Adding a Plugin

To add a plugin, create a new .go file in the traffic_ops_ort/atstccfg/plugin directory. This file should have a unique name, to avoid conflicts. Consider prefixing it with your company name, website, or a UUID.

The filename, sans .go, is the name of your plugin, and will be the key used for configuration in the remap file. For example, if your file is f49e54fc-fd17-4e1c-92c6-67028fde8504-hello-world.go, the name of your plugin is f49e54fc-fd17-4e1c-92c6-67028fde8504-hello-world.

Plugins are registered via calls to AddPlugin inside an init function in the plugin's file. The AddPlugin function takes a priority, and a set of hook functions. The priority is the order in which plugins are called, starting from 0. Note the priority of plugins included with Traffic Control use a base priority of 10000, unless priority order matters for them.

The Funcs object contains functions for each hook. The current hooks are startup and onRequest. If your plugin does not use a hook, it may be nil.

• startup is called when the application starts.

• onRequest is called immediately when a request is received. It returns a boolean indicating whether to stop processing.

The simplest example is the hello_world plugin. See plugin/hello_world.go.

import (
	"strings"
)
func init() {
	AddPlugin(10000, Funcs{onRequest: hello})
}
const HelloPath = "/_hello_world"
func hello(d OnRequestData) IsRequestHandled {
	if d.Cfg.TOURL.Path != HelloPath {
		return RequestUnhandled
	}
	cfgFile := "Hello World!\n"
	fmt.Println(cfgFile)
	os.Exit(42)
	return RequestHandled
}

The plugin is initialized via AddPlugin, and its hello function is set as the onRequest hook. The hello function has the signature of plugin.OnRequestFunc.

Examples

Example plugins are included in the /plugin directory

hello_world: Example of a simple HTTP endpoint.

Glossary

Definitions of terms used in this document.

Plugin: A self-contained component whose code is executed when certain events in the main application occur. Hook: A plugin function which is called when a certain event happens in the main application. Plugin Data: Application data given to a plugin, as a function parameter passed to a hook function, including configuration data, running state, and HTTP request state.