e54c232c8c
Make the cache memory bounded, by using a LRU cache. Also split the
cache in a positive and negative one - each with its own controls.
Extend the cache stanza to allow for this:
cache {
positive limit [ttl]
negative limit [ttl]
}
is now possible. This also add a cache_test.go in the toplevel test/
directory that exercises the caching path.
Fixes #260
78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
package cache
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import (
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"time"
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"github.com/miekg/coredns/middleware"
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"github.com/miekg/coredns/request"
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"github.com/miekg/dns"
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"github.com/prometheus/client_golang/prometheus"
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"golang.org/x/net/context"
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)
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// ServeDNS implements the middleware.Handler interface.
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func (c *Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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state := request.Request{W: w, Req: r}
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qname := state.Name()
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qtype := state.QType()
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zone := middleware.Zones(c.Zones).Matches(qname)
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if zone == "" {
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return c.Next.ServeDNS(ctx, w, r)
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}
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do := state.Do() // might need more from OPT record? Like the actual bufsize?
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if i, ok, expired := c.get(qname, qtype, do); ok && !expired {
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resp := i.toMsg(r)
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state.SizeAndDo(resp)
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w.WriteMsg(resp)
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cacheHitCount.WithLabelValues(zone).Inc()
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return dns.RcodeSuccess, nil
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}
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cacheMissCount.WithLabelValues(zone).Inc()
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crr := &ResponseWriter{w, c}
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return c.Next.ServeDNS(ctx, crr, r)
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}
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func (c *Cache) get(qname string, qtype uint16, do bool) (*item, bool, bool) {
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k := rawKey(qname, qtype, do)
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if i, ok := c.ncache.Get(k); ok {
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return i.(*item), ok, i.(*item).expired(time.Now())
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}
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if i, ok := c.pcache.Get(k); ok {
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return i.(*item), ok, i.(*item).expired(time.Now())
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}
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return nil, false, false
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}
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var (
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cacheHitCount = prometheus.NewCounterVec(prometheus.CounterOpts{
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Namespace: middleware.Namespace,
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Subsystem: subsystem,
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Name: "hit_count_total",
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Help: "Counter of DNS requests that were found in the cache.",
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}, []string{"zone"})
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cacheMissCount = prometheus.NewCounterVec(prometheus.CounterOpts{
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Namespace: middleware.Namespace,
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Subsystem: subsystem,
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Name: "miss_count_total",
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Help: "Counter of DNS requests that were not found in the cache.",
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}, []string{"zone"})
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)
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const subsystem = "cache"
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func init() {
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prometheus.MustRegister(cacheHitCount)
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prometheus.MustRegister(cacheMissCount)
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}
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