func (c *StdClient) revalidate(
u *url.URL, r *http.Response, body []byte, cc *cache.Control,
) (
rr *http.Response, rcc *cache.Control, modified bool, err error,
) {
modified = true
req, _ := http.NewRequest("GET", u.String(), nil)
if cc.ETag != "" {
req.Header.Add("If-None-Match", cc.ETag)
}
var t time.Time
if t = cc.LastModified; t.IsZero() {
t = cc.Date
}
req.Header.Add("If-Modified-Since", t.Format(http.TimeFormat))
if rr, err = c.client.Do(req); err != nil {
return
}
switch {
case rr.StatusCode == 304:
rr.Body.Close()
rr = cache.Construct(r, rr, body)
if rr.Request.URL.String() == u.String() {
modified = false
}
fallthrough
case 200 <= rr.StatusCode && rr.StatusCode < 300:
rcc = cache.Parse(rr, time.Now())
if rcc == nil || !rcc.IsCacheable() {
c.cache.Remove(u)
}
return
// 5xx and 4xx but 404 are retryable.
case rr.StatusCode >= 500:
fallthrough
case rr.StatusCode >= 400 && rr.StatusCode != 404:
rr.Body.Close()
err = RetryableError{
Err: ResponseStatusError(rr.StatusCode),
}
return
default:
rr.Body.Close()
err = ResponseStatusError(rr.StatusCode)
return
}
}
// Do implements the Client interface.
func (c *StdClient) Do(req *Request) (r *Response, err error) {
defer func() {
if err != nil && r != nil {
r.free()
}
}()
var (
hr *http.Response
cc *cache.Control
body []byte
now time.Time
ok bool
modified bool = true
)
if req.Method == "GET" && c.cache != nil {
if hr, body, cc, ok = c.cache.Get(req.URL); ok {
if cc.NeedValidate() {
if hr, cc, modified, err = c.revalidate(
req.URL, hr, body, cc,
); err != nil {
return
}
} else {
modified = false
hr.Body = ioutil.NopCloser(bytes.NewReader(body))
}
now = time.Now()
goto INIT
}
}
if hr, err = c.client.Do(req.Request); err != nil {
return nil, RetryableError{Err: err}
}
now = time.Now()
// Only status code 2xx is OK.
switch {
case 200 <= hr.StatusCode && hr.StatusCode < 300:
// 5xx and 4xx but 404 are retryable.
case hr.StatusCode >= 500:
fallthrough
case hr.StatusCode >= 400 && hr.StatusCode != 404:
hr.Body.Close()
err = RetryableError{
Err: ResponseStatusError(hr.StatusCode),
}
return
default:
hr.Body.Close()
err = ResponseStatusError(hr.StatusCode)
return
}
if c.cache != nil {
cc = cache.Parse(hr, now)
}
INIT:
r = NewResponse()
r.init(req.URL, hr, now, cc)
if c.cache != nil && cc != nil && cc.IsCacheable() {
if !modified { // Just update cached header
if ok := c.cache.Update(req.URL, r.CacheControl, r.Header); ok {
return
}
}
r.Body = c.cache.NewReader(r.NewURL, r.CacheControl, r.Response, r.Body)
}
return
}