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