package autorest // Copyright 2017 Microsoft Corporation // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. import ( "fmt" "log" "math" "net/http" "strconv" "time" ) // Sender is the interface that wraps the Do method to send HTTP requests. // // The standard http.Client conforms to this interface. type Sender interface { Do(*http.Request) (*http.Response, error) } // SenderFunc is a method that implements the Sender interface. type SenderFunc func(*http.Request) (*http.Response, error) // Do implements the Sender interface on SenderFunc. func (sf SenderFunc) Do(r *http.Request) (*http.Response, error) { return sf(r) } // SendDecorator takes and possibily decorates, by wrapping, a Sender. Decorators may affect the // http.Request and pass it along or, first, pass the http.Request along then react to the // http.Response result. type SendDecorator func(Sender) Sender // CreateSender creates, decorates, and returns, as a Sender, the default http.Client. func CreateSender(decorators ...SendDecorator) Sender { return DecorateSender(&http.Client{}, decorators...) } // DecorateSender accepts a Sender and a, possibly empty, set of SendDecorators, which is applies to // the Sender. Decorators are applied in the order received, but their affect upon the request // depends on whether they are a pre-decorator (change the http.Request and then pass it along) or a // post-decorator (pass the http.Request along and react to the results in http.Response). func DecorateSender(s Sender, decorators ...SendDecorator) Sender { for _, decorate := range decorators { s = decorate(s) } return s } // Send sends, by means of the default http.Client, the passed http.Request, returning the // http.Response and possible error. It also accepts a, possibly empty, set of SendDecorators which // it will apply the http.Client before invoking the Do method. // // Send is a convenience method and not recommended for production. Advanced users should use // SendWithSender, passing and sharing their own Sender (e.g., instance of http.Client). // // Send will not poll or retry requests. func Send(r *http.Request, decorators ...SendDecorator) (*http.Response, error) { return SendWithSender(&http.Client{}, r, decorators...) } // SendWithSender sends the passed http.Request, through the provided Sender, returning the // http.Response and possible error. It also accepts a, possibly empty, set of SendDecorators which // it will apply the http.Client before invoking the Do method. // // SendWithSender will not poll or retry requests. func SendWithSender(s Sender, r *http.Request, decorators ...SendDecorator) (*http.Response, error) { return DecorateSender(s, decorators...).Do(r) } // AfterDelay returns a SendDecorator that delays for the passed time.Duration before // invoking the Sender. The delay may be terminated by closing the optional channel on the // http.Request. If canceled, no further Senders are invoked. func AfterDelay(d time.Duration) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { if !DelayForBackoff(d, 0, r.Cancel) { return nil, fmt.Errorf("autorest: AfterDelay canceled before full delay") } return s.Do(r) }) } } // AsIs returns a SendDecorator that invokes the passed Sender without modifying the http.Request. func AsIs() SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { return s.Do(r) }) } } // DoCloseIfError returns a SendDecorator that first invokes the passed Sender after which // it closes the response if the passed Sender returns an error and the response body exists. func DoCloseIfError() SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { resp, err := s.Do(r) if err != nil { Respond(resp, ByDiscardingBody(), ByClosing()) } return resp, err }) } } // DoErrorIfStatusCode returns a SendDecorator that emits an error if the response StatusCode is // among the set passed. Since these are artificial errors, the response body may still require // closing. func DoErrorIfStatusCode(codes ...int) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { resp, err := s.Do(r) if err == nil && ResponseHasStatusCode(resp, codes...) { err = NewErrorWithResponse("autorest", "DoErrorIfStatusCode", resp, "%v %v failed with %s", resp.Request.Method, resp.Request.URL, resp.Status) } return resp, err }) } } // DoErrorUnlessStatusCode returns a SendDecorator that emits an error unless the response // StatusCode is among the set passed. Since these are artificial errors, the response body // may still require closing. func DoErrorUnlessStatusCode(codes ...int) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { resp, err := s.Do(r) if err == nil && !ResponseHasStatusCode(resp, codes...) { err = NewErrorWithResponse("autorest", "DoErrorUnlessStatusCode", resp, "%v %v failed with %s", resp.Request.Method, resp.Request.URL, resp.Status) } return resp, err }) } } // DoPollForStatusCodes returns a SendDecorator that polls if the http.Response contains one of the // passed status codes. It expects the http.Response to contain a Location header providing the // URL at which to poll (using GET) and will poll until the time passed is equal to or greater than // the supplied duration. It will delay between requests for the duration specified in the // RetryAfter header or, if the header is absent, the passed delay. Polling may be canceled by // closing the optional channel on the http.Request. func DoPollForStatusCodes(duration time.Duration, delay time.Duration, codes ...int) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (resp *http.Response, err error) { resp, err = s.Do(r) if err == nil && ResponseHasStatusCode(resp, codes...) { r, err = NewPollingRequest(resp, r.Cancel) for err == nil && ResponseHasStatusCode(resp, codes...) { Respond(resp, ByDiscardingBody(), ByClosing()) resp, err = SendWithSender(s, r, AfterDelay(GetRetryAfter(resp, delay))) } } return resp, err }) } } // DoRetryForAttempts returns a SendDecorator that retries a failed request for up to the specified // number of attempts, exponentially backing off between requests using the supplied backoff // time.Duration (which may be zero). Retrying may be canceled by closing the optional channel on // the http.Request. func DoRetryForAttempts(attempts int, backoff time.Duration) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (resp *http.Response, err error) { rr := NewRetriableRequest(r) for attempt := 0; attempt < attempts; attempt++ { err = rr.Prepare() if err != nil { return resp, err } resp, err = s.Do(rr.Request()) if err == nil { return resp, err } DelayForBackoff(backoff, attempt, r.Cancel) } return resp, err }) } } // DoRetryForStatusCodes returns a SendDecorator that retries for specified statusCodes for up to the specified // number of attempts, exponentially backing off between requests using the supplied backoff // time.Duration (which may be zero). Retrying may be canceled by closing the optional channel on // the http.Request. func DoRetryForStatusCodes(attempts int, backoff time.Duration, codes ...int) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (resp *http.Response, err error) { rr := NewRetriableRequest(r) // Increment to add the first call (attempts denotes number of retries) attempts++ for attempt := 0; attempt < attempts; attempt++ { err = rr.Prepare() if err != nil { return resp, err } resp, err = s.Do(rr.Request()) if err != nil || !ResponseHasStatusCode(resp, codes...) { return resp, err } delayed := DelayWithRetryAfter(resp, r.Cancel) if !delayed { DelayForBackoff(backoff, attempt, r.Cancel) } } return resp, err }) } } // DelayWithRetryAfter invokes time.After for the duration specified in the "Retry-After" header in // responses with status code 429 func DelayWithRetryAfter(resp *http.Response, cancel <-chan struct{}) bool { retryAfter, _ := strconv.Atoi(resp.Header.Get("Retry-After")) if resp.StatusCode == http.StatusTooManyRequests && retryAfter > 0 { select { case <-time.After(time.Duration(retryAfter) * time.Second): return true case <-cancel: return false } } return false } // DoRetryForDuration returns a SendDecorator that retries the request until the total time is equal // to or greater than the specified duration, exponentially backing off between requests using the // supplied backoff time.Duration (which may be zero). Retrying may be canceled by closing the // optional channel on the http.Request. func DoRetryForDuration(d time.Duration, backoff time.Duration) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (resp *http.Response, err error) { rr := NewRetriableRequest(r) end := time.Now().Add(d) for attempt := 0; time.Now().Before(end); attempt++ { err = rr.Prepare() if err != nil { return resp, err } resp, err = s.Do(rr.Request()) if err == nil { return resp, err } DelayForBackoff(backoff, attempt, r.Cancel) } return resp, err }) } } // WithLogging returns a SendDecorator that implements simple before and after logging of the // request. func WithLogging(logger *log.Logger) SendDecorator { return func(s Sender) Sender { return SenderFunc(func(r *http.Request) (*http.Response, error) { logger.Printf("Sending %s %s", r.Method, r.URL) resp, err := s.Do(r) if err != nil { logger.Printf("%s %s received error '%v'", r.Method, r.URL, err) } else { logger.Printf("%s %s received %s", r.Method, r.URL, resp.Status) } return resp, err }) } } // DelayForBackoff invokes time.After for the supplied backoff duration raised to the power of // passed attempt (i.e., an exponential backoff delay). Backoff duration is in seconds and can set // to zero for no delay. The delay may be canceled by closing the passed channel. If terminated early, // returns false. // Note: Passing attempt 1 will result in doubling "backoff" duration. Treat this as a zero-based attempt // count. func DelayForBackoff(backoff time.Duration, attempt int, cancel <-chan struct{}) bool { select { case <-time.After(time.Duration(backoff.Seconds()*math.Pow(2, float64(attempt))) * time.Second): return true case <-cancel: return false } }