App Builder

The App Builder project builds CLI applications from YAML definitions, encapsulating shell scripts, piped commands, kubectl invocations, and other operational tools into a single discoverable command.

Operations teams tend to rely on a large selection of shell scripts and ad-hoc commands in their day-to-day work. This tribal knowledge is a hurdle for new team members. Wiki-based run books that capture these commands do not scale well and do not stay up to date.

App Builder solves this by specifying a model for a CLI application in a YAML file and building custom interfaces on the fly. When the underlying commands change, only the app model needs updating - the CLI interface and any wiki pages that reference it remain stable.

A video introduction covers the motivation behind App Builder.

Example

The following example shows App Builder in use:

$ natsctl --help
usage: natsctl [<flags>] <command> [<args> ...]

NATS Stress Test Cluster Controller

Contact: R.I.Pienaar <rip@devco.net>

Flags:
  --help  Show context-sensitive help (also try --help-long and --help-man).

Commands:
  help [<command>...]
    Show help.

  report servers
    Shows list of NATS servers

  report jetstream
    Shows JetStream status

  service list [<flags>]
    List the servers running the service

  service state [<flags>]
    Obtain the state of the service operator
...

In the example above, commands like natsctl report servers or natsctl report jetstream invoke something like nats server list --user system --password secret --server nats.example.net:4222.

The natsctl service state command invokes a Choria RPC API in a subset of fleet nodes and passes the result through a JQ query .replies | .[] | select(.statuscode==0) | .sender + ": " + .data.state to transform the API output.

Wrapping these in natsctl report servers or natsctl service state keeps the detail managed separately. Wikis can reference natsctl report servers, and if the underlying command ever changes, only the app model needs updating.

All sub-commands include built-in help. Shell completion for bash and zsh is provided.