Initial client library for statsd backend.

Restricted to supporting just gauges now as counters or timing are not very useful for cAdvisor.

storage/statsd/client.go

@@ -0,0 +1,73 @@
+// Copyright 2015 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package statsd
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/golang/glog"
+)
+
+type Client struct {
+	HostPort string
+	conn     net.Conn
+}
+
+func (self *Client) Open() error {
+	conn, err := net.Dial("udp", self.HostPort)
+	if err != nil {
+		glog.Errorf("failed to open udp connection to %q: %v", self.HostPort, err)
+		return err
+	}
+	self.conn = conn
+	return nil
+}
+
+func (self *Client) Close() {
+	self.conn.Close()
+}
+
+func (self *Client) UpdateGauge(name, value string) error {
+	stats := make(map[string]string)
+	val := fmt.Sprintf("%s|g", value)
+	stats[name] = val
+	if err := self.send(stats); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Simple send to statsd daemon without sampling.
+func (self *Client) send(data map[string]string) error {
+	for k, v := range data {
+		formatted := fmt.Sprintf("%s:%s", k, v)
+		_, err := fmt.Fprintf(self.conn, formatted)
+		if err != nil {
+			glog.V(3).Infof("failed to send data %q: %v", formatted, err)
+			// return on first error.
+			return err
+		}
+	}
+	return nil
+}
+
+func New(hostPort string) (*Client, error) {
+	client := Client{HostPort: hostPort}
+	if err := client.Open(); err != nil {
+		return nil, err
+	}
+	return &client, nil
+}