chore: add warning for unified delay test when second failed

adapter/adapter.go

@@ -10,6 +10,7 @@ import (
  "net/netip"
  "net/url"
  "strconv"
+ "strings"
  "time"
 
  "github.com/metacubex/mihomo/common/atomic"
@@ -18,6 +19,7 @@ import (
  "github.com/metacubex/mihomo/component/ca"
  "github.com/metacubex/mihomo/component/dialer"
  C "github.com/metacubex/mihomo/constant"
+ "github.com/metacubex/mihomo/log"
  "github.com/puzpuzpuz/xsync/v3"
 )
 
@@ -260,10 +262,18 @@ func (p *Proxy) URLTest(ctx context.Context, url string, expectedStatus utils.In
 
  if unifiedDelay {
  second := time.Now()
- resp, err = client.Do(req)
- if err == nil {
+ var ignoredErr error
+ var secondResp *http.Response
+ secondResp, ignoredErr = client.Do(req)
+ if ignoredErr == nil {
+ resp = secondResp
  _ = resp.Body.Close()
  start = second
+ } else {
+ if strings.HasPrefix(url, "http://") {
+ log.Errorln("%s failed to get the second response from %s: %v", p.Name(), url, ignoredErr)
+ log.Warnln("It is recommended to use HTTPS for provider.health-check.url and group.url to ensure better reliability. Due to some proxy providers hijacking test addresses and not being compatible with repeated HEAD requests, using HTTP may result in failed tests.")
+ }
  }
  }