mirror of
https://github.com/coredns/coredns.git
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128 lines
3.4 KiB
Go
128 lines
3.4 KiB
Go
package proxy
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// functions other plugin might want to use to do lookup in the same style as the proxy.
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import (
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"context"
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"fmt"
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"net"
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"sync/atomic"
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"time"
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"github.com/coredns/coredns/plugin/pkg/healthcheck"
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"github.com/coredns/coredns/request"
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"github.com/miekg/dns"
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)
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// NewLookup create a new proxy with the hosts in host and a Random policy.
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func NewLookup(hosts []string) Proxy { return NewLookupWithOption(hosts, Options{}) }
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// NewLookupWithOption process creates a simple round robin forward with potentially forced proto for upstream.
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func NewLookupWithOption(hosts []string, opts Options) Proxy {
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p := Proxy{Next: nil}
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// TODO(miek): this needs to be unified with upstream.go's NewStaticUpstreams, caddy uses NewHost
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// we should copy/make something similar.
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upstream := &staticUpstream{
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from: ".",
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HealthCheck: healthcheck.HealthCheck{
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FailTimeout: 5 * time.Second,
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MaxFails: 3,
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},
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ex: newDNSExWithOption(opts),
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}
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upstream.Hosts = make([]*healthcheck.UpstreamHost, len(hosts))
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for i, host := range hosts {
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uh := &healthcheck.UpstreamHost{
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Name: host,
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FailTimeout: upstream.FailTimeout,
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CheckDown: checkDownFunc(upstream),
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}
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upstream.Hosts[i] = uh
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}
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p.Upstreams = &[]Upstream{upstream}
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return p
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}
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// Lookup will use name and type to forge a new message and will send that upstream. It will
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// set any EDNS0 options correctly so that downstream will be able to process the reply.
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func (p Proxy) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
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req := new(dns.Msg)
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req.SetQuestion(name, typ)
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state.SizeAndDo(req)
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state2 := request.Request{W: state.W, Req: req}
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return p.lookup(state2)
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}
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// Forward forward the request in state as-is. Unlike Lookup that adds EDNS0 suffix to the message.
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func (p Proxy) Forward(state request.Request) (*dns.Msg, error) {
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return p.lookup(state)
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}
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func (p Proxy) lookup(state request.Request) (*dns.Msg, error) {
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upstream := p.match(state)
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if upstream == nil {
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return nil, errInvalidDomain
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}
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for {
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start := time.Now()
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reply := new(dns.Msg)
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var backendErr error
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// Since Select() should give us "up" hosts, keep retrying
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// hosts until timeout (or until we get a nil host).
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for time.Since(start) < tryDuration {
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host := upstream.Select()
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if host == nil {
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return nil, fmt.Errorf("%s: %s", errUnreachable, "no upstream host")
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}
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// duplicated from proxy.go, but with a twist, we don't write the
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// reply back to the client, we return it and there is no monitoring to update here.
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atomic.AddInt64(&host.Conns, 1)
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reply, backendErr = upstream.Exchanger().Exchange(context.TODO(), host.Name, state)
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atomic.AddInt64(&host.Conns, -1)
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if backendErr == nil {
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if !state.Match(reply) {
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return state.ErrorMessage(dns.RcodeFormatError), nil
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}
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return reply, nil
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}
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if oe, ok := backendErr.(*net.OpError); ok {
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if oe.Timeout() { // see proxy.go for docs.
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continue
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}
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}
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timeout := host.FailTimeout
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if timeout == 0 {
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timeout = defaultFailTimeout
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}
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atomic.AddInt32(&host.Fails, 1)
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fails := atomic.LoadInt32(&host.Fails)
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go func(host *healthcheck.UpstreamHost, timeout time.Duration) {
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time.Sleep(timeout)
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atomic.AddInt32(&host.Fails, -1)
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if fails%failureCheck == 0 { // Kick off healthcheck on eveyry third failure.
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host.HealthCheckURL()
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}
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}(host, timeout)
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}
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return nil, fmt.Errorf("%s: %s", errUnreachable, backendErr)
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}
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}
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