func baseRetryPolicy()

in client.go [472:514]
26 lines of code
11 McCabe index (conditional complexity)

func baseRetryPolicy(resp *http.Response, err error) (bool, error) {
	if err != nil {
		if v, ok := err.(*url.Error); ok {
			// Don't retry if the error was due to too many redirects.
			if redirectsErrorRe.MatchString(v.Error()) {
				return false, v
			}

			// Don't retry if the error was due to an invalid protocol scheme.
			if schemeErrorRe.MatchString(v.Error()) {
				return false, v
			}

			// Don't retry if the error was due to TLS cert verification failure.
			if notTrustedErrorRe.MatchString(v.Error()) {
				return false, v
			}
			if _, ok := v.Err.(x509.UnknownAuthorityError); ok {
				return false, v
			}
		}

		// The error is likely recoverable so retry.
		return true, nil
	}

	// 429 Too Many Requests is recoverable. Sometimes the server puts
	// a Retry-After response header to indicate when the server is
	// available to start processing request from client.
	if resp.StatusCode == http.StatusTooManyRequests {
		return true, nil
	}

	// Check the response code. We retry on 500-range responses to allow
	// the server time to recover, as 500's are typically not permanent
	// errors and may relate to outages on the server side. This will catch
	// invalid response codes as well, like 0 and 999.
	if resp.StatusCode == 0 || (resp.StatusCode >= 500 && resp.StatusCode != http.StatusNotImplemented) {
		return true, fmt.Errorf("unexpected HTTP status %s", resp.Status)
	}

	return false, nil
}