#parallel #concurrent #lock #macro #testing

macro nonparallel

Rust macro for ensuring non-parallel execution of functions

1 unstable release

0.1.0 Oct 9, 2019

#851 in Procedural macros




CircleCI License

A procedural macro for Rust that allows you to ensure that functions are not running at the same time. This is especially useful for integration tests, where tests that are writing to the same database table should not run in parallel.

The goal of mutual exclusion is achieved by acquiring a mutex at the beginning of the annotated function. So in essence this macro is syntactical sugar for writing MUT.lock().unwrap() at the beginning of every function.

Different functions can synchronize on different mutexes. That's why a static mutex reference must be passed to the nonparallel annotation.


use std::sync::Mutex;
use lazy_static::lazy_static;
use nonparallel::nonparallel;

// Create two locks
lazy_static! { static ref MUT_A: Mutex<()> = Mutex::new(()); }
lazy_static! { static ref MUT_B: Mutex<()> = Mutex::new(()); }

// Mutually exclude parallel runs of functions using those two locks

fn function_a1() {
    // This will not run in parallel to function_a2

fn function_a2() {
    // This will not run in parallel to function_a1

fn function_b() {
    // This may run in parallel to function_a*


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