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package proxy
// functions other middleware might want to use to do lookup in the same style as the proxy.
import (
"context"
"sync/atomic"
"time"
"github.com/coredns/coredns/request"
"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{})
}
// NewLookupWithForcedProto process creates a simple round robin forward with potentially forced proto for upstream.
func NewLookupWithOption(hosts []string, opts Options) Proxy {
p := Proxy{Next: nil}
upstream := &staticUpstream{
from: ".",
Hosts: make([]*UpstreamHost, len(hosts)),
Policy: &Random{},
Spray: nil,
FailTimeout: 10 * time.Second,
MaxFails: 3, // TODO(miek): disable error checking for simple lookups?
ex: newDNSExWithOption(opts),
}
for i, host := range hosts {
uh := &UpstreamHost{
Name: host,
Conns: 0,
Fails: 0,
FailTimeout: upstream.FailTimeout,
Unhealthy: false,
CheckDown: func(upstream *staticUpstream) UpstreamHostDownFunc {
return func(uh *UpstreamHost) bool {
if uh.Unhealthy {
return true
}
fails := atomic.LoadInt32(&uh.Fails)
if fails >= upstream.MaxFails && upstream.MaxFails != 0 {
return true
}
return false
}
}(upstream),
WithoutPathPrefix: upstream.WithoutPathPrefix,
}
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()
// Since Select() should give us "up" hosts, keep retrying
// hosts until timeout (or until we get a nil host).
for time.Now().Sub(start) < tryDuration {
host := upstream.Select()
if host == nil {
return nil, errUnreachable
}
// 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.
atomic.AddInt64(&host.Conns, 1)
reply, backendErr := upstream.Exchanger().Exchange(context.TODO(), host.Name, state)
atomic.AddInt64(&host.Conns, -1)
if backendErr == nil {
return reply, nil
}
timeout := host.FailTimeout
if timeout == 0 {
timeout = 10 * time.Second
}
atomic.AddInt32(&host.Fails, 1)
go func(host *UpstreamHost, timeout time.Duration) {
time.Sleep(timeout)
atomic.AddInt32(&host.Fails, -1)
}(host, timeout)
}
return nil, errUnreachable
}
}
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