| package gensupport |
| |
| import ( |
| "io" |
| "net" |
| "net/http" |
| "time" |
| |
| "golang.org/x/net/context" |
| ) |
| |
| // Retry invokes the given function, retrying it multiple times if the connection failed or |
| // the HTTP status response indicates the request should be attempted again. ctx may be nil. |
| func Retry(ctx context.Context, f func() (*http.Response, error), backoff BackoffStrategy) (*http.Response, error) { |
| for { |
| resp, err := f() |
| |
| var status int |
| if resp != nil { |
| status = resp.StatusCode |
| } |
| |
| // Return if we shouldn't retry. |
| pause, retry := backoff.Pause() |
| if !shouldRetry(status, err) || !retry { |
| return resp, err |
| } |
| |
| // Ensure the response body is closed, if any. |
| if resp != nil && resp.Body != nil { |
| resp.Body.Close() |
| } |
| |
| // Pause, but still listen to ctx.Done if context is not nil. |
| var done <-chan struct{} |
| if ctx != nil { |
| done = ctx.Done() |
| } |
| select { |
| case <-done: |
| return nil, ctx.Err() |
| case <-time.After(pause): |
| } |
| } |
| } |
| |
| // DefaultBackoffStrategy returns a default strategy to use for retrying failed upload requests. |
| func DefaultBackoffStrategy() BackoffStrategy { |
| return &ExponentialBackoff{ |
| Base: 250 * time.Millisecond, |
| Max: 16 * time.Second, |
| } |
| } |
| |
| // shouldRetry returns true if the HTTP response / error indicates that the |
| // request should be attempted again. |
| func shouldRetry(status int, err error) bool { |
| // Retry for 5xx response codes. |
| if 500 <= status && status < 600 { |
| return true |
| } |
| |
| // Retry on statusTooManyRequests{ |
| if status == statusTooManyRequests { |
| return true |
| } |
| |
| // Retry on unexpected EOFs and temporary network errors. |
| if err == io.ErrUnexpectedEOF { |
| return true |
| } |
| if err, ok := err.(net.Error); ok { |
| return err.Temporary() |
| } |
| |
| return false |
| } |