0b05d4aefe
Summary: Add a pool of `Multi` handles that the client can reuse across requests. Previously, `HttpClient`'s async functions had to consume the client in order to have a `'static` lifetime (since `Future`s generally cannot hold references to things outside of themselves). This meant that the each async operation would use its own `Multi` handle, preventing connection reuse across operations since the `Multi` handle maintains a connection cache internally. With this change, the client can reuse the `Multi` session after an async operation, thereby benefitting from libcurl's caching. Note that the same `Multi` handle still cannot be used by concurrently running `Future`s (as this [would not be thread safe](https://curl.haxx.se/libcurl/c/threadsafe.html)), but once a `Future` has completed its `Multi` handle will return to the pool for use by subsequent requests. --- (Somewhat tangential) As is noted in the code comments, `libcurl`'s C API provides a way to share caches across multiple multi sessions: [the "share" interface](https://curl.haxx.se/libcurl/c/libcurl-share.html). While using this would seems preferable to an ad-hoc solution like this diff, it turns out that the `curl` crate does not provide safe bindings to the share interface. This means that in order to use the share interface, we'd need to directly use the unsafe bindings from `curl-sys`. In addition to the difficulty of working with unsafe FFI code, the API expects the application to handle synchronization by passing it function pointers to handle locking/unlocking shared resources. Ultimately, I came to the conclusion that managing lifetimes and synchronization in unsafe code across an FFI boundary would be nontrivial, and ensuring correctness would require a lot of effort that could be avoided by implementing an ad-hoc solution on top of the safe API instead. However, it might make sense to change this to use the share interface in the future. Reviewed By: quark-zju Differential Revision: D22396026 fbshipit-source-id: 06eea2ffacdc791527eac9ce4becc457af5c0480 |
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.github/workflows | ||
build | ||
CMake | ||
common | ||
configerator/structs/scm/mononoke | ||
eden | ||
.gitignore | ||
.projectid | ||
.travis.yml | ||
build.bat | ||
build.sh | ||
CMakeLists.txt | ||
CODE_OF_CONDUCT.md | ||
CONTRIBUTING.md | ||
LICENSE | ||
make-client.py | ||
README.md | ||
rustfmt.toml |
EdenSCM
EdenSCM is a cross-platform, highly scalable source control management system.
It aims to provide both user-friendly and powerful interfaces for users, as well as extreme scalability to deal with repositories containing many millions of files and many millions of commits.
EdenSCM is comprised of three main components:
- The
eden
CLI: The client-side command line interface for users to interact with EdenSCM. - Mononoke: The server-side part of EdenSCM.
- EdenFS: A virtual filesystem for efficiently checking out large repositories.
EdenSCM's scalability goals are to ensure that all source control operations scale with the number of files in use by a developer, and not with the size of the repository itself. This enables fast, performant developer experiences even in massive repositories with many long files and very long commit histories.
The eden
CLI
The eden
CLI was originally based on
Mercurial, and shares many aspects of the UI
and features of Mercurial.
The CLI code can be found in the eden/scm
subdirectory.
Building the eden
CLI
The eden
CLI currently builds and runs on Linux, Mac, and Windows. The
setup.py
script is the main interface for building the CLI.
Mononoke
Mononoke is the server-side component of EdenSCM.
Despite having originally evolved from Mercurial, EdenSCM is not a distributed source control system. In order to support massive repositories, not all repository data is downloaded to the client system when checking out a repository. Clients ideally only download the minimal amount of data necessary, and then fetch additional data from the server as it is needed.
Building Mononoke
The Mononoke code lives under eden/mononoke
Mononoke currently builds and runs only on Linux, and is not yet buildable
outside of Facebook's internal environment. Work is still in progress to
support building Mononoke with Rust's cargo
build system.
EdenFS
EdenFS is a virtual file system for managing EdenSCM checkouts.
EdenFS speeds up operations in large repositories by only populating working
directory files on demand, as they are accessed. This makes operations like
checkout
much faster, in exchange for a small performance hit when first
accessing new files. This is quite beneficial in large repositories where
developers often only work with a small subset of the repository at a time.
EdenFS has similar performance advantages to using sparse checkouts, but a much better user experience. Unlike with sparse checkouts, EdenFS does not require manually curating the list of files to check out, and users can transparently access any file without needing to update the profile.
EdenFS also keeps track of which files have been modified, allowing very
efficient status
queries that do not need to scan the working directory.
The filesystem monitoring tool Watchman
also integrates with EdenFS, allowing it to more efficiently track updates to
the filesystem.
More detailed EdenFS design documentation can be found at eden/fs/docs/Overview.md.
Building EdenFS
EdenFS currently builds on Linux, Mac, and Windows.
The recommended way to build EdenFS is using the build.sh
script in the
top-level of the repository. This script will download and build all of the
necessary dependencies for EdenFS, before building EdenFS itself. On Windows
use the build.bat
script instead of build.sh
.
This build script will create an output directory outside of the repository
where it will perform the build. You can control this output directory
location by passing a --scratch-path
argument to the build script.
Support
EdenSCM is the primary source control system used at Facebook, and is used for Facebook's main monorepo code base.
Support for using EdenSCM outside of Facebook is still highly experimental. While we would be interested to hear feedback if you run into issues, supporting external users is not currently a high priority for the development team, so we unfortunately cannot guarantee prompt support at this time.
License
See LICENSE.