npm-accel 0.1

Accelerator for npm, the Node.js package manager

The npm-accel program is a wrapper for npm (the Node.js package manager) that optimizes one specific use case: Building a node_modules directory from a package.json file as quickly as possible. It works on the assumption that you build node_modules directories more frequently then you change the contents of package.json files, because it computes a fingerprint of the dependencies and uses that fingerprint as a cache key, to cache the complete node_modules directory in a tar archive. The npm-accel project is currently tested on Python 2.6, 2.7, 3.4, 3.5 and PyPy (yes, it’s written in Python, deal with it :-P).

• Status

• Performance

• Installation

• Usage

• Future improvements

• Contact

• License

Status

The npm-accel project was developed and published in September ‘16 because I got fed up waiting for npm install to finish, specifically in the context of continuous integration builds and deployments (where you frequently start with an empty node_modules directory). It was developed in about a week without much prior knowledge about Node.js or npm, which explains why it’s written in Python :-P. On the one hand npm-accel hasn’t seen much actual use, on the other hand it has a test suite with about 95% test coverage and I was careful not to repeat the bugs I encountered in npm-cache and npm-fast-install while evaluating those tools :-).

To summarize: Give it a try, see if it actually speeds up your npm install commands and then decide whether you want to use it or not.

Performance

The following table lists the output of npm-accel --benchmark (with some enhancements) against a private code base with about 30 dependencies listed in the package.json file (resulting in a 401 MB node_modules directory):

Approach	Iteration	Elapsed time	Percentage
npm install	1/2	1 minute and 36 seconds	100.0%
npm install	2/2	1 minute and 40 seconds	104.1%
npm-accel	1/2	1 minute and 40 seconds	104.1%
npm-accel	2/2	7.26 seconds	7.5%
npm-cache install npm	1/2	3 minutes and 9 seconds	196.8%
npm-cache install npm	2/2	2 minutes and 9 seconds	134.3%
npm-fast-install	1/2	1 minute and 5 seconds	72.2%
npm-fast-install	2/2	1 minute and 6 seconds	73.3%

Installation

The npm-accel package is available on PyPI which means installation should be as simple as:

$ pip install npm-accel

There’s actually a multitude of ways to install Python packages (e.g. the per user site-packages directory, virtual environments or just installing system wide) and I have no intention of getting into that discussion here, so if this intimidates you then read up on your options before returning to these instructions ;-).

Usage

There are two ways to use the npm-accel package: As the command line program npm-accel and as a Python API. For details about the Python API please refer to the API documentation available on Read the Docs. The command line interface is described below.

Usage: npm-accel [OPTIONS] [DIRECTORY]

The npm-accel program is a wrapper for npm (the Node.js package manager) that optimizes one specific use case: Building a “node_modules” directory from a “package.json” file as quickly as possible.

It works on the assumption that you build “node_modules” directories more frequently then you change the contents of “package.json” files, because it computes a fingerprint of the dependencies and uses that fingerprint as a cache key, to cache the complete “node_modules” directory in a tar archive.

Supported options:

Option	Description
-p, --production	Don’t install modules listed in “devDependencies”.
-i, --installer=NAME	Set the installer to use. Supported values for NAME are “npm” (the default), “npm-cache” and “npm-fast-install”.
-c, --cache-directory=DIR	Set the pathname of the directory where the npm-accel cache is stored.
-n, --no-cache	Disallow writing to the cache managed by npm-accel (reading is still allowed though). This option doesn’t disable the caching that’s done by npm-cache and npm-fast-install internally.
-b, --benchmark	Benchmark and compare the following installation methods: npm install npm-accel npm-cache npm-fast-install The first method performs no caching (except for the HTTP caching that’s native to npm) while the other three methods each manage their own cache (that is to say, the caching logic of npm-accel will only be used in the second method). Warning: Benchmarking wipes the caches managed by npm, npm-accel, npm-cache and npm-fast-install in order to provide a fair comparison (you can override this in the Python API but not on the command line).
-r, --remote-host=SSH_ALIAS	Operate on a remote system instead of the local system. The SSH_ALIAS argument gives the SSH alias of the remote host.
-v, --verbose	Make more noise.
-q, --quiet	Make less noise.
-h, --help	Show this message and exit.

Future improvements

Automatic cache invalidation

Currently the ~/.cache/npm-accel directory will simply keep growing as new installations are added to the cache. Eventually I want npm-accel to automatically remove cache entries that are no longer being used. Given that “last accessed time” of files is frequently disabled in high performance situations like continuous integration environments and build servers I may need to enhance the cache directory with metadata per cache entry. I’m still thinking about the best way to approach this…

Accelerate installations with changes

Currently when the fingerprint (cache key) of the dependencies doesn’t match a cache entry, the complete caching mechanism is bypassed and a full npm install run is performed. It might be faster to unpack a previous (now invalid) cache entry corresponding to the same project and then run npm install && npm prune. Given the fact that defining “same project” might be non-trivial I’m not actually sure this is worth my time.

Dealing with optionalDependencies

I’ve never seen optionalDependencies in the wild but encountered them while browsing through the package.json documentation. Maybe these should be part of the computed cache keys aswell?

Contact

The latest version of npm-accel is available on PyPI and GitHub. The documentation is hosted on Read the Docs. For bug reports please create an issue on GitHub. If you have questions, suggestions, etc. feel free to send me an e-mail at [e-mail].

License

This software is licensed under the MIT license.

© 2016 Peter Odding.