Read TOXIPROXY_* environment variables if they exist as default value…

…s for the hostname

cli/cli.go

@@ -215,7 +215,7 @@ func main() {
 		&cli.StringFlag{
 			Name:        "host",
 			Aliases:     []string{"h"},
-			Value:       "http://localhost:8474",
+			Value:       defaultUrl(),
 			Usage:       "toxiproxy host to connect to",
 			Destination: &hostname,
 		},
@@ -614,6 +614,26 @@ func listToxics(toxics toxiproxy.Toxics, stream string) {
 	}
 }
 
+const fallbackUrl = "http://localhost:8474"
+
+func defaultUrl() string {
+	// For our purposes an unset variable is treated the same as a variable set
+	// to an empty string
+	url, _ := os.LookupEnv("TOXIPROXY_URL")
+	if url != "" {
+		return url
+	}
+
+	host, _ := os.LookupEnv("TOXIPROXY_HOST")
+	port, _ := os.LookupEnv("TOXIPROXY_PORT")
+
+	if host != "" && port != "" {
+		return fmt.Sprintf("http://%s:%s", strings.TrimPrefix(host, "http://"), port)
+	}
+
+	return fallbackUrl
+}
+
 func getArgOrFail(c *cli.Context, name string) (string, error) {
 	arg := c.String(name)
 	if arg == "" {