Module rate_limiter 

Simple in‑process rate limiter for tool execution.

This is a lightweight fallback used when the full governor crate is not available in the build. It limits the number of tool calls per second globally for the process. The limiter is deliberately cheap – a Mutex protecting a counter and a timestamp – because the surrounding code already performs async work, so contention is minimal.

The implementation is intentionally minimalistic: it provides a RateLimiter struct with a try_acquire() method that returns Ok(()) when the call is allowed or an Err when the limit would be exceeded. Callers can decide how to handle the error (e.g., retry after a delay or surface a user‑friendly message).

Usage example:

use vtcode_core::tools::rate_limiter::GLOBAL_RATE_LIMITER;

fn execute_tool() -> anyhow::Result<()> {
    GLOBAL_RATE_LIMITER.try_acquire()?;
    // … actual tool logic …
    Ok(())
}

The limiter is configured via environment variables to keep the core library free of additional runtime configuration files:

• VTTOOL_RATE_LIMIT – maximum calls per second (default = 20).
• VTTOOL_BURST – maximum burst size (default = rate limit, min 5).

The values are read once at startup.

This file is added as part of the optimization plan to provide a central rate‑limiting mechanism for all external tool invocations (PTY, web fetch, filesystem, etc.).

Structs

PerToolRateLimiter

Per-tool rate limiter for finer-grained control. Each tool gets its own token bucket, allowing different rate limits per tool.

RateLimiterConfig

Configuration for the limiter.

RateLimiterInner

Simple token‑bucket implementation.

Statics

GLOBAL_RATE_LIMITER

PER_TOOL_RATE_LIMITER

Global per-tool rate limiter instance.

Functions

try_acquire

Public API – try to acquire permission for a tool call.

try_acquire_for

Try to acquire permission for a specific tool. Uses per-tool rate limiting for finer-grained control.

Type Aliases

RateLimiter

Public alias for benchmark compatibility