How to Fix a SharedArrayBuffer Data Race Between Web Workers

Your web game splits simulation across workers sharing a SharedArrayBuffer, and the numbers occasionally come out wrong or jitter. Plain typed-array writes are not atomic and race across workers. Here is how to synchronize them.

How to fix it

1. Use Atomics for shared cells

Replace view[i] = x and view[i] on shared indices with Atomics.store(view, i, x) and Atomics.load(view, i) so each access is atomic and ordered.

2. Use atomic add for counters

For shared counters use Atomics.add(view, i, 1) instead of read-modify-write, which would lose concurrent increments.

3. Coordinate with wait and notify

Use Atomics.wait in the consumer and Atomics.notify in the producer to hand off work without busy-spinning, and remember the cross-origin isolation headers SharedArrayBuffer requires.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every HTML5 error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.