Add customroundtripper to httpclientconfig (open-telemetry#2085)

* added optional custom round tripper

* fixed comment

* returned error in roundtripper function

config/confighttp/confighttp.go

@@ -45,6 +45,9 @@ type HTTPClientSettings struct {
  // Additional headers attached to each HTTP request sent by the client.
  // Existing header values are overwritten if collision happens.
  Headers map[string]string `mapstructure:"headers,omitempty"`
+
+ // Custom Round Tripper to allow for individual components to intercept HTTP requests
+ CustomRoundTripper func(next http.RoundTripper) (http.RoundTripper, error)
 }
 
 func (hcs *HTTPClientSettings) ToClient() (*http.Client, error) {
@@ -71,6 +74,13 @@ func (hcs *HTTPClientSettings) ToClient() (*http.Client, error) {
  }
  }
 
+ if hcs.CustomRoundTripper != nil {
+ clientTransport, err = hcs.CustomRoundTripper(clientTransport)
+ if err != nil {
+ return nil, err
+ }
+ }
+
  return &http.Client{
  Transport: clientTransport,
  Timeout: hcs.Timeout,

config/confighttp/confighttp_test.go

@@ -15,6 +15,7 @@
 package confighttp
 
 import (
+ "errors"
  "fmt"
  "io/ioutil"
  "net/http"
@@ -31,19 +32,52 @@ import (
 )
 
 func TestAllHTTPClientSettings(t *testing.T) {
- hcs := &HTTPClientSettings{
- Endpoint: "localhost:1234",
- TLSSetting: configtls.TLSClientSetting{
- Insecure: false,
+ tests := []struct {
+ name string
+ settings HTTPClientSettings
+ shouldError bool
+ }{
+ {
+ name: "all_valid_settings",
+ settings: HTTPClientSettings{
+ Endpoint: "localhost:1234",
+ TLSSetting: configtls.TLSClientSetting{
+ Insecure: false,
+ },
+ ReadBufferSize: 1024,
+ WriteBufferSize: 512,
+ CustomRoundTripper: func(next http.RoundTripper) (http.RoundTripper, error) { return next, nil },
+ },
+ shouldError: false,
+ },
+ {
+ name: "error_round_tripper_returned",
+ settings: HTTPClientSettings{
+ Endpoint: "localhost:1234",
+ TLSSetting: configtls.TLSClientSetting{
+ Insecure: false,
+ },
+ ReadBufferSize: 1024,
+ WriteBufferSize: 512,
+ CustomRoundTripper: func(next http.RoundTripper) (http.RoundTripper, error) { return nil, errors.New("error") },
+ },
+ shouldError: true,
  },
- ReadBufferSize: 1024,
- WriteBufferSize: 512,
  }
- client, err := hcs.ToClient()
- assert.NoError(t, err)
- transport := client.Transport.(*http.Transport)
- assert.EqualValues(t, 1024, transport.ReadBufferSize)
- assert.EqualValues(t, 512, transport.WriteBufferSize)
+
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ client, err := test.settings.ToClient()
+ if test.shouldError {
+ assert.Error(t, err)
+ return
+ }
+ assert.NoError(t, err)
+ transport := client.Transport.(*http.Transport)
+ assert.EqualValues(t, 1024, transport.ReadBufferSize)
+ assert.EqualValues(t, 512, transport.WriteBufferSize)
+ })
+ }
 }
 
 func TestHTTPClientSettingsError(t *testing.T) {