Add gzip content-encoding support to influxdb output (#2978)

plugins/outputs/influxdb/README.md

@@ -43,6 +43,9 @@ This plugin writes to [InfluxDB](https://www.influxdb.com) via HTTP or UDP.
 
   ## HTTP Proxy Config
   # http_proxy = "http://corporate.proxy:3128"
+
+  ## Compress each HTTP request payload using GZIP.
+  # content_encoding = "gzip"
 ```
 
 ### Required parameters:
@@ -67,3 +70,4 @@ to write to. Each URL should start with either `http://` or `udp://`
 * `ssl_key`: SSL key
 * `insecure_skip_verify`: Use SSL but skip chain & host verification (default: false)
 * `http_proxy`: HTTP Proxy URI
+* `content_encoding`: Compress each HTTP request payload using gzip if set to: "gzip"

plugins/outputs/influxdb/client/http.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"bytes"
+	"compress/gzip"
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
@@ -94,9 +95,8 @@ type HTTPConfig struct {
 	// Proxy URL should be of the form "http://host:port"
 	HTTPProxy string
 
-	// Gzip, if true, compresses each payload using gzip.
-	// TODO
-	// Gzip bool
+	// The content encoding mechanism to use for each request.
+	ContentEncoding string
 }
 
 // Response represents a list of statement results.
@@ -232,16 +232,24 @@ func (c *httpClient) makeWriteRequest(
 	if err != nil {
 		return nil, err
 	}
-	req.Header.Set("Content-Length", fmt.Sprint(contentLength))
-	// TODO
-	// if gzip {
-	// 	req.Header.Set("Content-Encoding", "gzip")
-	// }
+	if c.config.ContentEncoding == "gzip" {
+		req.Header.Set("Content-Encoding", "gzip")
+	} else {
+		req.Header.Set("Content-Length", fmt.Sprint(contentLength))
+	}
 	return req, nil
 }
 
 func (c *httpClient) makeRequest(uri string, body io.Reader) (*http.Request, error) {
-	req, err := http.NewRequest("POST", uri, body)
+	var req *http.Request
+	var err error
+	if c.config.ContentEncoding == "gzip" {
+		body, err = compressWithGzip(body)
+		if err != nil {
+			return nil, err
+		}
+	}
+	req, err = http.NewRequest("POST", uri, body)
 	if err != nil {
 		return nil, err
 	}
@@ -253,6 +261,20 @@ func (c *httpClient) makeRequest(uri string, body io.Reader) (*http.Request, err
 	return req, nil
 }
 
+func compressWithGzip(data io.Reader) (io.Reader, error) {
+	pr, pw := io.Pipe()
+	gw := gzip.NewWriter(pw)
+	var err error
+
+	go func() {
+		_, err = io.Copy(gw, data)
+		gw.Close()
+		pw.Close()
+	}()
+
+	return pr, err
+}
+
 func (c *httpClient) Close() error {
 	// Nothing to do.
 	return nil

plugins/outputs/influxdb/client/http_test.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"bytes"
+	"compress/gzip"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -341,3 +342,24 @@ func TestHTTPClient_Query_JSONDecodeError(t *testing.T) {
 	assert.Error(t, err)
 	assert.Contains(t, err.Error(), "json")
 }
+
+func TestGzipCompression(t *testing.T) {
+	influxLine := "cpu value=99\n"
+
+	// Compress the payload using GZIP.
+	payload := bytes.NewReader([]byte(influxLine))
+	compressed, err := compressWithGzip(payload)
+	assert.Nil(t, err)
+
+	// Decompress the compressed payload and make sure
+	// that its original value has not changed.
+	gr, err := gzip.NewReader(compressed)
+	assert.Nil(t, err)
+	gr.Close()
+
+	var uncompressed bytes.Buffer
+	_, err = uncompressed.ReadFrom(gr)
+	assert.Nil(t, err)
+
+	assert.Equal(t, []byte(influxLine), uncompressed.Bytes())
+}

plugins/outputs/influxdb/influxdb.go

@@ -34,6 +34,7 @@ type InfluxDB struct {
 	Timeout          internal.Duration
 	UDPPayload       int    `toml:"udp_payload"`
 	HTTPProxy        string `toml:"http_proxy"`
+	ContentEncoding  string `toml:"content_encoding"`
 
 	// Path to CA file
 	SSLCA string `toml:"ssl_ca"`
@@ -87,6 +88,9 @@ var sampleConfig = `
 
   ## HTTP Proxy Config
   # http_proxy = "http://corporate.proxy:3128"
+  
+  ## Compress each HTTP request payload using GZIP.
+  # content_encoding = "gzip"
 `
 
 // Connect initiates the primary connection to the range of provided URLs
@@ -121,13 +125,14 @@ func (i *InfluxDB) Connect() error {
 		default:
 			// If URL doesn't start with "udp", assume HTTP client
 			config := client.HTTPConfig{
-				URL:       u,
-				Timeout:   i.Timeout.Duration,
-				TLSConfig: tlsConfig,
-				UserAgent: i.UserAgent,
-				Username:  i.Username,
-				Password:  i.Password,
-				HTTPProxy: i.HTTPProxy,
+				URL:             u,
+				Timeout:         i.Timeout.Duration,
+				TLSConfig:       tlsConfig,
+				UserAgent:       i.UserAgent,
+				Username:        i.Username,
+				Password:        i.Password,
+				HTTPProxy:       i.HTTPProxy,
+				ContentEncoding: i.ContentEncoding,
 			}
 			wp := client.WriteParams{
 				Database:        i.Database,