github.com/dcarley/cf-cli@v6.24.1-0.20170220111324-4225ff346898+incompatible/plugin/plugin_examples/README.md (about)

     1  If you have any questions about developing a CLI plugin, ask away on the [cf-dev mailing list](https://lists.cloudfoundry.org/archives/list/cf-dev@lists.cloudfoundry.org/) (many plugin developers there!) or the #cli channel in our Slack community.
     2  
     3  # Changes in v6.24.0
     4  - API `LoggregatorEndpoint()` is deprecated and now always returns the empty string. Use `DopplerEndpoint()` instead to obtain logs.
     5  
     6  # Changes in v6.17.0
     7  - `-v` is now a global flag to enable verbose logging of API calls, equivalent to `CF_TRACE=true`. This means that the `-v` flag will no longer be passed to plugins.
     8  
     9  # Changes in v6.14.0
    10  - API `AccessToken()` now provides a refreshed o-auth token.
    11  - [Examples](https://github.com/cloudfoundry/cli/tree/master/plugin/plugin_examples#test-driven-development-tdd) on how to use fake `CliConnection` and test RPC server for TDD development.
    12  - Fix Plugin API file descriptors leakage.
    13  - Fix bug where some CLI versions does not respect `PluginMetadata.MinCliVersion`.
    14  - The field `PackageUpdatedAt` returned by `GetApp()` API is now populated.
    15  
    16  [Complete change log ...](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/CHANGELOG.md)
    17  
    18  # Developing a Plugin
    19  [Go here for documentation of the plugin API](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/DOC.md)
    20  
    21  This README discusses how to develop a cf CLI plugin.
    22  For user-focused documentation, see [Using the cf CLI](http://docs.cloudfoundry.org/cf-cli/use-cli-plugins.html).
    23  
    24  *If you wish to share your plugin with the community, see [here](http://github.com/cloudfoundry-incubator/cli-plugin-repo) for plugin submission.
    25  
    26  
    27  ## Development Requirements
    28  
    29  - GoLang installed
    30  - Tagged version of CLI release source code that supports plugins; cf CLI v.6.7.0 and above
    31  
    32  ## Architecture Overview
    33  
    34  The cf CLI plugin architecture model follows the remote procedure call (RPC) model.
    35  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.
    36  
    37  Here is an illustration of the work flow when a plugin command is being invoked.
    38  
    39  1: CLI launches 2 processes, the rpc server and the independent plugin executable
    40  <p align="center">
    41  <img src="https://raw.githubusercontent.com/cloudfoundry/cli/master/plugin/plugin_examples/images/rpc_flow1.png" alt="workflow 1" width="400px">
    42  </p>
    43  
    44  2: Plugin establishes a connection to the RPC server, the connection is used to invoke core cli commands.
    45  <p align="center">
    46  <img src="https://raw.githubusercontent.com/cloudfoundry/cli/master/plugin/plugin_examples/images/rpc_flow2.png" alt="workflow 1" width="400px">
    47  </p>
    48  
    49  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.
    50  <p align="center">
    51  <img src="https://raw.githubusercontent.com/cloudfoundry/cli/master/plugin/plugin_examples/images/rpc_flow3.png" alt="workflow 1" width="400px">
    52  </p>
    53  
    54  - Plugins that you develop for the cf CLI must conform to a predefined plugin interface that we discuss below.
    55  
    56  ## Writing a Plugin
    57  
    58  [Go here for documentation of the plugin API](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/DOC.md)
    59  
    60  To write a plugin for the cf CLI, implement the [predefined plugin interface](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin.go).
    61  
    62  The interface uses a `Run(...)` method as the main entry point between the CLI and a plugin. This method receives the following arguments:
    63  
    64    - A struct `plugin.CliConnection` that contains methods for invoking cf CLI commands
    65    - A string array that contains the arguments passed from the `cf` process
    66  
    67  The `GetMetadata()` function informs the CLI of the name of a plugin, plugin version (optional), minimum Cli version required (optional), the commands it implements, and help text for each command that users can display with `cf help`.
    68  
    69    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.
    70  
    71  This repo contains a basic plugin example [here](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/basic_plugin.go).<br>
    72  To see more examples, go [here](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/).
    73  
    74  ### Uninstalling A Plugin
    75  Uninstall of the plugin needs to be explicitly handled. When a user calls the `cf uninstall-plugin` command, CLI notifies the plugin via a call with `CLI-MESSAGE-UNINSTALL` as the first item in `[]args` from within the plugin's `Run(...)` method.
    76  
    77  ### Test Driven Development (TDD)
    78  2 libraries are available for TDD
    79  - `FakeCliConnection`: stub/mock the `plugin.CliConnection` object with this fake [See example](https://github.com/cloudfoundry/cli/tree/master/plugin/plugin_examples/call_cli_cmd/main)
    80  - `Test RPC server`: a RPC server to be used as a back end for the plugin. Allows plugin to be tested as a stand along binary without replying on CLI as a back end. [See example](https://github.com/cloudfoundry/cli/tree/master/plugin/plugin_examples/test_rpc_server_example)
    81  
    82  ### Using Command Line Arguments
    83  
    84  The `Run(...)` method accepts the command line arguments and flags that you define for a plugin.
    85  
    86    See the [command line arguments example] (https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/echo.go) included in this repo.
    87  
    88  #### Global Flags
    89  There are several global flags that will not be passed to the plugin. These are:
    90  - `-v`: equivalent to `CF_TRACE=true`, will display any API calls/responses to the user
    91  - `-h`: will process the return from the plugin's `GetMetadata` function to produce a help display
    92  
    93  ### Calling CLI Commands
    94  
    95  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.
    96  
    97  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.
    98  
    99  See the [calling CLI commands example](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/call_cli_cmd/main/call_cli_cmd.go) included in this repo.
   100  
   101  ### Creating Interactive Plugins
   102  
   103  Because a plugin has access to stdin during a call to the `Run(...)` method, you can create interactive plugins. See the [interactive plugin example](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/interactive.go) included in this repo.
   104  
   105  ### Creating Plugins with multiple commands
   106  
   107  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-command plugins, see the [multiple commands example](https://github.com/cloudfoundry/cli/blob/master/plugin/plugin_examples/multiple_commands.go)
   108  
   109  ### Enforcing a minimum CLI version required for the plugin.
   110  
   111  ```go
   112  func (c *cmd) GetMetadata() plugin.PluginMetadata {
   113  	return plugin.PluginMetadata{
   114  		Name: "Test1",
   115  		MinCliVersion: plugin.VersionType{
   116  			Major: 6,
   117  			Minor: 12,
   118  			Build: 0,
   119  		},
   120  	}
   121  }
   122  ```
   123  
   124  ## Compiling Plugin Source Code
   125  
   126  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](https://golang.org/cmd/go/).
   127  
   128  ## Using Plugins
   129  
   130  After you compile a plugin, use the following commands to install and manage the plugin.
   131  
   132  ### Installing Plugins
   133  
   134  To install a plugin, run:
   135  
   136  `cf install-plugin PATH_TO_PLUGIN_BINARY`
   137  
   138  ### Listing Plugins
   139  
   140  To display a list of installed plugins and the commands available from each plugin, run:
   141  
   142  `cf plugins`
   143  
   144  ### Uninstalling Plugins
   145  
   146  To remove a plugin, run:
   147  
   148  `cf uninstall-plugin PLUGIN_NAME`
   149  
   150  ## Known Issues
   151  
   152  - When invoking a CLI command using `cliConnection.CliCommand([]args)` a plugin will not receive output generated by the cli package. This includes usage failures when executing a cli command, `cf help`, or `cli SOME-COMMAND -h`.
   153  - When invoking a CLI command using `cliConnection.CliCommand([]args)` and `CF_TRACE=true/cf -v` a plugin will receive all the output, including the trace in the returned string array. This may cause problem while trying to debug output with `CF_TRACE`. As work around, if a plugin is running `cf curl` via `CliCommand`, the following can be used to help with debugging (when the `CF_DEBUG_CURL=true`):
   154  ```go
   155    func RunCurl(cliConnection plugin.CliConnection, args []string) ([]string, error) {
   156      output, err := cliConnection.CliCommand("curl", args...)
   157      if os.Getenv("CF_DEBUG_CURL") == "true" {
   158        fmt.Println(strings.Join(output, "\n"))
   159      }
   160      return output, err
   161    }
   162  ```
   163  - Due to architectural limitations, calling CLI core commands is not concurrency-safe. The correct execution of concurrent commands is not guaranteed. An architecture restructuring is in the works to fix this in the near future.