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54964653d1
Add a separate request duration metrics specially for proxying requests upstream. Fixes #259
119 lines
3.4 KiB
Go
119 lines
3.4 KiB
Go
// Package proxy is middleware that proxies requests.
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package proxy
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import (
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"errors"
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"sync/atomic"
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"time"
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"github.com/miekg/coredns/middleware"
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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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var errUnreachable = errors.New("unreachable backend")
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// Proxy represents a middleware instance that can proxy requests to another DNS server.
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type Proxy struct {
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Next middleware.Handler
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Client *client
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Upstreams []Upstream
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}
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// Upstream manages a pool of proxy upstream hosts. Select should return a
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// suitable upstream host, or nil if no such hosts are available.
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type Upstream interface {
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// The domain name this upstream host should be routed on.
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From() string
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// Selects an upstream host to be routed to.
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Select() *UpstreamHost
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// Checks if subpdomain is not an ignored.
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IsAllowedPath(string) bool
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// Options returns the options set for this upstream
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Options() Options
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}
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// UpstreamHostDownFunc can be used to customize how Down behaves.
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type UpstreamHostDownFunc func(*UpstreamHost) bool
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// UpstreamHost represents a single proxy upstream
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type UpstreamHost struct {
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Conns int64 // must be first field to be 64-bit aligned on 32-bit systems
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Name string // IP address (and port) of this upstream host
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Fails int32
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FailTimeout time.Duration
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Unhealthy bool
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CheckDown UpstreamHostDownFunc
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WithoutPathPrefix string
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}
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// Down checks whether the upstream host is down or not.
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// Down will try to use uh.CheckDown first, and will fall
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// back to some default criteria if necessary.
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func (uh *UpstreamHost) Down() bool {
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if uh.CheckDown == nil {
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// Default settings
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fails := atomic.LoadInt32(&uh.Fails)
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return uh.Unhealthy || fails > 0
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}
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return uh.CheckDown(uh)
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}
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// tryDuration is how long to try upstream hosts; failures result in
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// immediate retries until this duration ends or we get a nil host.
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var tryDuration = 60 * time.Second
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// ServeDNS satisfies the middleware.Handler interface.
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func (p Proxy) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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for _, upstream := range p.Upstreams {
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start := time.Now()
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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.Now().Sub(start) < tryDuration {
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host := upstream.Select()
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if host == nil {
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RequestDuration.WithLabelValues(upstream.From()).Observe(float64(time.Since(start) / time.Millisecond))
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return dns.RcodeServerFailure, errUnreachable
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}
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atomic.AddInt64(&host.Conns, 1)
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reply, backendErr := p.Client.ServeDNS(w, r, host)
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atomic.AddInt64(&host.Conns, -1)
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if backendErr == nil {
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w.WriteMsg(reply)
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RequestDuration.WithLabelValues(upstream.From()).Observe(float64(time.Since(start) / time.Millisecond))
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return 0, nil
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}
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timeout := host.FailTimeout
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if timeout == 0 {
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timeout = 10 * time.Second
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}
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atomic.AddInt32(&host.Fails, 1)
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go func(host *UpstreamHost, timeout time.Duration) {
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time.Sleep(timeout)
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atomic.AddInt32(&host.Fails, -1)
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}(host, timeout)
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}
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RequestDuration.WithLabelValues(upstream.From()).Observe(float64(time.Since(start) / time.Millisecond))
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return dns.RcodeServerFailure, errUnreachable
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}
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return p.Next.ServeDNS(ctx, w, r)
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}
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// Name implements the Handler interface.
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func (p Proxy) Name() string { return "proxy" }
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// defaultTimeout is the default networking timeout for DNS requests.
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const defaultTimeout = 5 * time.Second
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