drain.go

package udp

import (
	"fmt"
	"net"
	"net/url"
	"sync"
)

const maxConnUses = 100

type logDrain struct {
	uri      string
	conn     *net.Conn
	useCount int
	mutex    sync.RWMutex
}

// NewDrain returns a pointer to a new instance of a UDP-based drain.LogDrain.
func NewDrain(drainURL string) (*logDrain, error) {
	u, err := url.Parse(drainURL)
	if err != nil {
		return nil, err
	}
	if u.Scheme != "udp" && u.Scheme != "syslog" {
		return nil, fmt.Errorf("Invalid drain url scheme: %s", u.Scheme)
	}
	return &logDrain{uri: u.Host + u.Path}, nil
}

// Send forwards the provided log message to an external destination using UDP for transport.
func (d *logDrain) Send(message string) error {
	d.mutex.Lock()
	defer d.mutex.Unlock()
	if d.useCount == maxConnUses {
		(*d.conn).Close()
		d.conn = nil
		d.useCount = 0
	}
	if d.conn == nil {
		conn, err := net.Dial("udp", d.uri)
		if err != nil {
			return fmt.Errorf("Error dialing log drain at %s over udp: %s", d.uri, err)
		}
		d.conn = &conn
	}
	fmt.Fprintln(*d.conn, message)
	d.useCount++
	return nil
}