proxy support for http input (influxdata#8477)

plugins/common/proxy/proxy.go

@@ -0,0 +1,24 @@
+package proxy
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+)
+
+type HTTPProxy struct {
+	HTTPProxyURL string `toml:"http_proxy_url"`
+}
+
+type proxyFunc func(req *http.Request) (*url.URL, error)
+
+func (p *HTTPProxy) Proxy() (proxyFunc, error) {
+	if len(p.HTTPProxyURL) > 0 {
+		url, err := url.Parse(p.HTTPProxyURL)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing proxy url %q: %w", p.HTTPProxyURL, err)
+		}
+		return http.ProxyURL(url), nil
+	}
+	return http.ProxyFromEnvironment, nil
+}

plugins/inputs/http/README.md

@@ -34,6 +34,9 @@ The HTTP input plugin collects metrics from one or more HTTP(S) endpoints.  The
   # username = "username"
   # password = "pa$$word"
 
+  ## HTTP Proxy support
+  # http_proxy_url = ""
+
   ## Optional TLS Config
   # tls_ca = "/etc/telegraf/ca.pem"
   # tls_cert = "/etc/telegraf/cert.pem"

plugins/inputs/http/http.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/common/proxy"
 	"github.com/influxdata/telegraf/plugins/common/tls"
 	"github.com/influxdata/telegraf/plugins/inputs"
 	"github.com/influxdata/telegraf/plugins/parsers"
@@ -29,6 +30,8 @@ type HTTP struct {
 	Password string `toml:"password"`
 	tls.ClientConfig
 
+	proxy.HTTPProxy
+
 	// Absolute path to file with Bearer token
 	BearerToken string `toml:"bearer_token"`
 
@@ -70,6 +73,9 @@ var sampleConfig = `
   ## compress body or "identity" to apply no encoding.
   # content_encoding = "identity"
 
+  ## HTTP Proxy support
+  # http_proxy_url = ""
+
   ## Optional TLS Config
   # tls_ca = "/etc/telegraf/ca.pem"
   # tls_cert = "/etc/telegraf/cert.pem"
@@ -106,12 +112,19 @@ func (h *HTTP) Init() error {
 		return err
 	}
 
+	proxy, err := h.HTTPProxy.Proxy()
+	if err != nil {
+		return err
+	}
+
+	transport := &http.Transport{
+		TLSClientConfig: tlsCfg,
+		Proxy:           proxy,
+	}
+
 	h.client = &http.Client{
-		Transport: &http.Transport{
-			TLSClientConfig: tlsCfg,
-			Proxy:           http.ProxyFromEnvironment,
-		},
-		Timeout: h.Timeout.Duration,
+		Transport: transport,
+		Timeout:   h.Timeout.Duration,
 	}
 
 	// Set default as [200]