Module dst 

Deterministic simulation testing (DST) re-export module.

Feature-switched re-exports of the tokio primitives that need deterministic behavior under simulation: time, task, runtime, and signal. Code on the DST path imports async primitives from here rather than directly from tokio, so that toggling the simulation feature switches the whole runtime in one place.

Feature-switched behavior

The switch requires both the simulation Cargo feature (which enables the madsim dependency) and RUSTFLAGS="--cfg madsim" (which activates the simulation re-exports). Without both, all paths route to real tokio.

Only four submodules switch: time, task, runtime, and signal. All other tokio modules (sync, io, select!, fs, net) use real tokio unconditionally. Transitive crates (tokio-tungstenite, reqwest, …) are unaffected.

Surface

The submodules re-export the following items. A compile-time probe at the bottom of this file keeps the list and the signatures of the non-generic free functions consistent across the tokio and madsim routes, and fires on cargo build (not only cargo test) so breakage surfaces upstream.

• time: Duration, Instant, Interval, MissedTickBehavior, Sleep, error (submodule), interval, interval_at, sleep, sleep_until, timeout
• task: JoinHandle, spawn, spawn_local, yield_now
• runtime: Builder, Handle, Runtime
• signal: ctrl_c

Related seam

Monotonic time (Instant) goes through this module. Wall-clock time (SystemTime / Unix epoch) is a separate seam: see nautilus_core::time::duration_since_unix_epoch. Collapsing the two would lose epoch information and break order and fill timestamps.

Modules

runtime

Deterministic runtime: single-threaded sim runtime under simulation.

signal

Deterministic signal handling: injectable signals under simulation.

task

Deterministic task spawning: fixed-order scheduler under simulation.

time

Deterministic time: virtual time under simulation, real time in production.