auto detect hostname and ip

conf/config.toml

@@ -3,6 +3,11 @@
 print_configs = false
 
 # add label(agent_hostname) to series
+# "" -> auto detect hostname
+# "xx" -> use specified string xx
+# "$hostname" -> auto detect hostname
+# "$ip" -> auto detect ip
+# "$hostname-$ip" -> auto detect hostname and ip to replace the vars
 hostname = ""
 
 # will not add label(agent_hostname) if true

config/config.go

@@ -3,8 +3,10 @@ package config
 import (
 	"encoding/json"
 	"fmt"
+	"net"
 	"os"
 	"path"
+	"strings"
 	"time"
 
 	"flashcat.cloud/categraf/pkg/cfg"
@@ -72,12 +74,8 @@ func InitConfig(configDir string, debugMode bool, testMode bool) error {
 		return fmt.Errorf("failed to load configs of dir: %s", configDir)
 	}
 
-	if Config.Global.Hostname == "" {
-		name, err := os.Hostname()
-		if err != nil {
-			return fmt.Errorf("failed to get hostname: %v", err)
-		}
-		Config.Global.Hostname = name
+	if err := Config.fillHostname(); err != nil {
+		return err
 	}
 
 	if Config.Global.PrintConfigs {
@@ -88,6 +86,38 @@ func InitConfig(configDir string, debugMode bool, testMode bool) error {
 	return nil
 }
 
+func (c *ConfigType) fillHostname() error {
+	if c.Global.Hostname == "" {
+		name, err := GetHostname()
+		if err != nil {
+			return err
+		}
+
+		c.Global.Hostname = name
+		return nil
+	}
+
+	if strings.Contains(c.Global.Hostname, "$hostname") {
+		name, err := GetHostname()
+		if err != nil {
+			return err
+		}
+
+		c.Global.Hostname = strings.Replace(c.Global.Hostname, "$hostname", name, -1)
+	}
+
+	if strings.Contains(c.Global.Hostname, "$ip") {
+		ip, err := GetOutboundIP()
+		if err != nil {
+			return err
+		}
+
+		c.Global.Hostname = strings.Replace(c.Global.Hostname, "$ip", fmt.Sprint(ip), -1)
+	}
+
+	return nil
+}
+
 func GetInterval() time.Duration {
 	if Config.Global.Interval <= 0 {
 		return time.Second * 15
@@ -95,3 +125,20 @@ func GetInterval() time.Duration {
 
 	return time.Duration(Config.Global.Interval)
 }
+
+func GetHostname() (string, error) {
+	return os.Hostname()
+}
+
+// Get preferred outbound ip of this machine
+func GetOutboundIP() (net.IP, error) {
+	conn, err := net.Dial("udp", "8.8.8.8:80")
+	if err != nil {
+		return nil, fmt.Errorf("failed to get outbound ip: %v", err)
+	}
+	defer conn.Close()
+
+	localAddr := conn.LocalAddr().(*net.UDPAddr)
+
+	return localAddr.IP, nil
+}