Add SerializeBatch method to the Serializer interface (#4107)

docs/DATA_FORMATS_OUTPUT.md

@@ -1,35 +1,15 @@
-# Telegraf Output Data Formats
+# Output Data Formats
 
-Telegraf is able to serialize metrics into the following output data formats:
+In addition to output specific data formats, Telegraf supports a set of
+standard data formats that may be selected from when configuring many output
+plugins.
 
 1. [InfluxDB Line Protocol](#influx)
 1. [JSON](#json)
 1. [Graphite](#graphite)
 
-Telegraf metrics, like InfluxDB
-[points](https://docs.influxdata.com/influxdb/latest/concepts/glossary/#point),
-are a combination of four basic parts:
-
-1. Measurement Name
-1. Tags
-1. Fields
-1. Timestamp
-
-In InfluxDB line protocol, these 4 parts are easily defined in textual form:
-
-```
-measurement_name[,tag1=val1,...]  field1=val1[,field2=val2,...]  [timestamp]
-```
-
-For Telegraf outputs that write textual data (such as `kafka`, `mqtt`, and `file`),
-InfluxDB line protocol was originally the only available output format. But now
-we are normalizing telegraf metric "serializers" into a
-[plugin-like interface](https://github.com/influxdata/telegraf/tree/master/plugins/serializers)
-across all output plugins that can support it.
-You will be able to identify a plugin that supports different data formats
-by the presence of a `data_format`
-config option, for example, in the `file` output plugin:
-
+You will be able to identify the plugins with support by the presence of a
+`data_format` config option, for example, in the `file` output plugin:
 ```toml
 [[outputs.file]]
   ## Files to write to, "stdout" is a specially handled file.
@@ -40,22 +20,16 @@ config option, for example, in the `file` output plugin:
   ## more about them here:
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
   data_format = "influx"
-
-  ## Additional configuration options go here
 ```
 
-Each data_format has an additional set of configuration options available, which
-I'll go over below.
+## Influx
 
-# Influx:
-
-The `influx` format outputs data as
+The `influx` data format outputs metrics using
 [InfluxDB Line Protocol](https://docs.influxdata.com/influxdb/latest/write_protocols/line_protocol_tutorial/).
-This is the recommended format to use unless another format is required for
+This is the recommended format unless another format is required for
 interoperability.
 
-### Influx Configuration:
-
+### Influx Configuration
 ```toml
 [[outputs.file]]
   ## Files to write to, "stdout" is a specially handled file.
@@ -82,7 +56,7 @@ interoperability.
   # influx_uint_support = false
 ```
 
-# Graphite:
+## Graphite
 
 The Graphite data format translates Telegraf metrics into _dot_ buckets. A
 template can be specified for the output of Telegraf metrics into Graphite
@@ -115,7 +89,7 @@ tars.cpu-total.us-east-1.cpu.usage_idle 98.09 1455320690
 Fields with string values will be skipped.  Boolean fields will be converted
 to 1 (true) or 0 (false).
 
-### Graphite Configuration:
+### Graphite Configuration
 
 ```toml
 [[outputs.file]]
@@ -134,27 +108,63 @@ to 1 (true) or 0 (false).
   template = "host.tags.measurement.field"
 ```
 
-# JSON:
+## JSON
 
-The JSON data format serialized Telegraf metrics in json format. The format is:
+The JSON output data format output for a single metric is in the
+form:
+```json
+{
+    "fields": {
+        "field_1": 30,
+        "field_2": 4,
+        "field_N": 59,
+        "n_images": 660
+    },
+    "name": "docker",
+    "tags": {
+        "host": "raynor"
+    },
+    "timestamp": 1458229140
+}
+```
 
+When an output plugin needs to emit multiple metrics at one time, it may use
+the batch format.  The use of batch format is determined by the plugin,
+reference the documentation for the specific plugin.
 ```json
 {
-   "fields":{
-      "field_1":30,
-      "field_2":4,
-      "field_N":59,
-      "n_images":660
-   },
-   "name":"docker",
-   "tags":{
-      "host":"raynor"
-   },
-   "timestamp":1458229140
+    "metrics": [
+        {
+            "fields": {
+                "field_1": 30,
+                "field_2": 4,
+                "field_N": 59,
+                "n_images": 660
+            },
+            "name": "docker",
+            "tags": {
+                "host": "raynor"
+            },
+            "timestamp": 1458229140
+        },
+        {
+            "fields": {
+                "field_1": 30,
+                "field_2": 4,
+                "field_N": 59,
+                "n_images": 660
+            },
+            "name": "docker",
+            "tags": {
+                "host": "raynor"
+            },
+            "timestamp": 1458229140
+        }
+    ]
 }
 ```
 
-### JSON Configuration:
+### JSON Configuration
 
 ```toml
 [[outputs.file]]
@@ -166,14 +176,9 @@ The JSON data format serialized Telegraf metrics in json format. The format is:
   ## more about them here:
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
   data_format = "json"
-  json_timestamp_units = "1ns"
-```
 
-By default, the timestamp that is output in JSON data format serialized Telegraf
-metrics is in seconds. The precision of this timestamp can be adjusted for any output
-by adding the optional `json_timestamp_units` parameter to the configuration for
-that output. This parameter can be used to set the timestamp units to  nanoseconds (`ns`),
-microseconds (`us` or `µs`), milliseconds (`ms`), or seconds (`s`). Note that this
-parameter will be truncated to the nearest power of 10 that, so if the `json_timestamp_units`
-are set to `15ms` the timestamps for the JSON format serialized Telegraf metrics will be
-output in hundredths of a second (`10ms`).
+  ## The resolution to use for the metric timestamp.  Must be a duration string
+  ## such as "1ns", "1us", "1ms", "10ms", "1s".  Durations are truncated to
+  ## the power of 10 less than the specified units.
+  json_timestamp_units = "1s"
+```

plugins/outputs/influxdb/udp_test.go

@@ -66,13 +66,18 @@ func (d *MockDialer) DialContext(ctx context.Context, network string, address st
 }
 
 type MockSerializer struct {
-	SerializeF func(metric telegraf.Metric) ([]byte, error)
+	SerializeF      func(metric telegraf.Metric) ([]byte, error)
+	SerializeBatchF func(metrics []telegraf.Metric) ([]byte, error)
 }
 
 func (s *MockSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
 	return s.SerializeF(metric)
 }
 
+func (s *MockSerializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
+	return s.SerializeBatchF(metrics)
+}
+
 func TestUDP_NewUDPClientNoURL(t *testing.T) {
 	config := &influxdb.UDPConfig{}
 	_, err := influxdb.NewUDPClient(config)

plugins/serializers/graphite/graphite.go

@@ -1,6 +1,7 @@
 package graphite
 
 import (
+	"bytes"
 	"fmt"
 	"math"
 	"regexp"
@@ -60,6 +61,21 @@ func (s *GraphiteSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
 	return out, nil
 }
 
+func (s *GraphiteSerializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
+	var batch bytes.Buffer
+	for _, m := range metrics {
+		buf, err := s.Serialize(m)
+		if err != nil {
+			return nil, err
+		}
+		_, err = batch.Write(buf)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return batch.Bytes(), nil
+}
+
 func formatValue(value interface{}) string {
 	switch v := value.(type) {
 	case string:

plugins/serializers/graphite/graphite_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/metric"
 )
 
@@ -577,3 +578,32 @@ func TestClean(t *testing.T) {
 		})
 	}
 }
+
+func TestSerializeBatch(t *testing.T) {
+	now := time.Unix(1234567890, 0)
+	tests := []struct {
+		name        string
+		metric_name string
+		tags        map[string]string
+		fields      map[string]interface{}
+		expected    string
+	}{
+		{
+			"Base metric",
+			"cpu",
+			map[string]string{"host": "localhost"},
+			map[string]interface{}{"usage_busy": float64(8.5)},
+			"localhost.cpu.usage_busy 8.5 1234567890\nlocalhost.cpu.usage_busy 8.5 1234567890\n",
+		},
+	}
+
+	s := GraphiteSerializer{}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			m, err := metric.New(tt.metric_name, tt.tags, tt.fields, now)
+			assert.NoError(t, err)
+			actual, _ := s.SerializeBatch([]telegraf.Metric{m, m})
+			require.Equal(t, tt.expected, string(actual))
+		})
+	}
+}

plugins/serializers/influx/influx.go

@@ -102,6 +102,17 @@ func (s *Serializer) Serialize(m telegraf.Metric) ([]byte, error) {
 	return out, nil
 }
 
+func (s *Serializer) SerializeBatch(metrics []telegraf.Metric) ([]byte, error) {
+	var batch bytes.Buffer
+	for _, m := range metrics {
+		_, err := s.Write(&batch, m)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return batch.Bytes(), nil
+}
+
 func (s *Serializer) Write(w io.Writer, m telegraf.Metric) (int, error) {
 	err := s.writeMetric(w, m)
 	return s.bytesWritten, err

plugins/serializers/influx/influx_test.go

@@ -447,3 +447,24 @@ func BenchmarkSerializer(b *testing.B) {
 		})
 	}
 }
+
+func TestSerialize_SerializeBatch(t *testing.T) {
+	m := MustMetric(
+		metric.New(
+			"cpu",
+			map[string]string{},
+			map[string]interface{}{
+				"value": 42.0,
+			},
+			time.Unix(0, 0),
+		),
+	)
+
+	metrics := []telegraf.Metric{m, m}
+
+	serializer := NewSerializer()
+	serializer.SetFieldSortOrder(SortFields)
+	output, err := serializer.SerializeBatch(metrics)
+	require.NoError(t, err)
+	require.Equal(t, []byte("cpu value=42 0\ncpu value=42 0\n"), output)
+}