tags       map[string]string
+	fieldCount map[string]int
+}
+
+// ValueCounter an aggregation plugin
+type ValueCounter struct {
+	cache  map[uint64]aggregate
+	Fields []string
+}
+
+// NewValueCounter create a new aggregation plugin which counts the occurances
+// of fields and emits the count.
+func NewValueCounter() telegraf.Aggregator {
+	vc := &ValueCounter{}
+	vc.Reset()
+	return vc
+}
+
+var sampleConfig = `
+  ## General Aggregator Arguments:
+  ## The period on which to flush & clear the aggregator.
+  period = "30s"
+  ## If true, the original metric will be dropped by the
+  ## aggregator and will not get sent to the output plugins.
+  drop_original = false
+  ## The fields for which the values will be counted
+  fields = []
+`
+
+// SampleConfig generates a sample config for the ValueCounter plugin
+func (vc *ValueCounter) SampleConfig() string {
+	return sampleConfig
+}
+
+// Description returns the description of the ValueCounter plugin
+func (vc *ValueCounter) Description() string {
+	return "Count the occurance of values in fields."
+}
+
+// Add is run on every metric which passes the plugin
+func (vc *ValueCounter) Add(in telegraf.Metric) {
+	id := in.HashID()
+
+	// Check if the cache already has an entry for this metric, if not create it
+	if _, ok := vc.cache[id]; !ok {
+		a := aggregate{
+			name:       in.Name(),
+			tags:       in.Tags(),
+			fieldCount: make(map[string]int),
+		}
+		vc.cache[id] = a
+	}
+
+	// Check if this metric has fields which we need to count, if so increment
+	// the count.
+	for fk, fv := range in.Fields() {
+		for _, cf := range vc.Fields {
+			if fk == cf {
+				// Do not process float types to prevent memory from blowing up
+				switch fv.(type) {
+				default:
+					log.Printf("I! Valuecounter: Unsupported field type. " +
+						"Must be an int, string or bool. Ignoring.")
+					continue
+				case uint64, int64, string, bool:
+				}
+				fn := fmt.Sprintf("%v_%v", fk, fv)
+				vc.cache[id].fieldCount[fn]++
+			}
+		}
+	}
+}
+
+// Push emits the counters
+func (vc *ValueCounter) Push(acc telegraf.Accumulator) {
+	for _, agg := range vc.cache {
+		fields := map[string]interface{}{}
+
+		for field, count := range agg.fieldCount {
+			fields[field] = count
+		}
+
+		acc.AddFields(agg.name, fields, agg.tags)
+	}
+}
+
+// Reset the cache, executed after each push
+func (vc *ValueCounter) Reset() {
+	vc.cache = make(map[uint64]aggregate)
+}
+
+func init() {
+	aggregators.Add("valuecounter", func() telegraf.Aggregator {
+		return NewValueCounter()
+	})
+}

plugins/aggregators/valuecounter/valuecounter_test.go

+package valuecounter
+
+import (
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
+	"github.com/influxdata/telegraf/testutil"
+)
+
+// Create a valuecounter with config
+func NewTestValueCounter(fields []string) telegraf.Aggregator {
+	vc := &ValueCounter{
+		Fields: fields,
+	}
+	vc.Reset()
+
+	return vc
+}
+
+var m1, _ = metric.New("m1",
+	map[string]string{"foo": "bar"},
+	map[string]interface{}{
+		"status":    200,
+		"somefield": 20.1,
+		"foobar":    "bar",
+	},
+	time.Now(),
+)
+
+var m2, _ = metric.New("m1",
+	map[string]string{"foo": "bar"},
+	map[string]interface{}{
+		"status":    "OK",
+		"ignoreme":  "string",
+		"andme":     true,
+		"boolfield": false,
+	},
+	time.Now(),
+)
+
+func BenchmarkApply(b *testing.B) {
+	vc := NewTestValueCounter([]string{"status"})
+
+	for n := 0; n < b.N; n++ {
+		vc.Add(m1)
+		vc.Add(m2)
+	}
+}
+
+// Test basic functionality
+func TestBasic(t *testing.T) {
+	vc := NewTestValueCounter([]string{"status"})
+	acc := testutil.Accumulator{}
+
+	vc.Add(m1)
+	vc.Add(m2)
+	vc.Add(m1)
+	vc.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"status_200": 2,
+		"status_OK":  1,
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}
+
+// Test with multiple fields to count
+func TestMultipleFields(t *testing.T) {
+	vc := NewTestValueCounter([]string{"status", "somefield", "boolfield"})
+	acc := testutil.Accumulator{}
+
+	vc.Add(m1)
+	vc.Add(m2)
+	vc.Add(m2)
+	vc.Add(m1)
+	vc.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"status_200":      2,
+		"status_OK":       2,
+		"boolfield_false": 2,
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}
+
+// Test with a reset between two runs
+func TestWithReset(t *testing.T) {
+	vc := NewTestValueCounter([]string{"status"})
+	acc := testutil.Accumulator{}
+
+	vc.Add(m1)
+	vc.Add(m1)
+	vc.Add(m2)
+	vc.Push(&acc)
+
+	expectedFields := map[string]interface{}{
+		"status_200": 2,
+		"status_OK":  1,
+	}
+	expectedTags := map[string]string{
+		"foo": "bar",
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+
+	acc.ClearMetrics()
+	vc.Reset()
+
+	vc.Add(m2)
+	vc.Add(m2)
+	vc.Add(m1)
+	vc.Push(&acc)
+
+	expectedFields = map[string]interface{}{
+		"status_200": 1,
+		"status_OK":  2,
+	}
+	acc.AssertContainsTaggedFields(t, "m1", expectedFields, expectedTags)
+}