# CI Scripts

This directory contains scripts for each build step in each build stage.

## Running a Stage Locally

Be aware that the tests will be built and run in-place, so please run at your own risk.
If the repository is not a fresh git clone, you might have to clean files from previous builds or test runs first.

The ci needs to perform various sysadmin tasks such as installing packages or writing to the user's home directory.
While it should be fine to run
the ci system locally on your development box, the ci scripts can generally be assumed to have received less review and
testing compared to other parts of the codebase. If you want to keep the work tree clean, you might want to run the ci
system in a virtual machine with a Linux operating system of your choice.

To allow for a wide range of tested environments, but also ensure reproducibility to some extent, the test stage
requires `bash`, `docker`, and `python3` to be installed. To run on different architectures than the host `qemu` is also required. To install all requirements on Ubuntu, run

```
sudo apt install bash docker.io python3 qemu-user-static
```

For some sanitizer builds, the kernel's address-space layout randomization
(ASLR) entropy can cause sanitizer shadow memory mappings to fail. When running
the CI locally you may need to reduce that entropy by running:

```
sudo sysctl -w vm.mmap_rnd_bits=28
```

To run a test that requires emulating a CPU architecture different from the
host, we may rely on the container environment recognizing foreign executables
and automatically running them using `qemu`. The following sets us up to do so
(also works for `podman`):

```
docker run --rm --privileged docker.io/multiarch/qemu-user-static --reset -p yes
```

It is recommended to run the CI system in a clean environment. The `env -i`
command below ensures that *only* specified environment variables are propagated
into the local CI.
To run the test stage with a specific configuration:

```
env -i HOME="$HOME" PATH="$PATH" USER="$USER" FILE_ENV="./ci/test/00_setup_env_arm.sh" ./ci/test_run_all.sh
```

## Configurations

The test files (`FILE_ENV`) are constructed to test a wide range of
configurations, rather than a single pass/fail. This helps to catch build
failures and logic errors that present on platforms other than the ones the
author has tested.

Some builders use the dependency-generator in `./depends`, rather than using
the system package manager to install build dependencies. This guarantees that
the tester is using the same versions as the release builds, which also use
`./depends`.

It is also possible to force a specific configuration without modifying the
file. For example,

```
env -i HOME="$HOME" PATH="$PATH" USER="$USER" MAKEJOBS="-j1" FILE_ENV="./ci/test/00_setup_env_arm.sh" ./ci/test_run_all.sh
```

The files starting with `0n` (`n` greater than 0) are the scripts that are run
in order.

## Cache

In order to avoid rebuilding all dependencies for each build, the binaries are
cached and reused when possible. Changes in the dependency-generator will
trigger cache-invalidation and rebuilds as necessary.

## Configuring a repository for CI

### Primary repository

To configure the primary repository, follow these steps:

1. Register with [WarpBuild](https://www.warpbuild.com/) and purchase runners.
2. Install the WarpBuild GitHub app against the GitHub organization.
3. Enable organisation-level runners to be used in public repositories:
   1. `Org settings -> Actions -> Runner Groups -> Default -> Allow public repos`
4. Permit the following actions to run:
   1. actions/cache/restore@\*
   1. actions/cache/save@\*
   1. actions/github-script@\*
   1. docker/setup-buildx-action@\*
   1. warpbuilds/cache/restore@\*
   1. warpbuilds/cache/save@\*

### Forked repositories

When used in a fork the CI will run on GitHub's free hosted runners by default.
In this case, GitHub's cache size limitations may cause caches to be frequently evicted and missed, but the workflows will run (slowly).

It is also possible to use your own WarpBuild Runners in your own fork with an appropriate patch to the `REPO_USE_WARP_RUNNERS` variable in ../.github/workflows/ci.yml
NB that WarpBuild Runners only work at an organisation level, therefore in order to use your own WarpBuild Runners, *the fork must be within your own organisation*.
