8282c38fe0
Fixes #26179. The original error reported in that issue is fixed on canary, but in local testing on my windows machine, `next build` would just hang forever. After some digging, what happens is that at some point in next build, readFile promises (from `fs/promises` ) just never resolve, and so next hangs. It turns out the issue is saturating tokio's blocking task thread pool. We previously limited the number of blocking threads to 32, and at some point those threads are all in use and there's no thread available for the file reads. What's taking up all of those threads? The answer turns out to be `tokio::process`. On windows, child process stdio uses the blocking threadpool: https://github.com/tokio-rs/tokio/pull/4824. When you poll the child's stdio on windows, it spawns a blocking task per poll, and calls `std::io::Read::read` in the blocking context. That call can block until data is available. Putting it all together, what happens is that Next.js spawns `2 * the number of CPU cores` deno child subprocesses to do work. We implement `child_process` with `tokio::process`. When the child processes' stdio get polled, blocking tasks get spawned, and those blocking tasks might block until data is available. So if you have 16 cores (as I do), there are going to be potentially >32 blocking task threadpool threads taken just by the child processes. That leaves no room for other tasks to make progress --- To fix this, for now, increase the size of the blocking threadpool on windows. 4 * the number of CPU cores should be enough to leave room for other tasks to make progress. Longer term, this can be fixed more properly when we handroll our own subprocess code (needed for detached processes and additional pipes on windows). |
||
|---|---|---|
| .cargo | ||
| .devcontainer | ||
| .github | ||
| bench_util | ||
| cli | ||
| ext | ||
| resolvers | ||
| runtime | ||
| tests | ||
| tools | ||
| .dlint.json | ||
| .dprint.json | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| .gitmodules | ||
| .rustfmt.toml | ||
| Cargo.lock | ||
| Cargo.toml | ||
| import_map.json | ||
| LICENSE.md | ||
| README.md | ||
| Releases.md | ||
| rust-toolchain.toml | ||
Deno
Deno
(/ˈdiːnoʊ/, pronounced
dee-no) is a JavaScript, TypeScript, and WebAssembly runtime with secure
defaults and a great developer experience. It's built on V8,
Rust, and Tokio.
Learn more about the Deno runtime in the documentation.
Installation
Install the Deno runtime on your system using one of the commands below. Note that there are a number of ways to install Deno - a comprehensive list of installation options can be found here.
Shell (Mac, Linux):
curl -fsSL https://deno.land/install.sh | sh
PowerShell (Windows):
irm https://deno.land/install.ps1 | iex
Homebrew (Mac):
brew install deno
Chocolatey (Windows):
choco install deno
Build and install from source
Complete instructions for building Deno from source can be found in the manual here.
Your first Deno program
Deno can be used for many different applications, but is most commonly used to
build web servers. Create a file called server.ts and include the following
TypeScript code:
Deno.serve((_req: Request) => {
return new Response("Hello, world!");
});
Run your server with the following command:
deno run --allow-net server.ts
This should start a local web server on http://localhost:8000.
Learn more about writing and running Deno programs in the docs.
Additional resources
- Deno Docs: official guides and reference docs for the Deno runtime, Deno Deploy, and beyond.
- Deno Standard Library: officially supported common utilities for Deno programs.
- deno.land/x: registry for third-party Deno modules.
- Developer Blog: Product updates, tutorials, and more from the Deno team.
Contributing
We appreciate your help! To contribute, please read our contributing instructions.