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fix: auto retry in exchangeWithoutCache

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This commit is contained in:
wwqgtxx 2022-11-19 08:51:00 +08:00
parent 16f8f77f5d
commit 23f286f24e
1 changed files with 21 additions and 4 deletions
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23
dns/resolver.go
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@ -187,12 +187,16 @@ func (r *Resolver) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, e
func (r *Resolver) exchangeWithoutCache(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) {
q := m.Question[0]
ch := r.group.DoChan(q.String(), func() (result any, err error) {
retryNum := 0
retryMax := 3
fn := func() (result any, err error) {
ctx, cancel := context.WithTimeout(context.Background(), resolver.DefaultDNSTimeout) // reset timeout in singleflight
defer cancel()
defer func() {
if err != nil {
result = retryNum
retryNum++
return
}
@ -210,7 +214,9 @@ func (r *Resolver) exchangeWithoutCache(ctx context.Context, m *D.Msg) (msg *D.M
return r.batchExchange(ctx, matched, m)
}
return r.batchExchange(ctx, r.main, m)
})
}
ch := r.group.DoChan(q.String(), fn)
var result singleflight.Result
@ -219,13 +225,24 @@ func (r *Resolver) exchangeWithoutCache(ctx context.Context, m *D.Msg) (msg *D.M
break
case <-ctx.Done():
select {
case result = <-ch:
case result = <-ch: // maybe ctxDone and chFinish in same time, get DoChan's result as much as possible
break
default:
go func() { // start a retrying monitor in background
result := <-ch
ret, err, shared := result.Val, result.Err, result.Shared
if err != nil && !shared && ret.(int) < retryMax { // retry
r.group.DoChan(q.String(), fn)
}
}()
return nil, ctx.Err()
}
}
ret, err, shared := result.Val, result.Err, result.Shared
if err != nil && !shared && ret.(int) < retryMax { // retry
r.group.DoChan(q.String(), fn)
}
if err == nil {
msg = ret.(*D.Msg)