a20b4fe2de
- each proxy stores average RTT (round trip time) of last rttCount queries. For now, I assigned the value 4 to rttCount - the read timeout is calculated as doubled average RTT, but it cannot exceed default timeout - initial avg RTT is set to a half of default timeout, so initial timeout is equal to default timeout - the RTT for failed read is considered equal to default timeout, so any failed read will lead to increasing average RTT (up to default timeout) - dynamic timeouts will let us react faster on lost UDP packets - in future, we may develop a low-latency forward policy based on collected RTT values of proxies
95 lines
2.2 KiB
Go
95 lines
2.2 KiB
Go
package forward
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import (
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"crypto/tls"
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"sync/atomic"
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"time"
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"github.com/coredns/coredns/plugin/pkg/up"
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"github.com/miekg/dns"
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)
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// Proxy defines an upstream host.
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type Proxy struct {
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addr string
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client *dns.Client
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// Connection caching
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expire time.Duration
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transport *transport
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// health checking
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probe *up.Probe
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fails uint32
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avgRtt int64
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}
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// NewProxy returns a new proxy.
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func NewProxy(addr string, tlsConfig *tls.Config) *Proxy {
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p := &Proxy{
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addr: addr,
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fails: 0,
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probe: up.New(),
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transport: newTransport(addr, tlsConfig),
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avgRtt: int64(timeout / 2),
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}
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p.client = dnsClient(tlsConfig)
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return p
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}
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// dnsClient returns a client used for health checking.
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func dnsClient(tlsConfig *tls.Config) *dns.Client {
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c := new(dns.Client)
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c.Net = "udp"
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// TODO(miek): this should be half of hcDuration?
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c.ReadTimeout = 1 * time.Second
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c.WriteTimeout = 1 * time.Second
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if tlsConfig != nil {
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c.Net = "tcp-tls"
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c.TLSConfig = tlsConfig
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}
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return c
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}
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// SetTLSConfig sets the TLS config in the lower p.transport.
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func (p *Proxy) SetTLSConfig(cfg *tls.Config) { p.transport.SetTLSConfig(cfg) }
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// SetExpire sets the expire duration in the lower p.transport.
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func (p *Proxy) SetExpire(expire time.Duration) { p.transport.SetExpire(expire) }
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// Dial connects to the host in p with the configured transport.
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func (p *Proxy) Dial(proto string) (*dns.Conn, bool, error) { return p.transport.Dial(proto) }
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// Yield returns the connection to the pool.
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func (p *Proxy) Yield(c *dns.Conn) { p.transport.Yield(c) }
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// Healthcheck kicks of a round of health checks for this proxy.
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func (p *Proxy) Healthcheck() { p.probe.Do(p.Check) }
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// Down returns true if this proxy is down, i.e. has *more* fails than maxfails.
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func (p *Proxy) Down(maxfails uint32) bool {
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if maxfails == 0 {
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return false
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}
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fails := atomic.LoadUint32(&p.fails)
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return fails > maxfails
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}
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// close stops the health checking goroutine.
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func (p *Proxy) close() {
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p.probe.Stop()
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p.transport.Stop()
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}
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// start starts the proxy's healthchecking.
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func (p *Proxy) start(duration time.Duration) { p.probe.Start(duration) }
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const (
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dialTimeout = 4 * time.Second
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timeout = 2 * time.Second
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hcDuration = 500 * time.Millisecond
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)
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