Node.fz
This repository contains a modified version of the popular Node.js JavaScript runtime framework, version 0.12.7. The modifications are exclusively (I think) to the libuv subsystem, which fundamentally provides Node.js's event-driven nature. Their purpose is to increase the non-determinism already inherent in Node.js's asynchronous, event-driven nature. The goal of increasing the non-determinism is to flush out race conditions in the Node.js application being executed.
The changes I made to Node.js are detailed in the associated paper. Essentially, I probabilistically re-order the event queue, constrained by legal or practical ordering guarantees prescribed by the Node.js and libuv documentation.
Does it work?
As described in the associated paper, Node.fz can:
- reproduce race conditions more effectively than Node.js
- increase the schedule space explored by a test suite
Node.fz will make a great addition to your testing methodology, continuous integration pipelines, etc. Once you've worked out obvious bugs in your program, replace the installation of Node.js with Node.fz, and then re-run your test suite to look for race conditions.
The fuzzing benchmark applications used in the paper are available here. See the README within it for details. Warning: the tarball is (quite unnecessarily) 200MB and expands to 800MB.
How do I use it?
Follow the standard Node.js compilation procedure, as described elsewhere in this repository.
Then replace the version of Node.js installed on your machine with the resulting binary (e.g. with make install).
Node.fz's behavior can be controlled using the following environment variables:
| Parameter | Recommended value |
|---|---|
| UV_THREADPOOL_SIZE* | 1 |
| UV_SCHEDULER_TYPE* | "TP_FREEDOM" |
| UV_SCHEDULER_MODE* | "RECORD" |
| UV_SILENT* | "1" |
| UV_SCHEDULER_TP_DEG_FREEDOM | 5 |
| UV_SCHEDULER_TP_MAX_DELAY | 100 |
| UV_SCHEDULER_TP_EPOLL_THRESHOLD | 100 |
| UV_SCHEDULER_TIMER_LATE_EXEC_TPERC | 250 |
| UV_SCHEDULER_IOPOLL_DEG_FREEDOM | -1 |
| UV_SCHEDULER_IOPOLL_DEFER_PERC | 10 |
| UV_SCHEDULER_RUN_CLOSING_DEFER_PERC | 5 |
*Feel free to tune all but these parameters.
See deps/uv/src/uv-common.c for an in-depth explanation of each parameter.
Limitations
Node.fz is a dynamic test tool. It is only as good as the test suite being used to drive it. If there's a bug in function B but your test suite never calls this function, obviously Node.fz won't help you.
Contributing
The initial prototype of Node.fz was implemented by James (Jamie) Davis.
Please reach out to me to discuss any pull requests you'd like to submit. The most needed change is porting it up to a more recent version of Node.js (libuv). I think this should be pretty straightforward.
Citing this work
If you use this work, please give credit to the associated paper, e.g.
Davis, James, Arun Thekumparampil, and Dongyoon Lee. "Node. fz: Fuzzing the Server-Side Event-Driven Architecture." Proceedings of the Twelfth European Conference on Computer Systems. ACM, 2017.