v8-compile-cache

What is v8-compile-cache?

The v8-compile-cache package leverages V8's code caching capabilities to significantly speed up loading time of JavaScript modules in Node.js. By caching the compiled code of modules, it reduces the overhead of parsing and compiling scripts on every execution, leading to faster startup times for applications.

What are v8-compile-cache's main functionalities?

Enabling V8 Compile Cache

This is the basic usage to enable V8 compile cache in a Node.js application. By simply requiring the package at the beginning of your main script, it automatically hooks into the require system to cache compiled modules.

require('v8-compile-cache');

Other packages similar to v8-compile-cache

@babel/register

Similar to v8-compile-cache, @babel/register compiles your files on the fly. However, it focuses on transforming ES6+ code into backward-compatible JavaScript, rather than caching compiled code for performance.

pirates

Pirates provides a simple API to add custom require hooks, which can be used for transpiling code on the fly, similar to what v8-compile-cache does. However, it doesn't cache the compiled output by default, focusing instead on the transformation aspect.

README

v8-compile-cache

v8-compile-cache attaches a require hook to use V8's code cache to speed up instantiation time. The "code cache" is the work of parsing and compiling done by V8.

The ability to tap into V8 to produce/consume this cache was introduced in Node v5.7.0.

Usage

1. Add the dependency:

$ npm install --save v8-compile-cache

1. Then, in your entry module add:

require('v8-compile-cache');

Requiring v8-compile-cache in Node <5.7.0 is a noop – but you need at least Node 4.0.0 to support the ES2015 syntax used by v8-compile-cache.

Options

Set the environment variable DISABLE_V8_COMPILE_CACHE=1 to disable the cache.

Cache directory is defined by environment variable V8_COMPILE_CACHE_CACHE_DIR or defaults to <os.tmpdir()>/v8-compile-cache-<V8_VERSION>.

Internals

Cache files are suffixed .BLOB and .MAP corresponding to the entry module that required v8-compile-cache. The cache is entry module specific because it is faster to load the entire code cache into memory at once, than it is to read it from disk on a file-by-file basis.

Benchmarks

See https://github.com/zertosh/v8-compile-cache/tree/master/bench.

Load Times:

Module	Without Cache	With Cache
babel-core	218ms	185ms
yarn	153ms	113ms
yarn (bundled)	228ms	105ms

^ Includes the overhead of loading the cache itself.

Acknowledgements

• FileSystemBlobStore and NativeCompileCache are based on Atom's implementation of their v8 compile cache:
  • https://github.com/atom/atom/blob/b0d7a8a/src/file-system-blob-store.js
  • https://github.com/atom/atom/blob/b0d7a8a/src/native-compile-cache.js
• mkdirpSync is based on:
  • https://github.com/substack/node-mkdirp/blob/f2003bb/index.js#L55-L98