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// Package forward implements a forwarding proxy. It caches an upstream net.Conn for some time, so if the same
// client returns the upstream's Conn will be precached. Depending on how you benchmark this looks to be
// 50% faster than just openening a new connection for every client. It works with UDP and TCP and uses
// inband healthchecking.
package forward
import (
"io"
"strconv"
"time"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
func (p *Proxy) connect(ctx context.Context, state request.Request, forceTCP, metric bool) (*dns.Msg, error) {
start := time.Now()
proto := state.Proto()
if forceTCP {
proto = "tcp"
}
conn, cached, err := p.Dial(proto)
if err != nil {
return nil, err
}
// Set buffer size correctly for this client.
conn.UDPSize = uint16(state.Size())
if conn.UDPSize < 512 {
conn.UDPSize = 512
}
conn.SetWriteDeadline(time.Now().Add(timeout))
if err := conn.WriteMsg(state.Req); err != nil {
conn.Close() // not giving it back
if err == io.EOF && cached {
return nil, errCachedClosed
}
return nil, err
}
conn.SetReadDeadline(time.Now().Add(timeout))
ret, err := conn.ReadMsg()
if err != nil {
conn.Close() // not giving it back
if err == io.EOF && cached {
return nil, errCachedClosed
}
return nil, err
}
p.Yield(conn)
if metric {
rc, ok := dns.RcodeToString[ret.Rcode]
if !ok {
rc = strconv.Itoa(ret.Rcode)
}
RequestCount.WithLabelValues(p.addr).Add(1)
RcodeCount.WithLabelValues(rc, p.addr).Add(1)
RequestDuration.WithLabelValues(p.addr).Observe(time.Since(start).Seconds())
}
return ret, nil
}
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