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plugin/cache: configure stale TTL and failure recheck (#8411)

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* plugin/cache: configure stale response TTL

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>

* plugin/cache: delay stale refresh retries

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>

* plugin/cache: validate stale refresh responses

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>

---------

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>
This commit is contained in:
houyuwushang
2026-08-14 14:27:42 +08:00
committed by GitHub
parent 6199dc50a5
commit 9520d725d6
8 changed files with 757 additions and 72 deletions
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38
plugin/cache/item.go vendored
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@@ -28,13 +28,12 @@ type item struct {
*freq.Freq
// refreshing is set via CAS when a prefetch goroutine is dispatched for
// this item and cleared when it returns, bounding in-flight prefetches
// per item to one. A successful prefetch replaces this item in the cache
// with a new one (zero-valued refreshing); the deferred clear matters
// only when the prefetch fails and this item remains cached, so the next
// hit can retry.
// refreshing bounds in-flight refreshes for this item to one. retryAfter
// suppresses another attempt after a failed refresh when failure recheck
// is configured. A successful refresh normally replaces this item with a
// new one whose refresh state is zero-valued.
refreshing atomic.Bool
retryAfter atomic.Pointer[time.Time]
}
func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
@@ -79,6 +78,12 @@ func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
// On newer systems(e.g. ubuntu 16.04 with glib version 2.23), this issue is resolved.
// So we may set this bit back to 0 in the future ?
func (i *item) toMsg(m *dns.Msg, now time.Time, do bool, ad bool) *dns.Msg {
ttl := uint32(i.ttl(now)) // #nosec G115 -- ttl is bounded by DNS TTL limits
return i.toMsgWithTTL(m, ttl, do, ad)
}
// toMsgWithTTL returns the cached item with an explicit TTL on every RR.
func (i *item) toMsgWithTTL(m *dns.Msg, ttl uint32, do bool, ad bool) *dns.Msg {
m1 := new(dns.Msg)
m1.SetReply(m)
@@ -95,7 +100,6 @@ func (i *item) toMsg(m *dns.Msg, now time.Time, do bool, ad bool) *dns.Msg {
m1.RecursionAvailable = i.RecursionAvailable
m1.Rcode = i.Rcode
ttl := uint32(i.ttl(now)) // #nosec G115 -- ttl is bounded by DNS TTL limits
m1.Answer = filterRRSlice(i.Answer, ttl, true)
m1.Ns = filterRRSlice(i.Ns, ttl, true)
m1.Extra = filterRRSlice(i.Extra, ttl, true)
@@ -114,3 +118,23 @@ func (i *item) matches(state request.Request) bool {
}
return false
}
func (i *item) beginRefresh(now time.Time, failureRecheck time.Duration) bool {
if failureRecheck > 0 {
if retryAfter := i.retryAfter.Load(); retryAfter != nil && now.Before(*retryAfter) {
return false
}
}
return i.refreshing.CompareAndSwap(false, true)
}
func (i *item) endRefresh(now time.Time, failureRecheck time.Duration, refreshed bool) {
if failureRecheck > 0 && !refreshed {
retryAfter := now.Add(failureRecheck)
i.retryAfter.Store(&retryAfter)
} else {
i.retryAfter.Store(nil)
}
// Publish the retry deadline before allowing another refresh to start.
i.refreshing.Store(false)
}