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Designing a Human-Friendly CLI for API-Driven Infrastructure

north hall
30 minutes


As Bloomberg’s infrastructure grows and evolves, the tools we use to manage it are becoming increasingly important. To streamline infrastructure management, our team set out to design a REST API and constituent CLI (Command Line Interface) that would comprise a single interface for both programmatic and human interaction with our infrastructure. Traditionally, building a CLI that is tightly coupled to an API requires maintaining a separate codebase, which is tedious and error-prone. Instead, we designed a CLI that dynamically generates commands based on the OpenAPI JSON documentation. However, since APIs are designed for computer interaction, we designed our API to include the information needed to implement a human-friendly CLI. Leveraging Python, FastAPI, and numerous other open source projects, we built a stable, extensible tool that greatly improves how we interact with our infrastructure.

TalkInfrastructure: Cloud & Hardware


In this talk, we will share our experience designing a resilient infrastructure API with a human-friendly CLI that does not need continued development, even as the API evolves.

We will discuss some of the specific approaches we used to build a dynamically-updated CLI with human-friendly features:

  • Extending OpenAPI to communicate CLI intent
  • Using templating languages (Jinja) to convert the API’s response JSON into human readable output
  • Defining CLI command aliases to abstract long, verbose API endpoints
  • Embedding CLI help text in the API to generate well-documented commands
  • Other small enhancements and strategies that improve the CLI user’s quality-of-life.

Furthermore, we will also discuss how we leveraged several open source projects and standards to accomplish our goals, including Python, FastAPI, OpenAPI, Jinja, OAuth2, Pydantic, prompt_toolkit, and more.

The speaker

Oliver Rew

As a software engineer and a lifelong tinkerer/maker, I have a deep-rooted passion for building, fixing, and breaking things. I recently earned a Masters in Electrical and Computer Engineering, and have gained experience working at both small startups and large companies. I thrive on fixing hard bugs and diving deep into challenging problems.

Beyond my professional work, I'm also involved in an exciting Cubesat project at Portland State University. When I'm not immersed in technology, I enjoy outdoor activities such as biking, rock-climbing, and spending quality time with my dog, Bruce.

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