f91cb61086
With Go 1.9 you *can* include the std lib's context package and nothing breaks. However we never officially made the move (and grpc also doesn't ues the std lib's one). Standardize all plugins on using the extern context package. Fixes #1466
122 lines
3.3 KiB
Go
122 lines
3.3 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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"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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"golang.org/x/net/context"
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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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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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