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package srslog
import (
"io"
"net"
"time"
)
// netConn has an internal net.Conn and adheres to the serverConn interface,
// allowing us to send syslog messages over the network.
type netConn struct {
conn net.Conn
done chan interface{}
}
// newNetConn creates a netConn instance that is monitored for unexpected socket closure.
func newNetConn(conn net.Conn) *netConn {
nc := &netConn{conn: conn, done: make(chan interface{})}
go monitor(nc.conn, nc.done)
return nc
}
// writeString formats syslog messages using time.RFC3339 and includes the
// hostname, and sends the message to the connection.
func (n *netConn) writeString(framer Framer, formatter Formatter, p Priority, hostname, tag, msg string) error {
if framer == nil {
framer = DefaultFramer
}
if formatter == nil {
formatter = DefaultFormatter
}
formattedMessage := framer(formatter(p, hostname, tag, msg))
_, err := n.conn.Write([]byte(formattedMessage))
return err
}
// close the network connection
func (n *netConn) close() error {
// signal monitor goroutine to exit
close(n.done)
// wake up monitor blocked on read (close usually is enough)
_ = n.conn.SetReadDeadline(time.Now())
// close the connection
return n.conn.Close()
}
// monitor continuously tries to read from the connection to detect socket close.
// This is needed because syslog server uses a write only socket and Linux systems
// take a long time to detect a loss of connectivity on a socket when only writing;
// the writes simply fail without an error returned.
func monitor(conn net.Conn, done chan interface{}) {
defer Logger.Println("monitor exit")
buf := make([]byte, 1)
for {
Logger.Println("monitor loop")
select {
case <-done:
return
case <-time.After(1 * time.Second):
}
err := conn.SetReadDeadline(time.Now().Add(time.Second * 30))
if err != nil {
continue
}
_, err = conn.Read(buf)
Logger.Println("monitor -- ", err)
if err == io.EOF {
Logger.Println("monitor close conn")
conn.Close()
}
}
}
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