Add ability to override proxy from environment in http response (#3626)

plugins/inputs/http_response/http_response.go

@@ -20,6 +20,7 @@ import (
 // HTTPResponse struct
 type HTTPResponse struct {
 	Address             string
+	Proxy               string
 	Body                string
 	Method              string
 	ResponseTimeout     internal.Duration
@@ -49,6 +50,9 @@ var sampleConfig = `
   ## Server address (default http://localhost)
   # address = "http://localhost"
 
+  ## Set http_proxy (telegraf uses the system wide proxy settings if it's is not set)
+  # http_proxy = "http://localhost:8888"
+
   ## Set response_timeout (default 5 seconds)
   # response_timeout = "5s"
 
@@ -88,6 +92,22 @@ func (h *HTTPResponse) SampleConfig() string {
 // ErrRedirectAttempted indicates that a redirect occurred
 var ErrRedirectAttempted = errors.New("redirect")
 
+// Set the proxy. A configured proxy overwrites the system wide proxy.
+func getProxyFunc(http_proxy string) func(*http.Request) (*url.URL, error) {
+	if http_proxy == "" {
+		return http.ProxyFromEnvironment
+	}
+	proxyURL, err := url.Parse(http_proxy)
+	if err != nil {
+		return func(_ *http.Request) (*url.URL, error) {
+			return nil, errors.New("bad proxy: " + err.Error())
+		}
+	}
+	return func(r *http.Request) (*url.URL, error) {
+		return proxyURL, nil
+	}
+}
+
 // CreateHttpClient creates an http client which will timeout at the specified
 // timeout period and can follow redirects if specified
 func (h *HTTPResponse) createHttpClient() (*http.Client, error) {
@@ -98,7 +118,7 @@ func (h *HTTPResponse) createHttpClient() (*http.Client, error) {
 	}
 	client := &http.Client{
 		Transport: &http.Transport{
-			Proxy:             http.ProxyFromEnvironment,
+			Proxy:             getProxyFunc(h.Proxy),
 			DisableKeepAlives: true,
 			TLSClientConfig:   tlsCfg,
 		},