Repository demonstrating that Node.js has a GC race condition, and that setting --max-old-space-size to a lower figure to force GC at an earlier point doesn't help.
We write a program that allocates memory as quickly as it can, while only maintaining references to the most recently allocated 150MB, and then run the program within a Docker container with a hard limit of 250MB. This approximates the environment of a Node.js server that's working through memory heavy requests as quickly as it can.
- The program crashes because it exceeds the container's hard limit (
250MB), and we can be sure of this because it doesn't crash at all if no memory limit is imposed.- It instead starts consuming vast amounts of swap memory but continues running.
- The program crashes at a different point each time it's run, showing that it's a race condition.
- Explicitly setting
--max-old-space-sizeto a lower figure (200MB) so that GC is forced to be taken more seriously at an earlier point doesn't prevent the server from crashing, or produce noticeably better results.