34ffb2b314
Changes large parts of proxy lookup mechanism. The duplicate zone checking erroneous added a nameserver for each zone we are auth. for, creating to many backend hosts. So even when a host was determined do be Down() we still got an (identical) new one from the list. The Down() and failure checking for upstream hosts had data race in the uh.Fails check - we now use atomic.LoadInt32 for that. Use and debug the test/server.go test servers implementation in the TestStubLookup test to prevent going out to the internet. Also delete the stub cycle test. That test was wrong and did not test what it needed to be testing. Deleted for now.
121 lines
3.4 KiB
Go
121 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.
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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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type Client struct {
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UDP *dns.Client
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TCP *dns.Client
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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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return dns.RcodeServerFailure, errUnreachable
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}
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reverseproxy := ReverseProxy{Host: host.Name, Client: p.Client, Options: upstream.Options()}
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atomic.AddInt64(&host.Conns, 1)
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backendErr := reverseproxy.ServeDNS(w, r, nil)
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atomic.AddInt64(&host.Conns, -1)
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if backendErr == nil {
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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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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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func Clients() Client {
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udp := newClient("udp", defaultTimeout)
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tcp := newClient("tcp", defaultTimeout)
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return Client{UDP: udp, TCP: tcp}
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}
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// newClient returns a new client for proxy requests.
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func newClient(net string, timeout time.Duration) *dns.Client {
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if timeout == 0 {
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timeout = defaultTimeout
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}
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return &dns.Client{Net: net, ReadTimeout: timeout, WriteTimeout: timeout, SingleInflight: true}
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}
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const defaultTimeout = 5 * time.Second
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