Add entity-body compression to http output (#4807)

plugins/outputs/http/README.md

@@ -44,4 +44,8 @@ data formats.  For data_formats that support batching, metrics are sent in batch
   # [outputs.http.headers]
   #   # Should be set manually to "application/json" for json data_format
   #   Content-Type = "text/plain; charset=utf-8"
+
+  ## HTTP Content-Encoding for write request body, can be set to "gzip" to
+  ## compress body or "identity" to apply no encoding.
+  # content_encoding = "identity"
 ```

plugins/outputs/http/http.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"net/http"
 	"strings"
@@ -55,6 +56,10 @@ var sampleConfig = `
   # [outputs.http.headers]
   #   # Should be set manually to "application/json" for json data_format
   #   Content-Type = "text/plain; charset=utf-8"
+
+  ## HTTP Content-Encoding for write request body, can be set to "gzip" to
+  ## compress body or "identity" to apply no encoding.
+  # content_encoding = "identity"
 `
 
 const (
@@ -64,16 +69,17 @@ const (
 )
 
 type HTTP struct {
-	URL          string            `toml:"url"`
-	Timeout      internal.Duration `toml:"timeout"`
-	Method       string            `toml:"method"`
-	Username     string            `toml:"username"`
-	Password     string            `toml:"password"`
-	Headers      map[string]string `toml:"headers"`
-	ClientID     string            `toml:"client_id"`
-	ClientSecret string            `toml:"client_secret"`
-	TokenURL     string            `toml:"token_url"`
-	Scopes       []string          `toml:"scopes"`
+	URL             string            `toml:"url"`
+	Timeout         internal.Duration `toml:"timeout"`
+	Method          string            `toml:"method"`
+	Username        string            `toml:"username"`
+	Password        string            `toml:"password"`
+	Headers         map[string]string `toml:"headers"`
+	ClientID        string            `toml:"client_id"`
+	ClientSecret    string            `toml:"client_secret"`
+	TokenURL        string            `toml:"token_url"`
+	Scopes          []string          `toml:"scopes"`
+	ContentEncoding string            `toml:"content_encoding"`
 	tls.ClientConfig
 
 	client     *http.Client
@@ -162,7 +168,17 @@ func (h *HTTP) Write(metrics []telegraf.Metric) error {
 }
 
 func (h *HTTP) write(reqBody []byte) error {
-	req, err := http.NewRequest(h.Method, h.URL, bytes.NewBuffer(reqBody))
+	var reqBodyBuffer io.Reader = bytes.NewBuffer(reqBody)
+
+	var err error
+	if h.ContentEncoding == "gzip" {
+		reqBodyBuffer, err = internal.CompressWithGzip(reqBodyBuffer)
+		if err != nil {
+			return err
+		}
+	}
+
+	req, err := http.NewRequest(h.Method, h.URL, reqBodyBuffer)
 	if err != nil {
 		return err
 	}
@@ -172,6 +188,9 @@ func (h *HTTP) write(reqBody []byte) error {
 	}
 
 	req.Header.Set("Content-Type", defaultContentType)
+	if h.ContentEncoding == "gzip" {
+		req.Header.Set("Content-Encoding", "gzip")
+	}
 	for k, v := range h.Headers {
 		req.Header.Set(k, v)
 	}

plugins/outputs/http/http_test.go

@@ -1,7 +1,9 @@
 package http
 
 import (
+	"compress/gzip"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -227,6 +229,66 @@ func TestContentType(t *testing.T) {
 	}
 }
 
+func TestContentEncodingGzip(t *testing.T) {
+	ts := httptest.NewServer(http.NotFoundHandler())
+	defer ts.Close()
+
+	u, err := url.Parse(fmt.Sprintf("http://%s", ts.Listener.Addr().String()))
+	require.NoError(t, err)
+
+	tests := []struct {
+		name     string
+		plugin   *HTTP
+		payload  string
+		expected string
+	}{
+		{
+			name: "default is no content encoding",
+			plugin: &HTTP{
+				URL: u.String(),
+			},
+			expected: "",
+		},
+		{
+			name: "overwrite content_encoding",
+			plugin: &HTTP{
+				URL:             u.String(),
+				ContentEncoding: "gzip",
+			},
+			expected: "gzip",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ts.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				require.Equal(t, tt.expected, r.Header.Get("Content-Encoding"))
+
+				body := r.Body
+				var err error
+				if r.Header.Get("Content-Encoding") == "gzip" {
+					body, err = gzip.NewReader(r.Body)
+					require.NoError(t, err)
+				}
+
+				payload, err := ioutil.ReadAll(body)
+				require.NoError(t, err)
+				require.Contains(t, string(payload), "cpu value=42")
+
+				w.WriteHeader(http.StatusNoContent)
+			})
+
+			serializer := influx.NewSerializer()
+			tt.plugin.SetSerializer(serializer)
+			err = tt.plugin.Connect()
+			require.NoError(t, err)
+
+			err = tt.plugin.Write([]telegraf.Metric{getMetric()})
+			require.NoError(t, err)
+		})
+	}
+}
+
 func TestBasicAuth(t *testing.T) {
 	ts := httptest.NewServer(http.NotFoundHandler())
 	defer ts.Close()