Transport: Add support for global request headers

    hdr := http.Header{}
      hdr.Set("Accept", "application/yaml")
      hdr.Set("Authorization", "Bearer 46ToAxZ2ZGZCaDhEVVNJQ0J1dUYzdGZxa1BB")

    es, err := elasticsearch.NewClient(
      elasticsearch.Config{
        Header: hdr,
      },
    )

    res, _ := es.Info()
    fmt.Println(res)

    # [200 OK] ---
    # name: "es1"
    # ...

Related:

* #136
* #84
* #106 (comment)

(cherry picked from commit 3f39d54)

Author: karmi

elasticsearch.go

@@ -37,6 +37,8 @@ type Config struct {
 	CloudID string // Endpoint for the Elastic Service (https://elastic.co/cloud).
 	APIKey  string // Base64-encoded token for authorization; if set, overrides username and password.
 
+	Header http.Header // Global HTTP request header.
+
 	// PEM-encoded certificate authorities.
 	// When set, an empty certificate pool will be created, and the certificates will be appended to it.
 	// The option is only valid when the transport is not specified, or when it's http.Transport.
@@ -139,6 +141,7 @@ func NewClient(cfg Config) (*Client, error) {
 		Password: cfg.Password,
 		APIKey:   cfg.APIKey,
 
+		Header: cfg.Header,
 		CACert: cfg.CACert,
 
 		RetryOnStatus:        cfg.RetryOnStatus,

estransport/estransport.go

@@ -54,6 +54,7 @@ type Config struct {
 	Password string
 	APIKey   string
 
+	Header http.Header
 	CACert []byte
 
 	RetryOnStatus        []int
@@ -83,6 +84,7 @@ type Client struct {
 	username string
 	password string
 	apikey   string
+	header   http.Header
 
 	retryOnStatus         []int
 	disableRetry          bool
@@ -144,6 +146,7 @@ func New(cfg Config) (*Client, error) {
 		username: cfg.Username,
 		password: cfg.Password,
 		apikey:   cfg.APIKey,
+		header:   cfg.Header,
 
 		retryOnStatus:         cfg.RetryOnStatus,
 		disableRetry:          cfg.DisableRetry,
@@ -205,6 +208,7 @@ func (c *Client) Perform(req *http.Request) (*http.Response, error) {
 
 	// Update request
 	c.setReqUserAgent(req)
+	c.setReqGlobalHeader(req)
 
 	if req.Body != nil && req.Body != http.NoBody && req.GetBody == nil {
 		if !c.disableRetry || (c.logger != nil && c.logger.RequestBodyEnabled()) {
@@ -376,6 +380,19 @@ func (c *Client) setReqUserAgent(req *http.Request) *http.Request {
 	return req
 }
 
+func (c *Client) setReqGlobalHeader(req *http.Request) *http.Request {
+	if len(c.header) > 0 {
+		for k, v := range c.header {
+			if req.Header.Get(k) != k {
+				for _, vv := range v {
+					req.Header.Add(k, vv)
+				}
+			}
+		}
+	}
+	return req
+}
+
 func (c *Client) logRoundTrip(
 	req *http.Request,
 	res *http.Response,

estransport/estransport_benchmark_test.go

@@ -53,4 +53,23 @@ func BenchmarkTransport(b *testing.B) {
 			}
 		}
 	})
+
+	b.Run("Headers", func(b *testing.B) {
+		hdr := http.Header{}
+		hdr.Set("Accept", "application/yaml")
+
+		for i := 0; i < b.N; i++ {
+			tp, _ := estransport.New(estransport.Config{
+				URLs:      []*url.URL{{Scheme: "http", Host: "foo"}},
+				Header:    hdr,
+				Transport: newFakeTransport(b),
+			})
+
+			req, _ := http.NewRequest("GET", "/abc", nil)
+			_, err := tp.Perform(req)
+			if err != nil {
+				b.Fatalf("Unexpected error: %s", err)
+			}
+		}
+	})
 }

estransport/estransport_integration_test.go

@@ -70,3 +70,31 @@ func TestTransportRetries(t *testing.T) {
 		})
 	}
 }
+
+func TestTransportHeaders(t *testing.T) {
+	u, _ := url.Parse("http://localhost:9200")
+
+	hdr := http.Header{}
+	hdr.Set("Accept", "application/yaml")
+
+	tp, _ := estransport.New(estransport.Config{
+		URLs:   []*url.URL{u},
+		Header: hdr,
+	})
+
+	req, _ := http.NewRequest("GET", "/", nil)
+	res, err := tp.Perform(req)
+	if err != nil {
+		t.Fatalf("Unexpected error: %s", err)
+	}
+	defer res.Body.Close()
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("Unexpected error: %s", err)
+	}
+
+	if !bytes.HasPrefix(body, []byte("---")) {
+		t.Errorf("Unexpected response body:\n%s", body)
+	}
+}

estransport/estransport_internal_test.go

@@ -339,6 +339,34 @@ func TestTransportPerform(t *testing.T) {
 		}
 	})
 
+	t.Run("Sets global HTTP request headers", func(t *testing.T) {
+		hdr := http.Header{}
+		hdr.Set("X-Foo", "bar")
+
+		tp, _ := New(Config{Header: hdr})
+
+		{
+			// Set the global HTTP header
+			req, _ := http.NewRequest("GET", "/abc", nil)
+			tp.setReqGlobalHeader(req)
+
+			if req.Header.Get("X-Foo") != "bar" {
+				t.Errorf("Unexpected global HTTP request header value: %s", req.Header.Get("X-Foo"))
+			}
+		}
+
+		{
+			// Do NOT overwrite an existing request header
+			req, _ := http.NewRequest("GET", "/abc", nil)
+			req.Header.Set("X-Foo", "baz")
+			tp.setReqGlobalHeader(req)
+
+			if req.Header.Get("X-Foo") != "baz" {
+				t.Errorf("Unexpected global HTTP request header value: %s", req.Header.Get("X-Foo"))
+			}
+		}
+	})
+
 	t.Run("Error No URL", func(t *testing.T) {
 		tp, _ := New(Config{
 			URLs: []*url.URL{},