cd5879f866
Cache would let the first response through and would then cap subsequent ones to whatever the cache duration was. This would lead to huge drops in TTL values: 3600 -> 20 for instance, which is not only bad, but can mess up your careful TTL planning business. This PR fixes that and applies the cache duration to all replies. As a bonus I could remove a time.Sleep() from the cache test and just check for the cache duration as the TTL on the reply. Fixes #1038
119 lines
3.1 KiB
Go
119 lines
3.1 KiB
Go
package cache
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import (
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"time"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/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 plugin.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 := plugin.Zones(c.Zones).Matches(qname)
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if zone == "" {
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return plugin.NextOrFailure(c.Name(), c.Next, ctx, w, r)
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}
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do := state.Do() // TODO(): might need more from OPT record? Like the actual bufsize?
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now := time.Now().UTC()
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i, ttl := c.get(now, qname, qtype, do)
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if i != nil && ttl > 0 {
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resp := i.toMsg(r)
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state.SizeAndDo(resp)
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resp, _ = state.Scrub(resp)
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w.WriteMsg(resp)
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i.Freq.Update(c.duration, now)
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pct := 100
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if i.origTTL != 0 { // you'll never know
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pct = int(float64(ttl) / float64(i.origTTL) * 100)
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}
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if c.prefetch > 0 && i.Freq.Hits() > c.prefetch && pct < c.percentage {
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// When prefetching we loose the item i, and with it the frequency
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// that we've gathered sofar. See we copy the frequencies info back
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// into the new item that was stored in the cache.
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prr := &ResponseWriter{ResponseWriter: w, Cache: c, prefetch: true}
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plugin.NextOrFailure(c.Name(), c.Next, ctx, prr, r)
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if i1, _ := c.get(now, qname, qtype, do); i1 != nil {
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i1.Freq.Reset(now, i.Freq.Hits())
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}
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}
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return dns.RcodeSuccess, nil
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}
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crr := &ResponseWriter{ResponseWriter: w, Cache: c}
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return plugin.NextOrFailure(c.Name(), c.Next, ctx, crr, r)
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}
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// Name implements the Handler interface.
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func (c *Cache) Name() string { return "cache" }
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func (c *Cache) get(now time.Time, qname string, qtype uint16, do bool) (*item, int) {
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k := hash(qname, qtype, do)
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if i, ok := c.ncache.Get(k); ok {
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cacheHits.WithLabelValues(Denial).Inc()
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return i.(*item), i.(*item).ttl(now)
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}
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if i, ok := c.pcache.Get(k); ok {
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cacheHits.WithLabelValues(Success).Inc()
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return i.(*item), i.(*item).ttl(now)
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}
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cacheMisses.Inc()
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return nil, 0
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}
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var (
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cacheSize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: plugin.Namespace,
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Subsystem: subsystem,
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Name: "size",
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Help: "The number of elements in the cache.",
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}, []string{"type"})
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cacheCapacity = prometheus.NewGaugeVec(prometheus.GaugeOpts{
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Namespace: plugin.Namespace,
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Subsystem: subsystem,
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Name: "capacity",
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Help: "The cache's capacity.",
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}, []string{"type"})
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cacheHits = prometheus.NewCounterVec(prometheus.CounterOpts{
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Namespace: plugin.Namespace,
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Subsystem: subsystem,
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Name: "hits_total",
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Help: "The count of cache hits.",
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}, []string{"type"})
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cacheMisses = prometheus.NewCounter(prometheus.CounterOpts{
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Namespace: plugin.Namespace,
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Subsystem: subsystem,
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Name: "misses_total",
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Help: "The count of cache misses.",
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})
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)
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const subsystem = "cache"
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func init() {
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prometheus.MustRegister(cacheSize)
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prometheus.MustRegister(cacheCapacity)
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prometheus.MustRegister(cacheHits)
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prometheus.MustRegister(cacheMisses)
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}
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