Make the API client's httpClient more pluggable (#2926)

api/api.go

@@ -168,6 +168,9 @@ type Config struct {
 	// Datacenter to use. If not provided, the default agent datacenter is used.
 	Datacenter string
 
+	// Transport is the Transport to use for the http client.
+	Transport *http.Transport
+
 	// HttpClient is the client to use. Default will be
 	// used if not provided.
 	HttpClient *http.Client
@@ -239,9 +242,7 @@ func defaultConfig(transportFn func() *http.Transport) *Config {
 	config := &Config{
 		Address: "127.0.0.1:8500",
 		Scheme:  "http",
-		HttpClient: &http.Client{
-			Transport: transportFn(),
-		},
+		Transport: transportFn(),
 	}
 
 	if addr := os.Getenv(HTTPAddrEnvName); addr != "" {
@@ -364,6 +365,10 @@ func NewClient(config *Config) (*Client, error) {
 		config.Scheme = defConfig.Scheme
 	}
 
+	if config.Transport == nil {
+		config.Transport = defConfig.Transport
+	}
+
 	if config.HttpClient == nil {
 		config.HttpClient = defConfig.HttpClient
 	}
@@ -392,17 +397,14 @@ func NewClient(config *Config) (*Client, error) {
 		config.TLSConfig.InsecureSkipVerify = defConfig.TLSConfig.InsecureSkipVerify
 	}
 
-	tlsClientConfig, err := SetupTLSConfig(&config.TLSConfig)
-
-	// We don't expect this to fail given that we aren't
-	// parsing any of the input, but we panic just in case
-	// since this doesn't have an error return.
-	if err != nil {
-		return nil, err
+	if config.HttpClient == nil {
+		var err error
+		config.HttpClient, err = NewHttpClient(config.Transport, config.TLSConfig)
+		if err != nil {
+			return nil, err
+		}
 	}
 
-	config.HttpClient.Transport.(*http.Transport).TLSClientConfig = tlsClientConfig
-
 	parts := strings.SplitN(config.Address, "://", 2)
 	if len(parts) == 2 {
 		switch parts[0] {
@@ -429,6 +431,23 @@ func NewClient(config *Config) (*Client, error) {
 	return client, nil
 }
 
+// NewHttpClient returns an http client configured with the given Transport and TLS
+// config.
+func NewHttpClient(transport *http.Transport, tlsConf TLSConfig) (*http.Client, error) {
+	tlsClientConfig, err := SetupTLSConfig(&tlsConf)
+
+	if err != nil {
+		return nil, err
+	}
+
+	transport.TLSClientConfig = tlsClientConfig
+	client := &http.Client{
+		Transport: transport,
+	}
+
+	return client, nil
+}
+
 // request is used to help build up a request
 type request struct {
 	config *Config

api/api_test.go

@@ -10,11 +10,11 @@ import (
 	"path/filepath"
 	"reflect"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/hashicorp/consul/testutil"
-	"strings"
 )
 
 type configCallback func(c *Config)
@@ -140,11 +140,11 @@ func TestDefaultConfig_env(t *testing.T) {
 
 		// Use keep alives as a check for whether pooling is on or off.
 		if pooled := i == 0; pooled {
-			if config.HttpClient.Transport.(*http.Transport).DisableKeepAlives != false {
+			if config.Transport.DisableKeepAlives != false {
 				t.Errorf("expected keep alives to be enabled")
 			}
 		} else {
-			if config.HttpClient.Transport.(*http.Transport).DisableKeepAlives != true {
+			if config.Transport.DisableKeepAlives != true {
 				t.Errorf("expected keep alives to be disabled")
 			}
 		}