Previously on #homelab:
 |
Laminar is a much more opinionated application, mostly in the positive sense of that term, than Jenkins. If Jenkins (as its icon suggests) is an obsequious English butler or valet, then Laminar is the stereotype of the brusque New Yorker: forgot to mark your $JOB.init script as executable? “Hey pal. I’m walking here.”
But after struggling occasionally with the complexity and sometimes opacity of Jenkins (which SSH key is it using?) the simplicity and humility of Laminar comes as a relief. Run a sequence of commands? That’s what a shell is for; it’s not Laminar’s job; Laminar just runs a single script. Run a command on a timer? That’s what cron (or anacron) is for; it’s not Laminar’s job; Laminar provides a trigger command that you can add to your crontab.
So what does it provide? Mostly sequencing, monitoring, statistics-gathering, artifact-gathering, and a web UI. (Unlike Jenkins, the web UI is read-only – but as it exposes the contents of all packages built using it, it’s still best to keep it secure.) I have mine set up to, once a week, do a rustup update and then check that all my projects still build and pass their tests with the newest nightly build (and beta, and stable, and the oldest supported version). It’s very satisfying to glance at the Laminar page and be reassured that everything still builds and works, even if I’ve been occupied with other things that week. (And conversely, on the rare occasions when a new nightly breaks something, at least I find out about it early, as opposed to it suddenly being in my way at a time when I’m filled with the urge to be writing some new thing.)
This blog post will cover:
- Installing Laminar
- CI for Chorale, a C++ package
- CI for Cotton, a Rust package
- Setting up Git to build on push
- CI for rustup
You should probably skim at least the first part of the C++ section even if you’re mostly interested in Rust, as it introduces some basic Laminar concepts and techniques.
By the way, it’s reasonable to wonder whether, or why, self-hosted CI is even a thing, considering that Github Actions offer free CI for open-source projects (up to a certain, but very generous, usage limit). One perfectly adequate answer is that the hobby of #homelab is all about learning how things work – learning which doesn’t happen if someone else’s cloud service is already doing all the work. But there are other good answers too: eventually (but not in this blog post) I’m going to want CI to run tests on embedded systems, STM32s and RP2040s and the like – real physical hardware, which is attached to servers here but very much not attached to Github’s CI servers. (Emulation can cover some of this, but not for instance driver work, where the main source of bugs is probably misconceptions about how the actual hardware works.) Yet a third reason is trust: for a released open source project there’s, by definition, no point in keeping the source secret. But part of the idea of these blog posts is to document best practices which commercial organisations, too, might wish to adopt – and they might have very different opinions on uploading their secret sauce to third-party services, even ones sworn to secrecy by NDA. And even a project determined to make the end result open-source, won’t necessarily be making all their tentative early steps out in the open. Blame Apple, if you like, for that attitude; blame their habit of saying, “By the way, also, this unexpected thing. And you can buy it today!”
1. Installing Laminar
This is the part where it becomes clear that Laminar is quite a niche choice of CI engine. It is packaged for both Debian and Ubuntu, but there is a bug in both the Debian and Ubuntu packages – it’s not upstream, it’s in the Debian patchset – which basically results in nothing working. So you could either follow the suggestions in the upstream bug report of using a third-party Ubuntu PPA or the project’s own binary .deb releases, or you could do what I did and install the broken Ubuntu package anyway (to get the laminar user, the systemd scripts, etc. set up), then build Laminar 1.2 from upstream sources and install it over the top.
Either way, if you navigate to the Laminar web UI (on port 8080 of the server) and see even the word “Laminar” on the page, your installation is working and you’ve avoided the bug.
The default install sets the home directory for the laminar user to /var/lib/laminar; this is the Debian standard for system users, but to make things less weird for some of the tools I’m expecting Laminar to run (e.g., Cargo), I changed it (in /etc/passwd) to be /home/laminar.
2. CI for Chorale, a C++ package
I use Laminar to do homelab builds of Chorale, a C++ project comprising a UPnP media-server, plus some related bits and pieces. For the purposes of this blog post, it’s a fairly typical C++ program with a typical (and hopefully pretty sensible) Autotools-based build system.
Laminar is configured, in solid old-school Unix fashion, by a collection of text files and shell scripts. These all live (in the default configuration) under /var/lib/laminar/cfg, which you should probably chown -R to you and also check into a Git repository, to track changes and keep backups. (The installation process sets up a user laminar, which should remain a no-login user.)
All build jobs execute in a context, which allows sophisticated build setups involving multiple build machines and so on; for my purposes everything executes in a simple context called local:
| /var/lib/laminar/cfg/contexts/local.conf |
|---|
EXECUTORS=1 JOBS=* |
This specifies that only one build job can be run at a time (but it can be any job), overriding Laminar’s default context which allows for up to six executors: it’s just a Raspberry Pi, after all, we don’t want to overstress it.
2.1 C++: building a package
When it comes to the build directories for its build jobs, Laminar is much more disciplined (or, again, opinionated) than Jenkins: it keeps a rigid distinction between (a) the build directory itself, which is temporary, (b) a persistent directory shared between runs of the same job, the workspace, and (c) a persistent directory dedicated to each run, the archive. So the usual pattern is to keep the git checkout in the workspace (to save re-downloading the whole repo each time), then each run can do a git pull, make a copy of the sources into the build directory, do the build (leaving the workspace with a clean checkout), and finally store its built artifacts into the archive. All of which is fine except for the very first build, which needs to do the git clone. In Laminar this is dealt with by giving the job an init script (remember to mark it executable!):
| /var/lib/laminar/cfg/jobs/chorale.init |
|---|
#!/bin/bash -xe git clone /home/peter/git/chorale.git . |
as well as its normal run script (which also needs to be marked executable):
| /var/lib/laminar/cfg/jobs/chorale.run |
|---|
#!/bin/bash -xe
(
flock 200
cd $WORKSPACE/chorale
git pull --rebase
cd -
cp -al $WORKSPACE/chorale chorale
) 200>$WORKSPACE/lock
cd chorale
libtoolize -c
aclocal -I autotools
autoconf
autoheader
echo timestamp > stamp-h.in
./configure
make -j4 release
cp chorale*.tar.bz2 $ARCHIVE/
laminarc queue chorale-package |
There’s a few things going on here, so let’s break it down. The business with flock is a standard way, suggested in Laminar’s own documentation, of arranging that only one job at a time gets to execute the commands inside the parentheses – this isn’t necessarily likely to be an issue, as we’ve set EXECUTORS=1, but git would get in such a pickle if it happened that it’s a sensible precaution anyway. These protected commands update the repository from upstream (here, a git server on the same machine), then copy the sources into the build directory (via hard-linking, cp’s -l, to save time and space).
Once that’s done, we can proceed to do the actual build; the commands from libtoolize as far as make are the standard sequence for bootstrapping an Autotools-based C++ project from bare sources. (It’s not exactly Joel Test #2 compliant, mostly for Autotools reasons, although at least any subsequent builds from the same tree would be single-command.)
Chorale, as is standard for C++ packages, is released and distributed as a source tarball, which in this case is produced by the release target in the Makefile. The final cp command copies this tarball to the Laminar archive directory corresponding to this run of this job. (The archive directory will have a name like /var/lib/laminar/archive/chorale/33, where the “33” is a sequential build number.)
The final command, laminarc for “laminar client”, queues-up the next job in the chain, testing the contents of the Chorale package. (The bash -xe at the top, ensures that if the build process produces any errors, the script will terminate with an error and not get as far as kicking off the test job.)
That’s all that’s needed to set up a simple C++ build job – Laminar doesn’t have any concept of registering or enrolling a job; just the existence of the $JOB.run file is enough for the job to exist. To run it (remembering that the web UI is read-only), execute laminarc queue chorale and you should see the web UI spring into life as the job gets run. Of course, it will fail if any of the prerequisites (gcc, make, autoconf, etc.) are missing from the build machine; add them either manually (sudo apt-get install ...) or perhaps using Chef, Ansible or similar. Once the build succeeds (or fails) you can click around in the web UI to find the logs or perhaps download the finished tarball.
2.2 C++: running tests
The next job in the chain, chorale-package, tests that the packaging process was successful (and didn’t leave out any important files, for instance); it replicates what the user of Chorale would do after downloading a release. This time the run script gets the sources not from git, but from the package created by (the last successful run of) the chorale job, so no init script is needed:
| /var/lib/laminar/cfg/jobs/chorale-package.run |
|---|
#!/bin/bash -xe PACKAGE=/var/lib/laminar/archive/chorale/latest/chorale-*.tar.bz2 tar xf $PACKAGE cd chorale* ./configure make -j4 EXTRA_CCFLAGS=-Werror make -j4 EXTRA_CCFLAGS=-Werror check laminarc queue chorale-gcc12 chorale-clang |
Like a user of Chorale, the script just untars the package and expects configure and make to work. The build fails if that doesn’t happen. This job also runs Chorale’s unit-tests using make check. This time, we build with the C++ compiler’s -Werror option, to turn all compiler warnings into hard errors which will fail the build.
If everything passes, it’s clear that everything is fine when using the standard Ubuntu C++ compiler. The final two jobs, kicked-off whenever the chorale-package job succeeds, build with alternative compilers just to get a second opinion on the validity of the code (and to avoid unpleasant surprises when the standard compiler is upgraded in subsequent Ubuntu releases):
| /var/lib/laminar/cfg/jobs/chorale-gcc12.run |
|---|
#!/bin/bash -xe PACKAGE=/var/lib/laminar/archive/chorale/latest/chorale-*.tar.bz2 tar xf $PACKAGE GCC_FLAGS="-Werror" cd chorale* ./configure CC=gcc-12 CXX=g++-12 make -j4 CC=gcc-12 EXTRA_CCFLAGS="$GCC_FLAGS" make -j4 CC=gcc-12 EXTRA_CCFLAGS="$GCC_FLAGS" GCOV="gcov-12" check |
New compiler releases sometimes introduce new, useful warnings; this script is a good place to evaluate them before adding them to configure.ac. Similarly, the chorale-clang job checks that the sources compile with Clang, a compiler which has often found issues that G++ misses (and vice versa). Clang also has some useful extra features, the undefined-behaviour sanitiser and address sanitiser, which help to detect code which compiles but then can misbehave at runtime:
| /var/lib/laminar/cfg/jobs/chorale-clang.run |
|---|
#!/bin/bash -xe
PACKAGE=/var/lib/laminar/archive/chorale/latest/chorale-*.tar.bz2
tar xf $PACKAGE
cd chorale*
./configure CC=clang CXX=clang++
# -fsanitize=thread incompatible with gcov
# -fsanitize=memory needs special libc++
#
for SANE in undefined address ; do
CLANG_FLAGS="-Werror -fsanitize=$SANE -fno-sanitize-recover=all"
make -j4 CC=clang EXTRA_CCFLAGS="$CLANG_FLAGS"
make -j4 CC=clang EXTRA_CCFLAGS="$CLANG_FLAGS" GCOV="llvm-cov gcov" tests
make clean
done |
If the Chorale code passes all of these hurdles, then it’s probably about as ready-to-release as it’s possible to programmatically assess.
3. CI for Cotton, a Rust package
All the tools and dependencies required to build a typical C++ package are provided by Ubuntu packages and are system-wide. But Rust’s build system encourages the use of per-user toolchains and utilities (as well as per-project dependencies). So before we do anything else, we need to install Rust for the laminar user – i.e., as the laminar user – which requires a moment’s thought, as we carefully set up laminar to be a no-login user. So we can’t just su to laminar and run rustup-init normally; we have to use su to execute one command at a time from a normal user account.
So start by downloading the right rustup-init binary for your system – here, on a Raspberry Pi, that’s the aarch64-unknown-linux-gnu one. But then execute it (and then use it to download extra toolchains) as the laminar user (bearing in mind that rustup-init’s careful setup of the laminar user’s $PATH will not be in effect):
$ $ $ $ $ $ |
sudo -u laminar /home/peter/rustup-init sudo -u laminar /home/laminar/.cargo/bin/rustup toolchain install beta sudo -u laminar /home/laminar/.cargo/bin/rustup toolchain install nightly sudo -u laminar /home/laminar/.cargo/bin/rustup toolchain install 1.56 sudo -u laminar /home/laminar/.cargo/bin/rustup +nightly component add llvm-tools-preview sudo -u laminar /home/laminar/.cargo/bin/cargo install rustfilt |
The standard rustup-init installs the stable toolchain, so we just need to add beta, nightly, and 1.56 – that last chosen because it’s Cotton’s “minimum supported Rust version” (MSRV), which in turn was selected because it was the first version to support the 2021 Edition of Rust, and that seemed to be as far back as it was reasonable to go. We also install llvm-tools-preview and rustfilt, which we’ll be using for code-coverage later.
So to the $JOB.run scripts for Cotton. What I did here was notice that I’ve actually got a few different Rust packages to build, and they all need basically the same things doing to them. So I took advantage of the Laminar /var/lib/laminar/cfg/scripts directory, and made all the infrastructure common among all the Rust packages. When running a job, Laminar arranges that the scripts directory is on the shell’s $PATH (and note that it’s in the cfg directory, so will be captured and versioned if you set that up as a Git checkout). This means that, as far as Cotton is concerned – after an init script that’s really just like the C++ one:
| /var/lib/laminar/cfg/jobs/cotton.init |
|---|
#!/bin/bash -xe git clone /home/peter/git/cotton.git . |
– the other build scripts come in pairs: one that’s Cotton-specific but really just runs a shared script which is generic across projects, and then the generic one which does the actual work. We’ll look at the specific one first:
| /var/lib/laminar/cfg/jobs/cotton.run |
|---|
#!/bin/bash -xe
BRANCH=${BRANCH-main}
do-checkout cotton $BRANCH
export LAMINAR_REASON="built $BRANCH"
laminarc queue cotton-doc BRANCH=$BRANCH \
cotton-grcov BRANCH=$BRANCH \
cotton-1.56 BRANCH=$BRANCH \
cotton-beta BRANCH=$BRANCH \
cotton-nightly BRANCH=$BRANCH |
The assignment to BRANCH is a Bash-ism which means, “use the variable $BRANCH if it exists, but if it doesn’t exist, default to main”. This is usually what we want (in particular, a plain laminarc queue cotton will build main), but making it flexible will come in handy later when we build the Git push hook. All the actual building is done by the do-checkout script, and then on success (remembering that bash -xe means the script gets aborted on any failures) we go on to queue all the downstream jobs. Note that when parameterising jobs using laminarc’s VAR=VALUE facility, each VAR applies only to one job, not to all the jobs named.
The do-checkout script is very like the one for Chorale, including the flock arrangement to serialise the git operations, and differing only in that it takes the project and branch to build as command-line parameters – and of course includes the usual Rust build commands instead of the C++/Autotools ones. (This time we can take advantage of rustup-init’s (Cargo’s) $PATH setup, but only if we source the environment file directly.)
| /var/lib/laminar/cfg/scripts/do-checkout |
|---|
#!/bin/bash -xe
PROJECT=$1
BRANCH=$2
# WORKSPACE is predefined by Laminar itself
(
flock 200
cd $WORKSPACE/$PROJECT
git fetch
git checkout $BRANCH
git pull --rebase
cd -
cp -al $WORKSPACE/$PROJECT $PROJECT
) 200>$WORKSPACE/lock
source $HOME/.cargo/env
rustup default stable
cd $PROJECT
cargo build --all-targets
cargo test |
Notice that this job explicitly uses the stable toolchain, minimising the chance of version-to-version breakage. We also want to test on beta, nightly, and MSRV though, which is what three of those downstream jobs are for. Here I’ll just show the setup for nightly, because the other two are exactly analogous. Again there’s a pair of scripts; firstly, there’s the specific one:
| /var/lib/laminar/cfg/jobs/cotton-nightly.run |
|---|
#!/bin/bash -xe
exec do-buildtest cotton nightly ${BRANCH-main} |
Really not much to see there. All the work, as before, is done in the generic script, which is parameterised by project and toolchain:
| /var/lib/laminar/cfg/scripts/do-buildtest |
|---|
#!/bin/bash -xe
PROJECT=$1
RUST=$2
BRANCH=$3
SOURCE=/var/lib/laminar/run/$PROJECT/workspace
(
flock 200
cd $SOURCE/$PROJECT
git checkout $BRANCH
cd -
cp -al $SOURCE/$PROJECT $PROJECT
) 200>$SOURCE/lock
source $HOME/.cargo/env
rustup default $RUST
cd $PROJECT
cargo build --all-targets --offline
cargo test --offline |
Here we lock the workspace again, just to avoid any potential clashes with a half-finished git update, but we don’t of course do another git update – we want to build the same version of the code that we just built with stable. For similar reasons, we run Cargo in offline mode, just in case anyone published a newer version of a dependency since we last built.
That’s the cotton-beta, cotton-nightly, and cotton-1.56 downstream jobs dealt with. There are two more: cotton-doc and cotton-grcov, which deal with cargo doc and code coverage respectively. The documentation one is the more straightforward:
| /var/lib/laminar/cfg/jobs/cotton-doc.run |
|---|
#!/bin/bash -xe
exec do-doc cotton ${BRANCH-main} |
And even the generic script (parameterised by project) is quite simple:
| /var/lib/laminar/cfg/scripts/do-doc |
|---|
#!/bin/bash -xe
PROJECT=$1
BRANCH=$2
SOURCE=/var/lib/laminar/run/$PROJECT/workspace
(
flock 200
cd $SOURCE/$PROJECT
git checkout $BRANCH
cd -
cp -al $SOURCE/$PROJECT $PROJECT
) 200>$SOURCE/lock
source $HOME/.cargo/env
rustup default stable
cd $PROJECT
cargo doc --no-deps --offline
cp -a target/doc $ARCHIVE |
It much resembles the normal build, except for running cargo doc instead of a normal build. On completion, though, it copies the finished documentation into Laminar’s $ARCHIVE directory, which makes it accessible from Laminar’s web UI afterwards.
The code-coverage scripts are more involved, largely because I couldn’t initially get grcov to work, and ended up switching to using LLVM’s own coverage tools instead. (But the scripts still have “grcov” in the names.) Once more the per-project script is simple:
| /var/lib/laminar/cfg/jobs/cotton-grcov.run |
|---|
#!/bin/bash -xe
exec do-grcov cotton ${BRANCH-main} |
And the generic script does the bulk of it (I cribbed this recipe from the rustc book, q.v.; I didn’t come up with it all myself):
| /var/lib/laminar/cfg/scripts/do-grcov |
|---|
#!/bin/bash -xe
PROJECT=$1
BRANCH=$2
SOURCE=/var/lib/laminar/run/$PROJECT/workspace
(
flock 200
cd $SOURCE/$PROJECT
git checkout $BRANCH
cd -
cp -al $SOURCE/$PROJECT $PROJECT
) 200>$SOURCE/lock
source $HOME/.cargo/env
rustup default nightly
cd $PROJECT
export RUSTFLAGS="-Cinstrument-coverage"
export LLVM_PROFILE_FILE="$PROJECT-%p-%m.profraw"
cargo test --offline --lib
rustup run nightly llvm-profdata merge -sparse `find . -name '*.profraw'` -o cotton.profdata
rustup run nightly llvm-cov show \
$( \
for file in \
$( \
cargo test --offline --lib --no-run --message-format=json \
| jq -r "select(.profile.test == true) | .filenames[]" \
| grep -v dSYM - \
); \
do \
printf "%s %s " -object $file; \
done \
) \
--instr-profile=cotton.profdata --format=html --output-dir=$ARCHIVE \
--show-line-counts-or-regions --ignore-filename-regex='/.cargo/' \
--ignore-filename-regex='rustc/' |
Honestly? Bit of a mouthful. But it does the job. Notice that the output directory is set to Laminar’s $ARCHIVE directory so that, again, the results are viewable through Laminar’s web UI. (Rust profiling doesn’t produce branch coverage as such, but “Region coverage” – which counts what a compiler would call basic blocks – amounts to much the same thing in practice.) The results will look a bit like this:
Why yes, that is very good coverage, thank you for noticing!
4. Setting up Git to build on push
So far in our CI journey, we have plenty of integration, but it’s not very continuous. What’s needed is for all this mechanism to swing into action every time new code is pushed to the (on-prem) Git repositories for Chorale or Cotton.
Fortunately, this is quite straightforward – or, at least, good inspiration is available online. Pushes to the Git repository for Cotton can be hooked by adding a script as hooks/post-receive under the Git server’s cotton.git directory (the hooks directory is probably already there). In one of those Git features that at first makes you think, “this is a bit over-engineered”, but then makes you realise, “wait, this couldn’t actually be made any simpler while still working in full generality”, the Git server passes to this script, on its standard input, a line for every Git “ref” being pushed – for these purposes, refs are mostly branches – along with the Git revisions at the old tip and new tip of the branch.
Laminar comes with an example hook which builds every commit on every branch pushed. I admire this but don’t follow it; it’s great for preserving bisectability, but seems like it would lead to a lot of interactive rebasing every time a feature branch is rebased on a later main – not to mention a lot of building by the CI server. So the hook I actually use just builds the tip of each branch:
| git/cotton.git/hooks/post-receive |
|---|
#!/bin/bash -ex
while read oldrev newrev ref
do
if [ "${ref:0:11}" == "refs/heads/" ];
then
export BRANCH=${ref:11}
export LAMINAR_REASON="git push $BRANCH"
laminarc queue cotton BRANCH=$BRANCH
fi
done |
The LAMINAR_REASON appears in the web UI and indicates which branch each run is building:
5. CI for rustup
The final piece of the puzzle, at least for today, is the continuous integration of Rust itself. As new nightlies, and betas, and even stable toolchains come out, I’d like it to be a computer’s job, not that of a person, to rebuild everything with the new version. (Especially if that person would be me.)
This too, however, is straightforward with all the infrastructure put in place by the rest of this blog post. All that’s needed is a new job file which runs rustup-update:
| /var/lib/laminar/cfg/jobs/rustup-update.run |
|---|
#!/bin/bash -ex export LAMINAR_REASON="rustup update" source $HOME/.cargo/env rustup update laminarc queue cotton assay sparkle |
The rustup update command updates all the toolchains; once that is done, the script queues-up builds of all the Rust packages I build. I schedule a weekly build in the small hours of Thursday morning, using cron:
| edit crontab using “crontab -e” |
|---|
0 3 * * 4 LAMINAR_REASON="Weekly rustup" laminarc queue rustup-update |
With a bit of luck, this means that by the time I sit down at my desk on Thursday morning, all the jobs have run and Laminar is showing a clean bill of health. As I’ve been playing with Rust for quite a long elapsed time, but really only taking it seriously in quite occasional bursts of energy, having everything kept up-to-date automatically during periods when I’m distracted by a different shiny thing is a real pleasure.
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