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plugin/cache: prefetch without holding a client connection (#7944)

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This commit is contained in:
rpb-ant
2026-03-24 11:47:11 -04:00
committed by GitHub
parent f582a01dc9
commit 31e16025ef
2 changed files with 67 additions and 31 deletions
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18
plugin/cache/handler.go vendored
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@@ -55,13 +55,13 @@ func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
// Adjust the time to get a 0 TTL in the reply built from a stale item.
now = now.Add(time.Duration(ttl) * time.Second)
if !c.verifyStale {
cw := newPrefetchResponseWriter(server, state, c)
go c.doPrefetch(ctx, state, cw, i, now)
cw := newPrefetchResponseWriter(server, rc, do, cd, c)
go c.doPrefetch(ctx, cw, i, now)
}
servedStale.WithLabelValues(server, c.zonesMetricLabel, c.viewMetricLabel).Inc()
} else if c.shouldPrefetch(i, now) {
cw := newPrefetchResponseWriter(server, state, c)
go c.doPrefetch(ctx, state, cw, i, now)
cw := newPrefetchResponseWriter(server, rc, do, cd, c)
go c.doPrefetch(ctx, cw, i, now)
}
if i.wildcard != "" {
@@ -91,16 +91,16 @@ func wildcardFunc(ctx context.Context) func() string {
}
}
func (c *Cache) doPrefetch(ctx context.Context, state request.Request, cw *ResponseWriter, i *item, now time.Time) {
func (c *Cache) doPrefetch(ctx context.Context, cw *ResponseWriter, i *item, now time.Time) {
// Use a fresh metadata map to avoid concurrent writes to the original request's metadata.
ctx = metadata.ContextWithMetadata(ctx)
cachePrefetches.WithLabelValues(cw.server, c.zonesMetricLabel, c.viewMetricLabel).Inc()
c.doRefresh(ctx, state, cw)
c.doRefresh(ctx, cw.state, cw)
// When prefetching we loose the item i, and with it the frequency
// that we've gathered sofar. See we copy the frequencies info back
// into the new item that was stored in the cache.
if i1 := c.exists(state); i1 != nil {
if i1 := c.exists(cw.state.Name(), cw.state.QType(), cw.do, cw.cd); i1 != nil {
i1.Reset(now, i.Hits())
}
}
@@ -145,8 +145,8 @@ func (c *Cache) getIfNotStale(now time.Time, state request.Request, server strin
}
// exists unconditionally returns an item if it exists in the cache.
func (c *Cache) exists(state request.Request) *item {
k := hash(state.Name(), state.QType(), state.Do(), state.Req.CheckingDisabled)
func (c *Cache) exists(name string, qtype uint16, do, cd bool) *item {
k := hash(name, qtype, do, cd)
if i, ok := c.ncache.Get(k); ok {
return i
}