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https://github.com/coredns/coredns.git
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dd9fc8962c
* Improve plugin/cache metrics * Add coredns_cache_prefetch_total metric to track number of prefetches. * Remove unnecessary Cache.get() call which would incorrectly increment cache counters. * Initialize all counters and gauges at zero. * Allow prefetching of a single request per ttl The original implementation didn't allow prefetching queries which are only requested once during the duration of a TTL. The minimum amount of queries which had to be seen was therefore capped at 2. This change also implements a real prefetch test. The existing test was a noop and always passed regardless of any prefetch implementation. * Fix prefetching for items with a short TTL The default prefetch threshold (percentage) is 10% of the lifetime of a cache item. With the previous implementation, this disabled prefetching for all items with a TTL < 10s (the resulting percentage would be 0, at which point a cached item is already discarded). This change uses a time based threshold calculation and ensures that a prefetch is triggered at a TTL of 1 at the latest. * Fix wrong duration reporting of cached responses The logging and metrics plugins (among others) included the duration of a cache prefetch in the request latency of client request. This change fixes this wrong reporting and executes the prefetch request in a goroutine in the background.
113 lines
2.5 KiB
Go
113 lines
2.5 KiB
Go
package cache
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import (
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"time"
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"github.com/coredns/coredns/plugin/cache/freq"
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"github.com/coredns/coredns/plugin/pkg/response"
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"github.com/miekg/dns"
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)
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type item struct {
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Rcode int
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Authoritative bool
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AuthenticatedData bool
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RecursionAvailable bool
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Answer []dns.RR
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Ns []dns.RR
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Extra []dns.RR
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origTTL uint32
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stored time.Time
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*freq.Freq
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}
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func newItem(m *dns.Msg, now time.Time, d time.Duration) *item {
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i := new(item)
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i.Rcode = m.Rcode
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i.Authoritative = m.Authoritative
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i.AuthenticatedData = m.AuthenticatedData
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i.RecursionAvailable = m.RecursionAvailable
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i.Answer = m.Answer
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i.Ns = m.Ns
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i.Extra = make([]dns.RR, len(m.Extra))
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// Don't copy OPT record as these are hop-by-hop.
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j := 0
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for _, e := range m.Extra {
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if e.Header().Rrtype == dns.TypeOPT {
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continue
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}
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i.Extra[j] = e
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j++
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}
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i.Extra = i.Extra[:j]
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i.origTTL = uint32(d.Seconds())
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i.stored = now.UTC()
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i.Freq = new(freq.Freq)
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return i
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}
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// toMsg turns i into a message, it tailors the reply to m.
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// The Authoritative bit is always set to 0, because the answer is from the cache.
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func (i *item) toMsg(m *dns.Msg, now time.Time) *dns.Msg {
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m1 := new(dns.Msg)
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m1.SetReply(m)
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m1.Authoritative = false
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m1.AuthenticatedData = i.AuthenticatedData
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m1.RecursionAvailable = i.RecursionAvailable
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m1.Rcode = i.Rcode
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m1.Compress = true
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m1.Answer = make([]dns.RR, len(i.Answer))
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m1.Ns = make([]dns.RR, len(i.Ns))
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m1.Extra = make([]dns.RR, len(i.Extra))
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ttl := uint32(i.ttl(now))
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for j, r := range i.Answer {
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m1.Answer[j] = dns.Copy(r)
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m1.Answer[j].Header().Ttl = ttl
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}
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for j, r := range i.Ns {
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m1.Ns[j] = dns.Copy(r)
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m1.Ns[j].Header().Ttl = ttl
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}
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for j, r := range i.Extra {
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m1.Extra[j] = dns.Copy(r)
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if m1.Extra[j].Header().Rrtype != dns.TypeOPT {
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m1.Extra[j].Header().Ttl = ttl
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}
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}
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return m1
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}
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func (i *item) ttl(now time.Time) int {
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ttl := int(i.origTTL) - int(now.UTC().Sub(i.stored).Seconds())
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return ttl
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}
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func minMsgTTL(m *dns.Msg, mt response.Type) time.Duration {
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if mt != response.NoError && mt != response.NameError && mt != response.NoData {
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return 0
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}
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minTTL := maxTTL
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for _, r := range append(m.Answer, m.Ns...) {
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switch mt {
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case response.NameError, response.NoData:
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if r.Header().Rrtype == dns.TypeSOA {
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return time.Duration(r.(*dns.SOA).Minttl) * time.Second
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}
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case response.NoError, response.Delegation:
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if r.Header().Ttl < uint32(minTTL.Seconds()) {
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minTTL = time.Duration(r.Header().Ttl) * time.Second
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}
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}
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}
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return minTTL
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}
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