add post about the upcoming docs.rs changes

Author: pietroalbini

posts/2019-09-18-upcoming-docsrs-changes.md

@@ -0,0 +1,85 @@
+---
+layout: post
+title: "Upcoming docs.rs changes"
+author: The Rust Infrastructure Team
+---
+
+On September 42nd breaking changes will be deployed to the [docs.rs] build
+environment. [docs.rs] is a free service building and hosting documentation for
+all the crates published on [crates.io]. It's [open source][docsrs-source] and
+maintained by the [Rustdoc team][rustdoc-team].
+
+## What will change
+
+Builds will be executed inside the [rustops/crates-build-env] Docker image.
+That image contains a lot of system dependencies installed to ensure we can
+build as many crates as possible. It's already used by [Crater], and we added
+all the dependencies previously installed in the legacy build environment.
+
+To ensure we can continue operating the service in the future and to increase
+its reliability we also improved the sandbox builds are executed into, adding
+new limits:
+
+* Each platform will now have **15 minutes** to build its dependencies and
+  documentation.
+* **3 GB of RAM** will be available for the build.
+* Network access will be completly **disabled**.
+* Only the `target/` directory will be writable, and it will be purged after
+  each build.
+
+Finally, docs.rs will now use the latest nightly available when building
+crates.
+
+## How to prepare for the changes
+
+To test if your crate builds inside the new environment you can download the
+Docker image locally and execute a shell inside it:
+
+```
+docker pull rustops/crates-build-env
+docker run --rm -it rustops/crates-build-env bash
+```
+
+Once you're in a shell you can install [rustup] (it's not installed in the
+image), install Rust nightly, clone your crate's repository and then build the
+documentation:
+
+```
+cargo doc --no-deps
+```
+
+If a dependency is missing please [open an issue][crates-build-env-issue] on
+the Docker image's repository.
+
+If your crate fails to build because it took more than 15 minutes to generate
+its docs or it uses more than 3 GB of RAM please [open an issue][docsrs-issue]
+and we will increase the limits for your crate (when it's reasonable). We will
+**not** enable network access for your crate though: you'll need to change your
+crate not to require any external resource at build time.
+
+## Acknowledgements
+
+The new build environment is based on [Rustwide], the library powering
+[Crater]. It was extracted from the Crater codebase, and created both by the
+[Crater contributors] and the [Rustwide contributors].
+
+The implementation work on the docs.rs side was done by [Pietro Albini][pietro]
+and [Onur Aslan][onur], with [QuietMisdreavus][misdreavus] and [Mark
+Rousskov][mark] reviewing the changes.
+
+[docs.rs]: https://docs.rs
+[crates.io]: https://crates.io
+[docsrs-source]: https://github.com/rust-lang/docs.rs
+[rustdoc-team]: https://www.rust-lang.org/governance/teams/dev-tools#rustdoc
+[rustops/crates-build-env]: https://hub.docker.com/r/rustops/crates-build-env
+[Crater]: https://github.com/rust-lang/crater
+[rustup]: https://rustup.rs
+[crates-build-env-issue]: https://github.com/rust-lang/crates-build-env/issues
+[docsrs-issue]: https://github.com/rust-lang/crates-build-env/issues
+[rustwide]: https://github.com/rust-lang/rustwide
+[Crater contributors]: https://github.com/rust-lang/crater/graphs/contributors
+[Rustwide contributors]: https://github.com/rust-lang/rustwide/graphs/contributors
+[pietro]: https://github.com/pietroalbini
+[onur]: https://github.com/onur
+[mark]: https://github.com/Mark-Simulacrum
+[misdreavus]: https://github.com/QuietMisdreavus