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Why I Started Building a Network Introspection Tool in Rust

#rust #opensource #networking #systems

Why I Started Building a Network Introspection Tool in Rust

Modern software development has become increasingly distributed. Even when working locally, a single request often travels through multiple services, databases, caches, and APIs before returning a response.

A simple login request might look something like this:

Client
   │
   ▼
HTTP API
   │
   ▼
Authentication Service
   │
   ├── PostgreSQL
   ├── Redis
   └── External OAuth Provider
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When something goes wrong, developers usually reach for logs.

Then more logs.

Then database queries.

Then packet captures.

Then another terminal.

Eventually, you're trying to reconstruct what happened by mentally stitching together information from half a dozen tools.

I kept asking myself:

Why isn't there a tool that simply shows the journey of a request?

That question became the starting point for Lens.

The Problem

Current debugging tools each solve part of the problem.

Logs tell you what your application thinks happened.

Database logs tell you what the database received.

Packet analyzers show network traffic.

Distributed tracing platforms provide excellent visibility—but they often require instrumentation, configuration, and infrastructure that aren't practical for local development.

For many projects, especially during early development, I wanted something much simpler.

Run a tool.

Start the application.

Watch requests flow through the system.

What I Wanted

The goal wasn't another packet analyzer.

It wasn't another tracing platform.

It wasn't another dashboard.

I wanted a developer tool that answered simple questions instantly:

  • Which service handled this request?
  • Which database queries were executed?
  • Was Redis involved?
  • Where did latency occur?
  • What did the complete request path look like?

Ideally, all inside a terminal.

Why Rust?

This project touches several areas where Rust is particularly well suited.

  • High-performance networking
  • Asynchronous I/O
  • Protocol parsing
  • Cross-platform support
  • Memory safety

Tokio provides an excellent asynchronous runtime, while Rust's ownership model makes it easier to build networking software without worrying about memory corruption or data races.

Performance also matters.

A debugging tool should add as little overhead as possible.

Designing Lens

Rather than requiring changes to application code, Lens is being built around a transparent proxy architecture.

The idea is to sit between applications and the services they communicate with.

That allows Lens to observe traffic, decode supported protocols, redact sensitive information, and present request flows in real time.

Current areas of development include:

  • HTTP/1.1 support
  • PostgreSQL protocol decoding
  • Secret redaction
  • Interactive terminal UI
  • Modular Cargo workspace
  • Cross-platform support

The architecture is intentionally modular so additional protocols can be added without affecting the core runtime.

Lessons So Far

Even before completing the implementation, a few things have become clear.

Invest in architecture early.

It's much easier to reorganize diagrams than thousands of lines of code.

Write documentation while decisions are fresh.

Architecture Decision Records (ADRs) have already prevented me from revisiting the same design questions multiple times.

Contributor experience matters.

If an open-source project hopes to attract contributors, documentation, issue organization, and onboarding shouldn't be afterthoughts.

What's Next?

The immediate focus is implementing the remaining runtime and protocol components.

I'm especially interested in expanding protocol support while keeping the architecture clean and extensible.

If you've worked on networking tools, protocol parsers, or asynchronous systems in Rust, I'd genuinely appreciate feedback on the design.

The project is open source:

GitHub: https://github.com/dpsyfk/lens

Feedback, ideas, and discussions are always welcome.

Closing Thoughts

One of my goals with this series is to document the engineering decisions behind building Lens—from protocol parsing and async architecture to terminal UI design and contributor experience.

If you're interested in Rust systems programming, networking, or developer tooling, I hope you'll find the upcoming articles useful, whether or not you ever use Lens.

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