Cachi2

Cachi2 is a CLI tool that pre-fetches your project's dependencies to aid in making your build process hermetic.

To see if we support your package manager(s), please check the package managers section.

The primary intended use of Cachi2's outputs is for network-isolated container builds (see usage).

Table of contents

• Goals
• Installation
• Basic usage
• Configuration
• Releasing
• Package managers
• Project status
• Contributing

Goals

Please note that Cachi2 is rather picky, aiming to:

• encourage or enforce best practices
• never execute arbitrary code - looking at you setup.py (discouraged)
• keep the implementation simple

To play nicely with Cachi2, the build process for your project must be

• Defined - Cachi2 only fetches dependencies that are explicitly declared - typically in a lockfile generated by your package manager.

• Reproducible - Cachi2 will refuse to fetch a dependency if it's not pinned to an exact version. This goes for transitive dependencies as well (and ties to the Defined point). Most package managers pin all dependencies automatically in lockfiles.

• Secure - Even with a lockfile, your build is not truly safe from supply chain attacks (such as dependency confusion) unless you verify the checksums of all dependencies. If your package manager supports specifying the expected checksums, we strongly encourage you to make use of them.

  ⚠ Cachi2 will verify checksums if present, but doesn't require them by default. This may change in the future.

In return, Cachi2 will help make your build

• Auditable - by generating a manifest of all the dependencies that go into your build.

The ability to achieve the goals depends on the hermeticity of the build process. Ideally, you should try to isolate the build from both the internet and the underlying host system to avoid implicit dependencies, irreproducible behavior and whole hosts of other issues. Cachi2 itself is not a hermetic build system. We suggest you take advantage of existing technologies - such as containers - to achieve isolation (see usage).

Installation

Standalone

We do not distribute Cachi2 as a standalone package as of now.

To install Cachi2 for local development, see the development section.

Container image

quay.io/redhat-appstudio/cachi2:latest

The container is re-built automatically on every merge to the main branch.

You may wish to set up an alias to make local usage more convenient:

alias cachi2='podman run --rm -ti -v "$PWD:$PWD:z" -w "$PWD" quay.io/redhat-appstudio/cachi2:latest'

Note that the alias mounts the current working directory - the container will have access to files in that directory and nowhere else.

Basic usage

cachi2 fetch-deps \
  --source ./my-repo \
  --output ./cachi2-output \
  gomod

The fetch-deps command fetches your project's dependencies and stores them on your disk. You can then use these outputs to, say, build a container image.

See docs/usage.md for a more detailed, practical (cough) example of Cachi2 usage.

You might also like to check out cachi2 --help and the --help texts of the available subcommands.

Configuration

You can change Cachi2's configuration by specifying a configuration file while invoking any of the CLI commands:

 cachi2 --config-file config.yaml fetch-deps --source ./my-repo gomod

Any parameter specified in this file will override the default values present in the config.py module.

The only supported format for the config file is YAML.

Available configuration parameters

• default_environment_variables - a dictionary where the keys are names of package managers. The values are dictionaries where the keys are default environment variables to set for that package manager and the values are the environment variable values.
• gomod_download_max_tries - a maximum number of attempts for retrying go commands.
• gomod_strict_vendor - (deprecated) the bool to disable/enable the strict vendor mode. For a repo that has gomod dependencies, if the vendor directory exists and this config option is set to True, one of the vendoring flags must be used. This option no longer has any effect when set. Check the vendoring docs for more information.
• goproxy_url - sets the value of the GOPROXY variable that Cachi2 uses internally when downloading Go modules. See Go environment variables.
• requests_timeout - a number (in seconds) for requests.get()'s 'timeout' parameter, which sets an upper limit on how long requests can take to make a connection and/or send a response. Larger numbers set longer timeouts.
• subprocess_timeout - a number (in seconds) to set a timeout for commands executed by the subprocess module. Set a larger number to give the subprocess execution more time.

Package managers

Supported:

• gomod
• pip
• npm
• yarn
• bundler

Experimental:

• generic fetcher

Planned:

• dnf
• cargo

Based on the supported package managers in the original Cachito.

gomod

https://go.dev/ref/mod

Current version: 1.23 ^{1 2 3}

The gomod package manager works by parsing the go.mod file present in the source repository to determine which dependencies to download. Cachi2 does not parse this file on its own - rather, we rely on the go command to download and list the required dependencies.

From go 1.17 onward, the go.mod file includes all the transitively required dependencies of your application - see the section about Pruned module graphs in the 1.17 changelog. In previous go versions, the go.mod file included only direct dependencies. Cachi2 does support downloading and listing all transitive dependencies for earlier versions thanks to Go's backwards compatibility². Note that using go >= 1.17 in your project has the added benefit of downloading fewer dependencies (as noted in the changelog), in some cases drastically so.

See docs/gomod.md for more details.

pip

https://pip.pypa.io/en/stable/

Cachi2 supports pip by parsing requirements.txt files present in the source repository and downloading the declared dependencies.

The files must be lockfiles, i.e. declare all the transitive dependencies and pin them to specific versions. Generating such a lockfile is best done using tools like pip-compile.

We support source distribution file format (sdist) as well as binary distribution file format (wheel).

See docs/pip.md for more details.

npm

https://docs.npmjs.com/

Cachi2 supports npm by parsing package-lock.json file present in the source repository and downloading the declared dependencies.

To generate lockfile or to make sure the file is up to date, you can use npm install.

Make sure lockfile version is higher than v1 (Node.js 15 or higher).

See docs/npm.md for more details.

yarn

https://v3.yarnpkg.com/

Current version: v3

Unlike NPM, cachi2 merely drives the underlying yarn CLI command operations, that is, cachi2 leaves most of the heavy lifting to Yarn itself and it mainly focuses on post-process validation. Note that having a Yarn lockfile (yarn.lock) checked into the repository is paramount for cachi2 to process a project successfully. If missing, you can easily generate one by running yarn install prior to pointing cachi2 to your project.

See docs/yarn.md for more details.

bundler

https://bundler.io/

Cachi2 supports bundler by parsing the Gemfile.lock file present in the source repository and downloading the declared dependencies.

To generate a lockfile or to make sure the file is up to date, you can use for example the bundle lock command, which generates the Gemfile.lock file based on the dependencies specified in the Gemfile. Both files must be present in the source repository so you should check them into your git repository.

See docs/bundler.md for more details.

generic fetcher

Generic fetcher is a way for Cachi2 to support prefetching arbitrary files that don't fit into other package managers. With the generic fetcher, you can easily fetch those files with Cachi2 along with your other language-specific dependencies, satisfy the hermetic build condition and have them recorded in the SBOM.

Cachi2 uses a simple custom lockfile named generic_lockfile.yaml that is expected to be present in the repository. The lockfile describes the urls, checksums and target locations for the downloaded files. The generic fetcher is currently an experimental feature, so cachi2 has to be run with --dev-package-managers flag.

See docs/usage.md for more details.

Project status

Cachi2 was derived (but is not a direct fork) from Cachito and is still in early development phase.

Footnotes

1. Cachi2 expects to use a specific version of the go command when downloading dependencies. This is the version installed in the cachi2 container. We do not guarantee correctness if you run Cachi2 locally (outside the container) with a different Go version. You are free to use a different version to build your project. ↩

2. The go command promises to be backwards compatible with previous versions. If your go.mod file specifies the intended go version, Cachi2 should handle it appropriately. If your go version is higher than what Cachi2 uses, there is a good chance it will be compatible regardless, as long as the dependency resolution did not change between the two versions. For example, dependency resolution did change in go 1.18 but not in go 1.19. Things are a bit more complicated with Go 1.21, if you are or have been experiencing issues with cachi2 related to Go 1.21+, please refer to docs/gomod.md. ↩ ↩²

3. Although Cachi2 supports Go 1.23, support for workspace vendoring introduced in Go 1.22 hasn't been added yet (still in development) and so if your project makes use of the feature cachi2 will error out. ↩