folgore-repro

Minimal code to attemp to reproduce coffee-tools/folgore#100 — folgore's esplora backend panics with ParseIntError { kind: InvalidDigit } when GET /blocks/tip/height returns a non-numeric body with HTTP 200.

Uses the same esplora-api crate and the same call chain as folgore (pre-fix):

client
    .raw_call("/blocks/tip/height")
    .map_err(|err| format!("{err}"))
    .map(|raw| raw_to_num(&raw))   // panics here on non-numeric body

Non-200 responses (429, 503, etc.) are caught by esplora-api's status check and never reach raw_to_num. The panic only triggers on a 200 OK with non-numeric content — e.g. an HTML error page served by a CDN or reverse proxy that preserves the 200 status.

Usage

# Default: 800 requests against blockstream.info/api
cargo run

# Custom URL and request count
cargo run -- "https://blockstream.info/api" 800
cargo run -- "https://blockstream.info/liquid/api" 800
cargo run -- "https://mempool.space/api" 800

# Hit rate limit threshold (700 req/hr on blockstream.info)
cargo run -- "https://blockstream.info/api" 750

If the bug is triggered, the process panics with:

thread 'main' panicked at 'impossible parse a string into a i64: ParseIntError { kind: InvalidDigit }'

If all requests succeed or return non-200 errors, it prints:

Done. No panic encountered.

Context

• Issue: coffee-tools/folgore#100
• Fix: coffee-tools/folgore#102
• First seen around Sep 23, 2025 in Core Lightning nodes using folgore as a bitcoin backend
• The fix converts raw_to_num to return Result instead of panicking, so the recovery strategy can retry
• Update: So far are unable to reproduce this issue