| # v8-compile-cache-lib | |
| > Fork of [`v8-compile-cache`](https://www.npmjs.com/package/v8-compile-cache) exposed as an API for programmatic usage in other libraries and tools. | |
| --- | |
| [](https://github.com/cspotcode/v8-compile-cache-lib/actions?query=workflow%3A%22Continuous+Integration%22) | |
| `v8-compile-cache-lib` attaches a `require` hook to use [V8's code cache](https://v8project.blogspot.com/2015/07/code-caching.html) 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](https://nodejs.org/en/blog/release/v5.7.0/). | |
| ## Usage | |
| 1. Add the dependency: | |
| ```sh | |
| $ npm install --save v8-compile-cache-lib | |
| ``` | |
| 2. Then, in your entry module add: | |
| ```js | |
| require('v8-compile-cache-lib').install(); | |
| ``` | |
| **`.install()` 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-lib`.** | |
| ## 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-lib`. 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/cspotcode/v8-compile-cache-lib/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 | |
| * The original [`v8-compile-cache`](https://github.com/zertosh/v8-compile-cache) from which this library is forked. | |
| * `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 | |