Building a Rust HTTP Prober: Four Low-Level Lessons from Dropping reqwest for hyper

A developer building an uptime checker in Rust switched from the popular reqwest library to raw hyper after finding that reqwest's abstractions obscured the precise measurements a prober needs. Connection pooling was the first feature removed, since reusing warm TCP connections hides DNS, handshake, and TLS costs that a monitor is specifically designed to capture. The engineer also redesigned error handling so that failed connections still report whichever phases completed, allowing engineers to distinguish a hung TLS handshake from a dead DNS server. A custom error type carries per-phase timing even on failure, replacing reqwest's single flat error with structured diagnostic data. The author notes these patterns — fresh connections, phased timing, and error-embedded metrics — are broadly useful beyond uptime monitoring.