Contributing to the Software Delivery Stack

Overview

Software Delivery (SWD) Subsystems

Software Delivery Diagram

Major Binaries

Updated: September 2020

Subsystem	Purpose	Location	Language
amberctl	Deprecated CLI for various components. Scheduled to be replaced by `pkgctl`.	`//src/sys/pkg/bin/amber/amberctl`	Go
pkg-cache	Caches downloaded packages in case they are needed again.	`//src/sys/pkg/bin/pkg-cache`	Rust
pkg-resolver	Main entry point for software delivery stack. Coordinates retrieval and installation of packages.	`//src/sys/pkg/bin/pkg-resolver`	Rust
omaha-client	Checks for system updates using the Omaha server infrastructure	`//src/sys/pkg/bin/omaha-client`	Rust
pkgctl	CLI for pkg-resolver	`//src/sys/pkg/bin/pkgctl`	Rust
pkgfs	A filesystem for interacting with packages that are stored on a host.	`//src/sys/pkg/bin/pkgfs/pkgfs`	Go
system-ota-test	An end-to-end test of system over the air updates.	`//src/sys/pkg/tests/system-ota-tests`	Go
system-update-checker	Does what it says on the tin, checks for system updates!	`//src/sys/pkg/bin/system-update-checker`	Rust
system-updater	Actually performs system updates.	`//src/sys/pkg/bin/system-updater`	Rust

Key Dependencies

Useful Debugging Tools

fidlcat: it’s strace, but for every IPC on the system, not just syscalls.
zxdb: Fuchsia’s debugger. Similar usage to gdb, and has Unicode support (emoji!). Doesn’t currently work well with golang, but works fine with Rust.
Inspect: Opt-in APIs for components to expose aspects of their state. Several portions of the SWD stack implement this, and more to come.

IDEs

VS Code seems to work pretty well. Follow the instructions here, including any language-specific instructions you find relevant; the Rust instructions are a good place to start.

Style Guide

Use the style guide appropriate for the language you’re in. The SWD stack is mostly in Rust and Go, which have strong opinions about style. All commits in those languages should be formatted with rustfmt and gofmt respectively, and most editors/IDEs have a mode in which you can run those commands when you save a file. Do so!

Setup

Fuchsia Setup

Read the Fuchsia Getting Started guide first

Most of the SWD stack is in the base image of fuchsia, so to get a swd stack working with tests, your build configuration is quite simple:

First tests


Tab 1 > fx set core.x64 --with //bundles:tests && fx build && fx serve

Tab 2 > fx qemu -kN

Tab 3 > fx run-test pkg-resolver-integration-tests # example of running the pkg-resolver integration tests

For further info on fx workflows: https://fuchsia.dev/fuchsia-src/development/workflows/fx

More general tests

If you’ve successfully run the above, you have a working Fuchsia system with the software delivery stack working.

You can discover more tests with by running fx list-packages on the host.

Common Workflows

Updating a base image to get a new version of pkg-resolver or pkgctl

To update the base of your fuchsia image, you can use fx ota if you’re running on hardware which supports OTA. If you’re running under QEMU, you’ll need to just restart QEMU to get an updated base after a rebuild. Don’t worry, it’s fast.

Pulling down a new version of an external dependency

You’ll need to update that dependency’s vendored repository in //third_party. See the Rust documentation for examples.

Resolve a package and run a contained component

The package resolver is configured by default to resolve fuchsia.com to the local development host. To run a component in a package you’ve built locally, you can run something like fx shell run fuchsia-pkg://fuchsia.com/<package_name>#meta/<component_name>.cmx

TODO(wittrock): is there a global package repository we can use as a repo for this example?

FAQs

How do I run a hosted package server?

See the instructions on running a package repository with pm