Add support for CloudID

To facilitate connecting to the Elastic Service (https://elastic.co/cloud),
add a configuration option to take the CloudID (https://www.elastic.co/guide/en/cloud/current/ec-cloud-id.html),
which is parsed and transformed into a regular address.

doc.go

@@ -29,6 +29,8 @@ To configure the client, pass a Config object to the NewClient function:
 
 		elasticsearch.NewClient(cfg)
 
+When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses.
+
 See the elasticsearch_integration_test.go file and the _examples folder for more information.
 
 Call the Elasticsearch APIs by invoking the corresponding methods on the client:

elasticsearch.go

@@ -1,6 +1,7 @@
 package elasticsearch
 
 import (
+	"encoding/base64"
 	"errors"
 	"fmt"
 	"net/http"
@@ -28,6 +29,7 @@ type Config struct {
 	Username  string   // Username for HTTP Basic Authentication.
 	Password  string   // Password for HTTP Basic Authentication.
 
+	CloudID string // Endpoint for the Elastic Service (https://elastic.co/cloud).
 	Transport http.RoundTripper  // The HTTP transport object.
 	Logger    estransport.Logger // The logger object.
 }
@@ -61,13 +63,36 @@ func NewDefaultClient() (*Client, error) {
 // environment variable.
 //
 func NewClient(cfg Config) (*Client, error) {
+	var addrs []string
+
 	envAddrs := addrsFromEnvironment()
 
 	if len(envAddrs) > 0 && len(cfg.Addresses) > 0 {
 		return nil, errors.New("cannot create client: both ELASTICSEARCH_URL and Addresses are set")
 	}
 
-	addrs := append(envAddrs, cfg.Addresses...)
+	if len(envAddrs) > 0 && cfg.CloudID != "" {
+		return nil, errors.New("cannot create client: both ELASTICSEARCH_URL and CloudID are set")
+	}
+
+	if len(cfg.Addresses) > 0 && cfg.CloudID != "" {
+		return nil, errors.New("cannot create client: both Adresses and CloudID are set")
+	}
+
+	if cfg.CloudID != "" {
+		cloudAddrs, err := addrFromCloudID(cfg.CloudID)
+		if err != nil {
+			return nil, fmt.Errorf("cannot create client: cannot parse CloudID: %s", err)
+		}
+		addrs = append(addrs, cloudAddrs)
+	} else {
+		if len(envAddrs) > 0 {
+			addrs = append(envAddrs, envAddrs...)
+		}
+		if len(cfg.Addresses) > 0 {
+			addrs = append(envAddrs, cfg.Addresses...)
+		}
+	}
 
 	urls, err := addrsToURLs(addrs)
 	if err != nil {
@@ -127,3 +152,24 @@ func addrsToURLs(addrs []string) ([]*url.URL, error) {
 	}
 	return urls, nil
 }
+
+// addrFromCloudID extracts the Elasticsearch URL from CloudID.
+// See: https://www.elastic.co/guide/en/cloud/current/ec-cloud-id.html
+//
+func addrFromCloudID(input string) (string, error) {
+	var (
+		port   = 9243
+		scheme = "https://"
+	)
+
+	values := strings.Split(input, ":")
+	if len(values) != 2 {
+		return "", fmt.Errorf("unexpected format: %q", input)
+	}
+	data, err := base64.StdEncoding.DecodeString(values[1])
+	if err != nil {
+		return "", err
+	}
+	parts := strings.Split(string(data), "$")
+	return fmt.Sprintf("%s%s.%s:%d", scheme, parts[1], parts[0], port), nil
+}

elasticsearch_internal_test.go

@@ -3,6 +3,7 @@
 package elasticsearch
 
 import (
+	"encoding/base64"
 	"errors"
 	"net/http"
 	"net/url"
@@ -67,6 +68,44 @@ func TestClientConfiguration(t *testing.T) {
 		}
 	})
 
+	t.Run("With URL from environment and cfg.CloudID", func(t *testing.T) {
+		os.Setenv("ELASTICSEARCH_URL", "http://example.com")
+		defer func() { os.Setenv("ELASTICSEARCH_URL", "") }()
+
+		_, err := NewClient(Config{CloudID: "foobar="})
+		if err == nil {
+			t.Fatalf("Expected error, got: %v", err)
+		}
+		match, _ := regexp.MatchString("both .* are set", err.Error())
+		if !match {
+			t.Errorf("Expected error when addresses from environment and configuration are used together, got: %v", err)
+		}
+	})
+
+	t.Run("With cfg.Addresses and cfg.CloudID", func(t *testing.T) {
+		_, err := NewClient(Config{Addresses: []string{"http://localhost:8080//"}, CloudID: "foobar="})
+		if err == nil {
+			t.Fatalf("Expected error, got: %v", err)
+		}
+		match, _ := regexp.MatchString("both .* are set", err.Error())
+		if !match {
+			t.Errorf("Expected error when addresses from environment and configuration are used together, got: %v", err)
+		}
+	})
+
+	t.Run("With CloudID", func(t *testing.T) {
+		c, err := NewClient(Config{CloudID: "foo:YmFyLmNsb3VkLmVzLmlvJGFiYzEyMyRkZWY0NTY="})
+		if err != nil {
+			t.Fatalf("Unexpected error: %s", err)
+		}
+
+		u := c.Transport.(*estransport.Client).URLs()[0].String()
+
+		if u != "https://abc123.bar.cloud.es.io:9243" {
+			t.Errorf("Unexpected URL, want=https://abc123.bar.cloud.es.io:9243, got=%s", u)
+		}
+	})
+
 	t.Run("With invalid URL", func(t *testing.T) {
 		u := ":foo"
 		_, err := NewClient(Config{Addresses: []string{u}})
@@ -192,6 +231,45 @@ func TestAddrsToURLs(t *testing.T) {
 	}
 }
 
+func TestCloudID(t *testing.T) {
+	t.Run("Parse", func(t *testing.T) {
+		input := "name:" + base64.StdEncoding.EncodeToString([]byte("host$es$kibana"))
+		expected := "https://es.host:9243"
+
+		actual, err := addrFromCloudID(input)
+		if err != nil {
+			t.Errorf("Unexpected error: %s", err)
+		}
+		if actual != expected {
+			t.Errorf("Unexpected output, want=%q, got=%q", expected, actual)
+		}
+	})
+
+	t.Run("Invalid format", func(t *testing.T) {
+		input := "foobar"
+		_, err := addrFromCloudID(input)
+		if err == nil {
+			t.Errorf("Expected error for input %q, got %v", input, err)
+		}
+		match, _ := regexp.MatchString("unexpected format", err.Error())
+		if !match {
+			t.Errorf("Unexpected error string: %s", err)
+		}
+	})
+
+	t.Run("Invalid base64 value", func(t *testing.T) {
+		input := "foobar:xxxxx"
+		_, err := addrFromCloudID(input)
+		if err == nil {
+			t.Errorf("Expected error for input %q, got %v", input, err)
+		}
+		match, _ := regexp.MatchString("illegal base64 data", err.Error())
+		if !match {
+			t.Errorf("Unexpected error string: %s", err)
+		}
+	})
+}
+
 func TestVersion(t *testing.T) {
 	if Version == "" {
 		t.Error("Version is empty")