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//! Access to a Git index based registry. See [`RemoteRegistry`] for details.
use crate::core::global_cache_tracker;
use crate::core::{GitReference, PackageId, SourceId};
use crate::sources::git;
use crate::sources::git::fetch::RemoteKind;
use crate::sources::git::resolve_ref;
use crate::sources::registry::download;
use crate::sources::registry::MaybeLock;
use crate::sources::registry::{LoadResponse, RegistryConfig, RegistryData};
use crate::util::cache_lock::CacheLockMode;
use crate::util::errors::CargoResult;
use crate::util::interning::InternedString;
use crate::util::{Filesystem, GlobalContext};
use anyhow::Context as _;
use cargo_util::paths;
use lazycell::LazyCell;
use std::cell::{Cell, Ref, RefCell};
use std::fs::File;
use std::mem;
use std::path::Path;
use std::str;
use std::task::{ready, Poll};
use tracing::{debug, trace};
/// A remote registry is a registry that lives at a remote URL (such as
/// crates.io). The git index is cloned locally, and `.crate` files are
/// downloaded as needed and cached locally.
///
/// This type is primarily accessed through the [`RegistryData`] trait.
///
/// See the [module-level documentation](super) for the index format and layout.
///
/// ## History of Git-based index registry
///
/// Using Git to host this index used to be quite efficient. The full index can
/// be stored efficiently locally on disk, and once it is downloaded, all
/// queries of a registry can happen locally and needn't touch the network.
/// Git-based index was a reasonable design choice at the time when HTTP/2
/// was just introduced.
///
/// However, the full index keeps growing as crates.io grows. It becomes
/// relatively big and slows down the first use of Cargo. Git (specifically
/// libgit2) is not efficient at handling huge amounts of small files either.
/// On the other hand, newer protocols like HTTP/2 are prevalent and capable to
/// serve a bunch of tiny files. Today, it is encouraged to use [`HttpRegistry`],
/// which is the default from 1.70.0. That being said, Cargo will continue
/// supporting Git-based index for a pretty long while.
///
/// [`HttpRegistry`]: super::http_remote::HttpRegistry
pub struct RemoteRegistry<'gctx> {
/// The name of this source, a unique string (across all sources) used as
/// the directory name where its cached content is stored.
name: InternedString,
/// Path to the registry index (`$CARGO_HOME/registry/index/$REG-HASH`).
index_path: Filesystem,
/// Path to the cache of `.crate` files (`$CARGO_HOME/registry/cache/$REG-HASH`).
cache_path: Filesystem,
/// The unique identifier of this registry source.
source_id: SourceId,
/// This reference is stored so that when a registry needs update, it knows
/// where to fetch from.
index_git_ref: GitReference,
gctx: &'gctx GlobalContext,
/// A Git [tree object] to help this registry find crate metadata from the
/// underlying Git repository.
///
/// This is stored here to prevent Git from repeatedly creating a tree object
/// during each call into `load()`.
///
/// [tree object]: https://git-scm.com/book/en/v2/Git-Internals-Git-Objects#_tree_objects
tree: RefCell<Option<git2::Tree<'static>>>,
/// A Git repository that contains the actual index we want.
repo: LazyCell<git2::Repository>,
/// The current HEAD commit of the underlying Git repository.
head: Cell<Option<git2::Oid>>,
/// This stores sha value of the current HEAD commit for convenience.
current_sha: Cell<Option<InternedString>>,
/// Whether this registry needs to update package information.
///
/// See [`RemoteRegistry::mark_updated`] on how to make sure a registry
/// index is updated only once per session.
needs_update: bool,
/// Disables status messages.
quiet: bool,
}
impl<'gctx> RemoteRegistry<'gctx> {
/// Creates a Git-rebased remote registry for `source_id`.
///
/// * `name` --- Name of a path segment where `.crate` tarballs and the
/// registry index are stored. Expect to be unique.
pub fn new(
source_id: SourceId,
gctx: &'gctx GlobalContext,
name: &str,
) -> RemoteRegistry<'gctx> {
RemoteRegistry {
name: name.into(),
index_path: gctx.registry_index_path().join(name),
cache_path: gctx.registry_cache_path().join(name),
source_id,
gctx,
index_git_ref: GitReference::DefaultBranch,
tree: RefCell::new(None),
repo: LazyCell::new(),
head: Cell::new(None),
current_sha: Cell::new(None),
needs_update: false,
quiet: false,
}
}
/// Creates intermediate dirs and initialize the repository.
fn repo(&self) -> CargoResult<&git2::Repository> {
self.repo.try_borrow_with(|| {
trace!("acquiring registry index lock");
let path = self
.gctx
.assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);
match git2::Repository::open(&path) {
Ok(repo) => Ok(repo),
Err(_) => {
drop(paths::remove_dir_all(&path));
paths::create_dir_all(&path)?;
// Note that we'd actually prefer to use a bare repository
// here as we're not actually going to check anything out.
// All versions of Cargo, though, share the same CARGO_HOME,
// so for compatibility with older Cargo which *does* do
// checkouts we make sure to initialize a new full
// repository (not a bare one).
//
// We should change this to `init_bare` whenever we feel
// like enough time has passed or if we change the directory
// that the folder is located in, such as by changing the
// hash at the end of the directory.
//
// Note that in the meantime we also skip `init.templatedir`
// as it can be misconfigured sometimes or otherwise add
// things that we don't want.
let mut opts = git2::RepositoryInitOptions::new();
opts.external_template(false);
Ok(git2::Repository::init_opts(&path, &opts).with_context(|| {
format!("failed to initialize index git repository (in {:?})", path)
})?)
}
}
})
}
/// Get the object ID of the HEAD commit from the underlying Git repository.
fn head(&self) -> CargoResult<git2::Oid> {
if self.head.get().is_none() {
let repo = self.repo()?;
let oid = resolve_ref(&self.index_git_ref, repo)?;
self.head.set(Some(oid));
}
Ok(self.head.get().unwrap())
}
/// Returns a [`git2::Tree`] object of the current HEAD commit of the
/// underlying Git repository.
fn tree(&self) -> CargoResult<Ref<'_, git2::Tree<'_>>> {
{
let tree = self.tree.borrow();
if tree.is_some() {
return Ok(Ref::map(tree, |s| s.as_ref().unwrap()));
}
}
let repo = self.repo()?;
let commit = repo.find_commit(self.head()?)?;
let tree = commit.tree()?;
// SAFETY:
// Unfortunately in libgit2 the tree objects look like they've got a
// reference to the repository object which means that a tree cannot
// outlive the repository that it came from. Here we want to cache this
// tree, though, so to accomplish this we transmute it to a static
// lifetime.
//
// Note that we don't actually hand out the static lifetime, instead we
// only return a scoped one from this function. Additionally the repo
// we loaded from (above) lives as long as this object
// (`RemoteRegistry`) so we then just need to ensure that the tree is
// destroyed first in the destructor, hence the destructor on
// `RemoteRegistry` below.
let tree = unsafe { mem::transmute::<git2::Tree<'_>, git2::Tree<'static>>(tree) };
*self.tree.borrow_mut() = Some(tree);
Ok(Ref::map(self.tree.borrow(), |s| s.as_ref().unwrap()))
}
/// Gets the current version of the registry index.
///
/// It is usually sha of the HEAD commit from the underlying Git repository.
fn current_version(&self) -> Option<InternedString> {
if let Some(sha) = self.current_sha.get() {
return Some(sha);
}
let sha = InternedString::new(&self.head().ok()?.to_string());
self.current_sha.set(Some(sha));
Some(sha)
}
/// Whether the registry is up-to-date. See [`Self::mark_updated`] for more.
fn is_updated(&self) -> bool {
self.gctx.updated_sources().contains(&self.source_id)
}
/// Marks this registry as up-to-date.
///
/// This makes sure the index is only updated once per session since it is
/// an expensive operation. This generally only happens when the resolver
/// is run multiple times, such as during `cargo publish`.
fn mark_updated(&self) {
self.gctx.updated_sources().insert(self.source_id);
}
}
impl<'gctx> RegistryData for RemoteRegistry<'gctx> {
fn prepare(&self) -> CargoResult<()> {
self.repo()?;
self.gctx
.deferred_global_last_use()?
.mark_registry_index_used(global_cache_tracker::RegistryIndex {
encoded_registry_name: self.name,
});
Ok(())
}
fn index_path(&self) -> &Filesystem {
&self.index_path
}
fn assert_index_locked<'a>(&self, path: &'a Filesystem) -> &'a Path {
self.gctx
.assert_package_cache_locked(CacheLockMode::DownloadExclusive, path)
}
/// Read the general concept for `load()` on [`RegistryData::load`].
///
/// `index_version` is a string representing the version of the file used
/// to construct the cached copy.
///
/// Older versions of Cargo used the single value of the hash of the HEAD
/// commit as a `index_version`. This is technically correct but a little
/// too conservative. If a new commit is fetched all cached files need to
/// be regenerated even if a particular file was not changed.
///
/// However if an old cargo has written such a file we still know how to
/// read it, as long as we check for that hash value.
///
/// Cargo now uses a hash of the file's contents as provided by git.
fn load(
&mut self,
_root: &Path,
path: &Path,
index_version: Option<&str>,
) -> Poll<CargoResult<LoadResponse>> {
if self.needs_update {
return Poll::Pending;
}
// Check if the cache is valid.
let git_commit_hash = self.current_version();
if index_version.is_some() && index_version == git_commit_hash.as_deref() {
// This file was written by an old version of cargo, but it is
// still up-to-date.
return Poll::Ready(Ok(LoadResponse::CacheValid));
}
// Note that the index calls this method and the filesystem is locked
// in the index, so we don't need to worry about an `update_index`
// happening in a different process.
fn load_helper(
registry: &RemoteRegistry<'_>,
path: &Path,
index_version: Option<&str>,
) -> CargoResult<LoadResponse> {
let repo = registry.repo()?;
let tree = registry.tree()?;
let entry = tree.get_path(path);
let entry = entry?;
let git_file_hash = Some(entry.id().to_string());
// Check if the cache is valid.
if index_version.is_some() && index_version == git_file_hash.as_deref() {
return Ok(LoadResponse::CacheValid);
}
let object = entry.to_object(repo)?;
let Some(blob) = object.as_blob() else {
anyhow::bail!("path `{}` is not a blob in the git repo", path.display())
};
Ok(LoadResponse::Data {
raw_data: blob.content().to_vec(),
index_version: git_file_hash,
})
}
match load_helper(&self, path, index_version) {
Ok(result) => Poll::Ready(Ok(result)),
Err(_) if !self.is_updated() => {
// If git returns an error and we haven't updated the repo,
// return pending to allow an update to try again.
self.needs_update = true;
Poll::Pending
}
Err(e)
if e.downcast_ref::<git2::Error>()
.map(|e| e.code() == git2::ErrorCode::NotFound)
.unwrap_or_default() =>
{
// The repo has been updated and the file does not exist.
Poll::Ready(Ok(LoadResponse::NotFound))
}
Err(e) => Poll::Ready(Err(e)),
}
}
fn config(&mut self) -> Poll<CargoResult<Option<RegistryConfig>>> {
debug!("loading config");
self.prepare()?;
self.gctx
.assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);
match ready!(self.load(Path::new(""), Path::new(RegistryConfig::NAME), None)?) {
LoadResponse::Data { raw_data, .. } => {
trace!("config loaded");
let cfg: RegistryConfig = serde_json::from_slice(&raw_data)?;
Poll::Ready(Ok(Some(cfg)))
}
_ => Poll::Ready(Ok(None)),
}
}
fn block_until_ready(&mut self) -> CargoResult<()> {
if !self.needs_update {
return Ok(());
}
self.needs_update = false;
if self.is_updated() {
return Ok(());
}
self.mark_updated();
if self.gctx.offline() {
return Ok(());
}
if self.gctx.cli_unstable().no_index_update {
return Ok(());
}
debug!("updating the index");
// Ensure that we'll actually be able to acquire an HTTP handle later on
// once we start trying to download crates. This will weed out any
// problems with `.cargo/config` configuration related to HTTP.
//
// This way if there's a problem the error gets printed before we even
// hit the index, which may not actually read this configuration.
self.gctx.http()?;
self.prepare()?;
self.head.set(None);
*self.tree.borrow_mut() = None;
self.current_sha.set(None);
let _path = self
.gctx
.assert_package_cache_locked(CacheLockMode::DownloadExclusive, &self.index_path);
if !self.quiet {
self.gctx
.shell()
.status("Updating", self.source_id.display_index())?;
}
// Fetch the latest version of our `index_git_ref` into the index
// checkout.
let url = self.source_id.url();
let repo = self.repo.borrow_mut().unwrap();
git::fetch(
repo,
url.as_str(),
&self.index_git_ref,
self.gctx,
RemoteKind::Registry,
)
.with_context(|| format!("failed to fetch `{}`", url))?;
Ok(())
}
/// Read the general concept for `invalidate_cache()` on
/// [`RegistryData::invalidate_cache`].
///
/// To fully invalidate, undo [`RemoteRegistry::mark_updated`]'s work.
fn invalidate_cache(&mut self) {
self.needs_update = true;
}
fn set_quiet(&mut self, quiet: bool) {
self.quiet = quiet;
}
fn is_updated(&self) -> bool {
self.is_updated()
}
fn download(&mut self, pkg: PackageId, checksum: &str) -> CargoResult<MaybeLock> {
let registry_config = loop {
match self.config()? {
Poll::Pending => self.block_until_ready()?,
Poll::Ready(cfg) => break cfg.unwrap(),
}
};
download::download(
&self.cache_path,
&self.gctx,
self.name,
pkg,
checksum,
registry_config,
)
}
fn finish_download(
&mut self,
pkg: PackageId,
checksum: &str,
data: &[u8],
) -> CargoResult<File> {
download::finish_download(
&self.cache_path,
&self.gctx,
self.name.clone(),
pkg,
checksum,
data,
)
}
fn is_crate_downloaded(&self, pkg: PackageId) -> bool {
download::is_crate_downloaded(&self.cache_path, &self.gctx, pkg)
}
}
/// Implemented to just be sure to drop `tree` field before our other fields.
/// See SAFETY inside [`RemoteRegistry::tree()`] for more.
impl<'gctx> Drop for RemoteRegistry<'gctx> {
fn drop(&mut self) {
self.tree.borrow_mut().take();
}
}