hotpath_init

Initialize hotpath Profiling

Set up hotpath profiling in the current Rust project. The setup is fully feature-gated: zero compile-time and runtime overhead unless the hotpath feature is explicitly enabled. All macros are noops when the feature is off, so no cfg_attr wrapping is needed.

Steps

1. Inspect the project

• Find the binary crate(s) and the main function. If there is no main you control (e.g. a library or a test harness), use the HotpathGuardBuilder API instead of #[hotpath::main] (see step 3).
• Detect the async runtime (tokio, smol, none) and which instrumentable primitives the code uses: channels (tokio::sync::mpsc/oneshot, std::sync::mpsc, crossbeam_channel, flume, async-channel, futures_channel), Mutex and RwLock (std/parking_lot/tokio/async-lock), futures streams, sqlx, diesel, reqwest clients (async only; note which reqwest major - 0.12 or 0.13), axum 0.8 routers (find where the Router is finished and passed to axum::serve), byte-level I/O values implementing std::io::Read/Write or tokio::io::AsyncRead/AsyncWrite (files, sockets, compression codecs).

2. Add the dependency and feature passthrough

In the target crate's Cargo.toml:

[dependencies]
hotpath = "0.25"

[features]
hotpath = ["hotpath/hotpath"]
hotpath-alloc = ["hotpath/hotpath-alloc"]
hotpath-prometheus = ["hotpath/hotpath-prometheus"]

Enable extra hotpath cargo features on the dependency based on what the project uses:

• tokio - for tokio::sync channel instrumentation, async io! traits (AsyncRead/AsyncWrite), and hotpath::tokio_runtime!() metrics: hotpath = { version = "0.25", features = ["tokio"] }
• crossbeam - for crossbeam_channel instrumentation
• futures - for futures_channel instrumentation
• flume - for flume channel instrumentation
• async-channel - for async-channel instrumentation
• parking_lot - for parking_lot RwLock/Mutex instrumentation
• async-lock - for async-lock RwLock/Mutex instrumentation
• sqlx - for SQL query profiling via hotpath::sqlx_tracing_layer()
• diesel - for SQL query profiling via hotpath::instrument_diesel_sql()
• reqwest-0-12 / reqwest-0-13 - for HTTP request profiling via hotpath::http!(client); pick the feature matching the project's reqwest major version
• axum-0-8 - for server-side response time profiling per axum 0.8 route via hotpath::axum!(router)