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//! A `Source` for registry-based packages. //! //! # What's a Registry? //! //! Registries are central locations where packages can be uploaded to, //! discovered, and searched for. The purpose of a registry is to have a //! location that serves as permanent storage for versions of a crate over time. //! //! Compared to git sources, a registry provides many packages as well as many //! versions simultaneously. Git sources can also have commits deleted through //! rebasings where registries cannot have their versions deleted. //! //! # The Index of a Registry //! //! One of the major difficulties with a registry is that hosting so many //! packages may quickly run into performance problems when dealing with //! dependency graphs. It's infeasible for cargo to download the entire contents //! of the registry just to resolve one package's dependencies, for example. As //! a result, cargo needs some efficient method of querying what packages are //! available on a registry, what versions are available, and what the //! dependencies for each version is. //! //! One method of doing so would be having the registry expose an HTTP endpoint //! which can be queried with a list of packages and a response of their //! dependencies and versions is returned. This is somewhat inefficient however //! as we may have to hit the endpoint many times and we may have already //! queried for much of the data locally already (for other packages, for //! example). This also involves inventing a transport format between the //! registry and Cargo itself, so this route was not taken. //! //! Instead, Cargo communicates with registries through a git repository //! referred to as the Index. The Index of a registry is essentially an easily //! query-able version of the registry's database for a list of versions of a //! package as well as a list of dependencies for each version. //! //! Using git to host this index provides a number of benefits: //! //! * The entire index can be stored efficiently locally on disk. This means //! that all queries of a registry can happen locally and don't need to touch //! the network. //! //! * Updates of the index are quite efficient. Using git buys incremental //! updates, compressed transmission, etc for free. The index must be updated //! each time we need fresh information from a registry, but this is one //! update of a git repository that probably hasn't changed a whole lot so //! it shouldn't be too expensive. //! //! Additionally, each modification to the index is just appending a line at //! the end of a file (the exact format is described later). This means that //! the commits for an index are quite small and easily applied/compressable. //! //! ## The format of the Index //! //! The index is a store for the list of versions for all packages known, so its //! format on disk is optimized slightly to ensure that `ls registry` doesn't //! produce a list of all packages ever known. The index also wants to ensure //! that there's not a million files which may actually end up hitting //! filesystem limits at some point. To this end, a few decisions were made //! about the format of the registry: //! //! 1. Each crate will have one file corresponding to it. Each version for a //! crate will just be a line in this file. //! 2. There will be two tiers of directories for crate names, under which //! crates corresponding to those tiers will be located. //! //! As an example, this is an example hierarchy of an index: //! //! ```notrust //! . //! ├── 3 //! │ └── u //! │ └── url //! ├── bz //! │ └── ip //! │ └── bzip2 //! ├── config.json //! ├── en //! │ └── co //! │ └── encoding //! └── li //! ├── bg //! │ └── libgit2 //! └── nk //! └── link-config //! ``` //! //! The root of the index contains a `config.json` file with a few entries //! corresponding to the registry (see `RegistryConfig` below). //! //! Otherwise, there are three numbered directories (1, 2, 3) for crates with //! names 1, 2, and 3 characters in length. The 1/2 directories simply have the //! crate files underneath them, while the 3 directory is sharded by the first //! letter of the crate name. //! //! Otherwise the top-level directory contains many two-letter directory names, //! each of which has many sub-folders with two letters. At the end of all these //! are the actual crate files themselves. //! //! The purpose of this layout is to hopefully cut down on `ls` sizes as well as //! efficient lookup based on the crate name itself. //! //! ## Crate files //! //! Each file in the index is the history of one crate over time. Each line in //! the file corresponds to one version of a crate, stored in JSON format (see //! the `RegistryPackage` structure below). //! //! As new versions are published, new lines are appended to this file. The only //! modifications to this file that should happen over time are yanks of a //! particular version. //! //! # Downloading Packages //! //! The purpose of the Index was to provide an efficient method to resolve the //! dependency graph for a package. So far we only required one network //! interaction to update the registry's repository (yay!). After resolution has //! been performed, however we need to download the contents of packages so we //! can read the full manifest and build the source code. //! //! To accomplish this, this source's `download` method will make an HTTP //! request per-package requested to download tarballs into a local cache. These //! tarballs will then be unpacked into a destination folder. //! //! Note that because versions uploaded to the registry are frozen forever that //! the HTTP download and unpacking can all be skipped if the version has //! already been downloaded and unpacked. This caching allows us to only //! download a package when absolutely necessary. //! //! # Filesystem Hierarchy //! //! Overall, the `$HOME/.cargo` looks like this when talking about the registry: //! //! ```notrust //! # A folder under which all registry metadata is hosted (similar to //! # $HOME/.cargo/git) //! $HOME/.cargo/registry/ //! //! # For each registry that cargo knows about (keyed by hostname + hash) //! # there is a folder which is the checked out version of the index for //! # the registry in this location. Note that this is done so cargo can //! # support multiple registries simultaneously //! index/ //! registry1-<hash>/ //! registry2-<hash>/ //! ... //! //! # This folder is a cache for all downloaded tarballs from a registry. //! # Once downloaded and verified, a tarball never changes. //! cache/ //! registry1-<hash>/<pkg>-<version>.crate //! ... //! //! # Location in which all tarballs are unpacked. Each tarball is known to //! # be frozen after downloading, so transitively this folder is also //! # frozen once its unpacked (it's never unpacked again) //! src/ //! registry1-<hash>/<pkg>-<version>/... //! ... //! ``` use std::collections::HashMap; use std::fs::File; use std::path::{PathBuf, Path}; use flate2::read::GzDecoder; use tar::Archive; use core::{Source, SourceId, PackageId, Package, Summary, Registry}; use core::dependency::Dependency; use sources::PathSource; use util::{CargoResult, Config, internal, ChainError, FileLock, Filesystem}; use util::hex; const INDEX_LOCK: &'static str = ".cargo-index-lock"; pub static CRATES_IO: &'static str = "https://github.com/rust-lang/crates.io-index"; pub struct RegistrySource<'cfg> { source_id: SourceId, src_path: Filesystem, config: &'cfg Config, updated: bool, ops: Box<RegistryData + 'cfg>, index: index::RegistryIndex<'cfg>, index_locked: bool, } #[derive(Deserialize)] pub struct RegistryConfig { /// Download endpoint for all crates. This will be appended with /// `/<crate>/<version>/download` and then will be hit with an HTTP GET /// request to download the tarball for a crate. pub dl: String, /// API endpoint for the registry. This is what's actually hit to perform /// operations like yanks, owner modifications, publish new crates, etc. pub api: String, } #[derive(Deserialize)] struct RegistryPackage { name: String, vers: String, deps: Vec<RegistryDependency>, features: HashMap<String, Vec<String>>, cksum: String, yanked: Option<bool>, } #[derive(Deserialize)] struct RegistryDependency { name: String, req: String, features: Vec<String>, optional: bool, default_features: bool, target: Option<String>, kind: Option<String>, } pub trait RegistryData { fn index_path(&self) -> &Filesystem; fn config(&self) -> CargoResult<Option<RegistryConfig>>; fn update_index(&mut self) -> CargoResult<()>; fn download(&mut self, pkg: &PackageId, checksum: &str) -> CargoResult<FileLock>; } mod index; mod remote; mod local; fn short_name(id: &SourceId) -> String { let hash = hex::short_hash(id); let ident = id.url().host_str().unwrap_or("").to_string(); format!("{}-{}", ident, hash) } impl<'cfg> RegistrySource<'cfg> { pub fn remote(source_id: &SourceId, config: &'cfg Config) -> RegistrySource<'cfg> { let name = short_name(source_id); let ops = remote::RemoteRegistry::new(source_id, config, &name); RegistrySource::new(source_id, config, &name, Box::new(ops), true) } pub fn local(source_id: &SourceId, path: &Path, config: &'cfg Config) -> RegistrySource<'cfg> { let name = short_name(source_id); let ops = local::LocalRegistry::new(path, config, &name); RegistrySource::new(source_id, config, &name, Box::new(ops), false) } fn new(source_id: &SourceId, config: &'cfg Config, name: &str, ops: Box<RegistryData + 'cfg>, index_locked: bool) -> RegistrySource<'cfg> { RegistrySource { src_path: config.registry_source_path().join(name), config: config, source_id: source_id.clone(), updated: false, index: index::RegistryIndex::new(source_id, ops.index_path(), config, index_locked), index_locked: index_locked, ops: ops, } } /// Decode the configuration stored within the registry. /// /// This requires that the index has been at least checked out. pub fn config(&self) -> CargoResult<Option<RegistryConfig>> { self.ops.config() } /// Unpacks a downloaded package into a location where it's ready to be /// compiled. /// /// No action is taken if the source looks like it's already unpacked. fn unpack_package(&self, pkg: &PackageId, tarball: &FileLock) -> CargoResult<PathBuf> { let dst = self.src_path.join(&format!("{}-{}", pkg.name(), pkg.version())); dst.create_dir()?; // Note that we've already got the `tarball` locked above, and that // implies a lock on the unpacked destination as well, so this access // via `into_path_unlocked` should be ok. let dst = dst.into_path_unlocked(); let ok = dst.join(".cargo-ok"); if ok.exists() { return Ok(dst) } let gz = GzDecoder::new(tarball.file())?; let mut tar = Archive::new(gz); tar.unpack(dst.parent().unwrap())?; File::create(&ok)?; Ok(dst) } fn do_update(&mut self) -> CargoResult<()> { self.ops.update_index()?; let path = self.ops.index_path(); self.index = index::RegistryIndex::new(&self.source_id, path, self.config, self.index_locked); Ok(()) } } impl<'cfg> Registry for RegistrySource<'cfg> { fn query(&mut self, dep: &Dependency) -> CargoResult<Vec<Summary>> { // If this is a precise dependency, then it came from a lockfile and in // theory the registry is known to contain this version. If, however, we // come back with no summaries, then our registry may need to be // updated, so we fall back to performing a lazy update. if dep.source_id().precise().is_some() && !self.updated { if self.index.query(dep)?.is_empty() { self.do_update()?; } } self.index.query(dep) } fn supports_checksums(&self) -> bool { true } } impl<'cfg> Source for RegistrySource<'cfg> { fn source_id(&self) -> &SourceId { &self.source_id } fn update(&mut self) -> CargoResult<()> { // If we have an imprecise version then we don't know what we're going // to look for, so we always attempt to perform an update here. // // If we have a precise version, then we'll update lazily during the // querying phase. Note that precise in this case is only // `Some("locked")` as other `Some` values indicate a `cargo update // --precise` request if self.source_id.precise() != Some("locked") { self.do_update()?; } Ok(()) } fn download(&mut self, package: &PackageId) -> CargoResult<Package> { let hash = self.index.hash(package)?; let path = self.ops.download(package, &hash)?; let path = self.unpack_package(package, &path).chain_error(|| { internal(format!("failed to unpack package `{}`", package)) })?; let mut src = PathSource::new(&path, &self.source_id, self.config); src.update()?; let pkg = src.download(package)?; // Unfortunately the index and the actual Cargo.toml in the index can // differ due to historical Cargo bugs. To paper over these we trash the // *summary* loaded from the Cargo.toml we just downloaded with the one // we loaded from the index. let summaries = self.index.summaries(package.name())?; let summary = summaries.iter().map(|s| &s.0).find(|s| { s.package_id() == package }).expect("summary not found"); let mut manifest = pkg.manifest().clone(); manifest.set_summary(summary.clone()); Ok(Package::new(manifest, pkg.manifest_path())) } fn fingerprint(&self, pkg: &Package) -> CargoResult<String> { Ok(pkg.package_id().version().to_string()) } }