API-7853: add support for retry

add support for retry strategy

add unit tests for retry strategy

remove debug logs, add support for basic tokens, add docs for retry

Author: bkubiak

agent/api.go

@@ -15,6 +15,7 @@ type agentAPI interface {
 	UploadFile(string, []byte) (string, error)
 	SetCustomHost(string)
 	SetCustomHeader(string, string)
+	SetRetryStrategy(i.RetryStrategyFunc)
 }
 
 // API provides the API operation methods for making requests to Agent Chat API via Web API.

agent/api_test.go

@@ -358,6 +358,33 @@ func createMockedErrorResponder(t *testing.T, method string) func(req *http.Requ
 	}
 }
 
+func createMockedMultipleAuthErrorsResponder(t *testing.T, fails int) func(req *http.Request) *http.Response {
+	var n int
+
+	responseError := `{
+		"error": {
+			"type": "authentication",
+			"message": "Invalid access token"
+		}
+	}`
+
+	return func(req *http.Request) *http.Response {
+		n++
+		if n > fails {
+			return &http.Response{
+				StatusCode: http.StatusOK,
+				Body:       ioutil.NopCloser(bytes.NewBufferString(`{}`)),
+				Header:     make(http.Header),
+			}
+		}
+		return &http.Response{
+			StatusCode: http.StatusUnauthorized,
+			Body:       ioutil.NopCloser(bytes.NewBufferString(responseError)),
+			Header:     make(http.Header),
+		}
+	}
+}
+
 func verifyErrorResponse(method string, resp error, t *testing.T) {
 	if resp == nil {
 		t.Errorf("%v should fail", method)
@@ -1487,3 +1514,61 @@ func TestInvalidAuthorizationScheme(t *testing.T) {
 		t.Errorf("Err should not be nil")
 	}
 }
+
+func TestRetryStrategyAllFails(t *testing.T) {
+	client := NewTestClient(createMockedMultipleAuthErrorsResponder(t, 10))
+
+	api, err := agent.NewAPI(stubTokenGetter(authorization.BearerToken), client, "client_id")
+	if err != nil {
+		t.Errorf("API creation failed")
+	}
+
+	var retries uint
+	api.SetRetryStrategy(func(attempts uint, err error) bool {
+		if attempts < 3 {
+			retries++
+			return true
+		}
+
+		return false
+	})
+
+	err = api.Call("", nil, nil)
+	if err == nil {
+		t.Errorf("Err should not be nil")
+	}
+
+	if retries != 3 {
+		t.Errorf("Retries should be done 3 times")
+	}
+
+}
+
+func TestRetryStrategyLastSuccess(t *testing.T) {
+	client := NewTestClient(createMockedMultipleAuthErrorsResponder(t, 2))
+
+	api, err := agent.NewAPI(stubTokenGetter(authorization.BearerToken), client, "client_id")
+	if err != nil {
+		t.Errorf("API creation failed")
+	}
+
+	var retries uint
+	api.SetRetryStrategy(func(attempts uint, err error) bool {
+		if attempts < 3 {
+			retries++
+			return true
+		}
+
+		return false
+	})
+
+	err = api.Call("", nil, &struct{}{})
+	if err != nil {
+		t.Errorf("Err should be nil after 2 retries")
+	}
+
+	if retries != 2 {
+		t.Errorf("Retries should be done 2 times")
+	}
+
+}

configuration/api.go

@@ -12,6 +12,7 @@ import (
 type configurationAPI interface {
 	Call(string, interface{}, interface{}) error
 	SetCustomHost(string)
+	SetRetryStrategy(i.RetryStrategyFunc)
 }
 
 // API provides the API operation methods for making requests to Livechat Configuration API via Web API.

customer/api.go

@@ -14,6 +14,7 @@ type customerAPI interface {
 	Call(string, interface{}, interface{}) error
 	UploadFile(string, []byte) (string, error)
 	SetCustomHost(string)
+	SetRetryStrategy(i.RetryStrategyFunc)
 }
 
 // API provides the API operation methods for making requests to Customer Chat API via Web API.

internal/web_api.go

@@ -16,13 +16,22 @@ import (
 
 const apiVersion = "3.2"
 
+// RetryStrategyFunc is called by each API method if set to retry when handling an error.
+// If not set, there will be no retry at all.
+//
+// It accepts two arguments: attempts - number of sent requests (starting from 0)
+// and err - error as ErrAPI struct (with StatusCode and Details)
+// It returns info whether to retry the request.
+type RetryStrategyFunc func(attempts uint, err error) bool
+
 type api struct {
 	httpClient           *http.Client
 	clientID             string
 	tokenGetter          authorization.TokenGetter
 	httpRequestGenerator HTTPRequestGenerator
 	host                 string
 	customHeaders        http.Header
+	retryStrategy        RetryStrategyFunc
 }
 
 // HTTPRequestGenerator is called by each API method to generate api http url.
@@ -59,12 +68,9 @@ func (a *api) Call(action string, reqPayload interface{}, respPayload interface{
 	if err != nil {
 		return err
 	}
-	token := a.tokenGetter()
-	if token == nil {
-		return fmt.Errorf("couldn't get token")
-	}
-	if token.Type != authorization.BearerToken && token.Type != authorization.BasicToken {
-		return fmt.Errorf("unsupported token type")
+	token, err := a.getToken()
+	if err != nil {
+		return err
 	}
 
 	req, err := a.httpRequestGenerator(token, a.host, action)
@@ -93,6 +99,11 @@ func (a *api) SetCustomHeader(key, val string) {
 	a.customHeaders.Set(key, val)
 }
 
+// SetRetryStrategy allows to set a retry strategy that will be performed in every failed request
+func (a *api) SetRetryStrategy(f RetryStrategyFunc) {
+	a.retryStrategy = f
+}
+
 type fileUploadAPI struct{ *api }
 
 // NewAPIWithFileUpload returns ready to use raw API client with file upload functionality.
@@ -133,7 +144,7 @@ func (a *fileUploadAPI) UploadFile(filename string, file []byte) (string, error)
 	req.Body = ioutil.NopCloser(body)
 
 	req.Header.Set("Content-Type", writer.FormDataContentType())
-	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token.AccessToken))
+	req.Header.Set("Authorization", fmt.Sprintf("%s %s", token.Type, token.AccessToken))
 	req.Header.Set("User-agent", fmt.Sprintf("GO SDK Application %s", a.clientID))
 	req.Header.Set("X-Region", token.Region)
 
@@ -145,28 +156,59 @@ func (a *fileUploadAPI) UploadFile(filename string, file []byte) (string, error)
 }
 
 func (a *api) send(req *http.Request, respPayload interface{}) error {
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
-	bodyBytes, err := ioutil.ReadAll(resp.Body)
-	if resp.StatusCode != http.StatusOK {
-		apiErr := &api_errors.ErrAPI{}
-		if err := json.Unmarshal(bodyBytes, apiErr); err != nil {
-			return fmt.Errorf("couldn't unmarshal error response: %s (code: %d, raw body: %s)", err.Error(), resp.StatusCode, string(bodyBytes))
+	var attempts uint
+	var do func() error
+
+	do = func() error {
+		resp, err := a.httpClient.Do(req)
+		if err != nil {
+			return err
 		}
-		if apiErr.Error() == "" {
-			return fmt.Errorf("couldn't unmarshal error response (code: %d, raw body: %s)", resp.StatusCode, string(bodyBytes))
+		defer resp.Body.Close()
+		bodyBytes, err := ioutil.ReadAll(resp.Body)
+		if resp.StatusCode != http.StatusOK {
+			apiErr := &api_errors.ErrAPI{}
+			if err := json.Unmarshal(bodyBytes, apiErr); err != nil {
+				return fmt.Errorf("couldn't unmarshal error response: %s (code: %d, raw body: %s)", err.Error(), resp.StatusCode, string(bodyBytes))
+			}
+			if apiErr.Error() == "" {
+				return fmt.Errorf("couldn't unmarshal error response (code: %d, raw body: %s)", resp.StatusCode, string(bodyBytes))
+			}
+
+			if a.retryStrategy == nil || !a.retryStrategy(attempts, apiErr) {
+				return apiErr
+			}
+
+			token, err := a.getToken()
+			if err != nil {
+				return err
+			}
+
+			req.Header.Set("Authorization", fmt.Sprintf("%s %s", token.Type, token.AccessToken))
+			attempts++
+			return do()
+		}
+
+		if err != nil {
+			return err
 		}
-		return apiErr
+
+		return json.Unmarshal(bodyBytes, respPayload)
 	}
 
-	if err != nil {
-		return err
+	return do()
+}
+
+func (a *api) getToken() (*authorization.Token, error) {
+	token := a.tokenGetter()
+	if token == nil {
+		return nil, fmt.Errorf("couldn't get token")
+	}
+	if token.Type != authorization.BearerToken && token.Type != authorization.BasicToken {
+		return nil, fmt.Errorf("unsupported token type")
 	}
 
-	return json.Unmarshal(bodyBytes, respPayload)
+	return token, nil
 }
 
 // SetCustomHost allows to change API host address. This method is mostly for LiveChat internal testing and should not be used in production environments.