plugin_examples

README

Changes in v6.8.0

• Plugin commands can now have aliases
• Help text for plugins now listed in 'cf plugins'

Complete change log ...

Developing a Plugin

This README discusses how to develop a cf CLI plugin. For user-focused documentation, see Using the cf CLI.

Development Requirements

• Golang installed
• Tagged version of CLI release source code that supports plugins; cf CLI v.6.7.0 and above

Architecture Overview

The cf CLI plugin architecture model follows the remote procedure call (RPC) model. The cf CLI invokes each plugin, runs it as an independent executable, and handles all start, stop, and clean up tasks for plugin executable resources.

Here is an illustration of the workflow when a plugin command is being invoked.

1: CLI launches 2 processes, the rpc server and the independent plugin executable

2: Plugin establishes a connection to the RPC server, the connection is used to invoke core cli commands.

3: When a plugin invokes a cli command, it talks to the rpc server, and the rpc server interacts with cf cli to perform the command. The result is passed back to the plugin through the rpc server.

• Plugins that you develop for the cf CLI must conform to a predefined plugin interface that we discuss below.

Writing a Plugin

To write a plugin for the cf CLI, implement the predefined plugin interface.

The interface uses a Run(...) method as the main entry point between the CLI and a plugin. This method receives the following arguments:

• A struct plugin.CliConnection that contains methods for invoking cf CLI commands
• A string array that contains the arguments passed from the cf process

The GetMetadata() function informs the CLI of the name of a plugin, plugin version (optional), the commands it implements, and help text for each command that users can display with cf help.

To initialize a plugin, call plugin.Start(new(MyPluginStruct)) from within the main() method of your plugin. The plugin.Start(...) function requires a new reference to the struct that implements the defined interface.

This repo contains a basic plugin example here.
To see more examples, go here.

If you wish to employ TDD in your plugin development, here is an example of a plugin that calls core cli command with the use of FakeCliConnection for testing.

Using Command Line Arguments

The Run(...) method accepts the command line arguments and flags that you define for a plugin.

See the [command line arguments example] (https://github.com/cloudfoundry/cli/blob/master/plugin_examples/echo.go) included in this repo.

Calling CLI Commands

You can invoke CLI commands with cliConnection.CliCommand([]args) from within a plugin's Run(...) method. The Run(...) method receives the cliConnection as its first argument.

The cliConnection.CliCommand([]args) returns the output printed by the command and an error. The output is returned as a slice of strings. The error will be present if the call to the CLI command fails.

See the calling CLI commands example included in this repo.

Creating Interactive Plugins

Because a plugin has access to stdin during a call to the Run(...) method, you can create interactive plugins. See the interactive plugin example included in this repo.

Creating Plugins with multiple commands

A single plugin binary can have more than one command, and each command can have it's own help text defined. For an example of multi-comamnd plugins, see the multiple commands example

Compiling Plugin Source Code

The cf CLI requires an executable file to install the plugin. You must compile the source code with the go build command before distributing the plugin, or instruct your users to compile the plugin source code before installing the plugin. For information about compiling Go source code, see Compile packages and dependencies.

Using Plugins

After you compile a plugin, use the following commands to install and manage the plugin.

Installing Plugins

To install a plugin, run:

cf install-plugin PATH_TO_PLUGIN_BINARY

Listing Plugins

To display a list of installed plugins and the commands available from each plugin, run:

cf plugins

Uninstalling Plugins

To remove a plugin, run:

cf uninstall-plugin PLUGIN_NAME

Known Issues

• When invoking a CLI command using cliConnection.CliCommand([]args) a plugin developer will not receive output generated by the codegangsta/cli package. This includes usage failures when executing a cli command, cf help, or cli SOME-COMMAND -h.

Documentation

Overview

* * This is an example plugin where we use both arguments and flags. The plugin * will echo all arguments passed to it. The flag -uppercase will upcase the * arguments passed to the command. *