Laminar CI

Laminar is a lightweight and modular Continuous Integration service for Linux. It is self-hosted and developer-friendly, eschewing a configuration web UI in favor of simple version-controllable configuration files and scripts.

Laminar encourages the use of existing GNU/Linux tools such as bash and cron instead of reinventing them.

Although the status and progress front-end is very user-friendly, administering a Laminar instance requires writing shell scripts and manually editing configuration files. That being said, there is nothing esoteric here and the tutorial below should be straightforward for anyone with even very basic Linux server administration experience.

Getting Started

Building from source

First install development packages for capnproto (git), rapidjson, websocketpp, sqlite and boost-filesystem from your distribution's repository or other source. Then:

git clone https://github.com/ohwgiles/laminar.git
cd laminar
cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/
make -j4
sudo make install

make install includes a systemd unit file. If you intend to use it, consider creating a new user laminar or modifying the user specified in the unit file.

Installation from binaries

Alternatively to the source-based approach shown above, precompiled packages are supplied for x86_64 Debian Stable and CentOS 7.

Under Debian:

wget https://github.com/ohwgiles/laminar/releases/download/0.4/laminar-0.4-1-amd64.deb
sudo dpkg -i laminar-0.4-1-amd64.deb

Under CentOS:

wget https://github.com/ohwgiles/laminar/releases/download/0.4/laminar-0.4-1.x86_64.rpm
sudo rpm -i laminar-0.4-1.x86_64.rpm

Both install packages will create a new laminar user and install (but not activate) a systemd service for launching the laminar daemon.

Service Configuration

Use systemctl start laminar to start the laminar system service and systemctl enable laminar to launch it automatically on system boot.

After starting the service, an empty laminar dashboard should be available at http://localhost:8080

Laminar's configuration file may be found at /etc/laminar.conf. Laminar will start with reasonable defaults if no configuration can be found.

Running on a different HTTP port or Unix socket

Edit /etc/laminar.conf and change LAMINAR_BIND_HTTP to IPADDR:PORT, unix:PATH/TO/SOCKET or unix-abstract:SOCKETNAME. IPADDR may be * to bind on all interfaces. The default is *:8080.

Do not attempt to run laminar on port 80. This requires running as root, and Laminar will not drop privileges when executing job scripts! For a more complete integrated solution (including SSL), simply run laminar as a reverse proxy behind a regular webserver.

Running behind a reverse proxy

Laminar relies on WebSockets to provide a responsive, auto-updating display without polling. This may require extra support from your frontend webserver.

For nginx, see NGINX Reverse Proxy and WebSocket proxying.

For Apache, see Apache Reverse Proxy and mod_proxy_wstunnel.

Set the page title

Change LAMINAR_TITLE in /etc/laminar.conf to your preferred page title.

More configuration options

See the reference section

User Guide

Terminology

• job: a task, identified by a name, comprising of one or more executable scripts.
• run: a numbered execution of a job

Throughout this document, the fixed path /var/lib/laminar is used. This is simply a default value and can be changed by setting LAMINAR_HOME in /etc/laminar.conf as desired.

Creating a job

To create a job that downloads and compiles GNU Hello, create the file /var/lib/laminar/cfg/jobs/hello.run with the following content:

#!/bin/bash -ex
wget ftp://ftp.gnu.org/gnu/hello/hello-2.10.tar.gz
tar xzf hello-2.10.tar.gz
cd hello-2.10
./configure
make

Laminar uses your script's exit code to determine whether to mark the run as successful or failed. If your script is written in bash, the -e option is helpful for this. See also Exit and Exit Status.

Don't forget to mark the script executable:

chmod +x /var/lib/laminar/cfg/hello.run

Triggering a run

To trigger a run of the hello job, execute

laminarc trigger hello

This causes the /var/lib/laminar/cfg/hello.run script to be executed, with a working directory of /var/lib/laminar/run/hello/1

The result and log output should be visible in the Web UI at http://localhost:8080/jobs/hello/1

Isn't there a "Build Now" button I can click?

This is against the design principles of Laminar and was deliberately excluded. Laminar's web UI is strictly read-only, making it simple to deploy in mixed-permission or public environments without an authentication layer. Furthermore, Laminar tries to encourage ideal continuous integration, where manual triggering is an anti-pattern. Want to make a release? Push a git tag and implement a post-receive hook. Want to re-run a build due to sporadic failure/flaky tests? Fix the tests locally and push a patch. Experience shows that a manual trigger such as a "Build Now" button is often used as a crutch to avoid doing the correct thing, negatively impacting traceability and quality.

Triggering a job at a certain time

This is what cron is for. To trigger a build of hello every day at 0300, add

0 3 * * * LAMINAR_REASON="Nightly build" laminarc trigger hello

to laminar's crontab. For more information about cron, see man crontab.

LAMINAR_REASON is an optional human-readable string that will be displayed in the web UI as the cause of the build.

Triggering on a git commit

This is what git hooks are for. To create a hook that triggers the example-build job when a push is made to the example repository, create the file hooks/post-receive in the example.git bare repository.

#!/bin/bash
LAMINAR_REASON="Push to git repository" laminarc trigger example-build

What if your git server is not the same machine as the laminar instance?

Triggering on a remote laminar instance

laminarc and laminard communicate by default over an abstract unix socket. This means that any user on the same machine can send commands to the laminar service.

On a trusted network, you might want laminard to listen for commands on a TCP port instead. To achieve this, in /etc/laminar.conf, set

LAMINAR_BIND_RPC=*:9997

or any interface/port combination you like. This option uses the same syntax as LAMINAR_BIND_HTTP.

Then, point laminarc to the new location using an environment variable:

LAMINAR_HOST=192.168.1.1:9997 laminarc trigger example

Access control

If you need more flexibility, consider running the communication channel as a regular unix socket and applying user and group permissions to the file. To achieve this, set

LAMINAR_BIND_RPC=unix:/var/run/laminar.sock

or similar path in /etc/laminar.conf.

This can be securely and flexibly combined with remote triggering using ssh. There is no need to allow the client full shell access to the server machine, the ssh server can restrict certain users to certain commands (in this case laminarc). See the authorized_keys section of the sshd man page for further information.

Job chains

A typical pipeline may involve several steps, such as build, test and deploy. Depending on the project, these may be broken up into seperate laminar jobs for maximal flexibility.

The preferred way to accomplish this in Laminar is to use the same method as regular run triggering, that is, calling laminarc directly in your example.run scripts.

In addition to laminarc trigger, laminar start triggers a job run, but waits for its completion and returns a non-zero exit code if the run failed. Furthermore, both trigger and start will accept multiple jobs in a single invocation:

#!/bin/bash -xe

# simultaneously starts example-test-qemu and example-test-target
# and returns a non-zero error code if either of them fail
laminarc start example-test-qemu example-test-target

An advantage to using this laminarc approach from bash or other scripting language is that it enables highly dynamic pipelines, since you can execute commands like

if [ ... ]; then
  laminarc start example-downstream-special
else
  laminarc start example-downstream-regular
fi

laminarc start example-test-$TARGET_PLATFORM

laminarc reads the $JOB and $RUN variables set by laminard and passes them as part of the trigger/start request so the dependency chain can always be traced back.

Parameterized runs

Any argument passed to laminarc of the form var=value will be exposed as an environment variable in the corresponding build scripts. For example:

laminarc trigger example foo=bar

In /var/lib/laminar/cfg/jobs/example.run:

#!/bin/bash
if [ "$foo" == "bar" ]; then
   ...
else
   ...
fi

Pre-build actions

If the script /var/lib/laminar/cfg/jobs/example.before exists, it will be executed as part of the example job, before the primary /var/lib/laminar/cfg/jobs/example.run script.

See also script execution order

Passing variables between run scripts

Any script can set environment variables that will stay exposed for subsequent scripts of the same run using laminarc set. In example.before:

#!/bin/bash
laminarc set foo=bar

Then in example.run

#!/bin/bash
echo $foo            # prints "bar"

This works because laminarc reads $JOB and $NUM and passes them to the laminar daemon as part of the set request. (It is thus possible to set environment variables on other jobs by overriding these variables, but this is not very useful).

Post-build actions

Analagously to Pre-build actions, if the script example.after exists, it will be executed after the primary example.run script.

The $RESULT environment variable will contain the run result. See also Environment variables.

Archiving artefacts

Laminar's default behaviour is to remove the run directory /var/lib/laminar/run/JOB/RUN after its completion. This prevents the typical CI disk usage explosion and encourages the user to judiciously select artefacts for archive.

Laminar provides an archive directory /var/lib/laminar/archive/JOB/RUN and exposes its path in $ARCHIVE. example-build.after might look like this:

#!/bin/bash -xe
cp example.out $ARCHIVE/

This folder structure has been chosen to make it easy for system administrators to host the archive on a separate partition or network drive.

Conditionally trigger a downstream job

Often, you may wish to only trigger the example-test job if the example-build job completed successfully. example-build.after might look like this:

#!/bin/bash -xe
if [ "$RESULT" == "success" ]; then
  laminarc trigger example-test
fi

Accessing artifacts from an upstream build

Rather than implementing a separate mechanism for this, the path of the upstream's archive should be passed to the downstream run as a parameter. See Parameterized runs.

Email and IM Notifications

As well as per-job .after scripts, a common use case is to send a notification for every job completion. If the global after script at /var/lib/laminar/cfg/after exists, it will be executed after every job. One way to use this might be:

#!/bin/bash -xe
if [ "$RESULT" != "$LAST_RESULT" ]; then
  sendmail -t <<EOF
To: engineering@company.com
Subject: Laminar $JOB #$RUN: $RESULT
From: laminar-ci@company.com

Laminar $JOB #$RUN: $RESULT
EOF
fi

Of course, you can make this as pretty as you like. A helper script can be a good choice here.

If you want to send to different addresses dependending on the job, replace engineering@company.com above with a variable, e.g. $RECIPIENTS, and set RECIPIENTS=nora@company.com,joe@company.com in /var/lib/laminar/cfg/jobs/JOB.env. See Environment variables.

You could also update the $RECIPIENTS variable dynamically based on the build itself. For example, if your run script accepts a parameter $rev which is a git commit id, as part of your job's .after script you could do the following:

author_email=$(git show -s --format='%ae' $rev)
laminarc set RECIPIENTS $author_email

Helper scripts

The directory /var/lib/laminar/cfg/scripts is automatically prepended to the PATH of all runs. It is a convenient place to drop executables or scripts to help keep individual job scripts clean and concise. A simple example might be /var/lib/laminar/cfg/scripts/success_trigger:

#!/bin/bash -e
if [ "$RESULT" == "success" ]; then
  laminarc trigger "$@"
fi

With this in place, any .after script can conditionally trigger a downstream job more succinctly:

success_trigger example-test

Another excellent candidate for helper scripts is automatically sending notifications on job status change. See Example scripts for more useful starting points.

Data sharing and Workspaces

Often, a job will require a (relatively) large block of (relatively) unchanging data. Examples are a git repository with a long history, or static asset files. Instead of fetching everything from scratch for every run, a job may make use a workspace, a per-job folder that is reused between builds.

For example, the following script creates a tarball containing both compiled output and some static asset files from the workspace:

#!/bin/bash -ex
git clone /path/to/sources .
make
# Use a hardlink so the arguments to tar will be relative to the CWD
ln $WORKSPACE/StaticAsset.bin ./
tar zc a.out StaticAsset.bin > MyProject.tar.gz
# Archive the artifact (consider moving this to the .after script)
mv MyProject.tar.gz $ARCHIVE/

For a project with a large git history, it can be more efficient to store the sources in the workspace:

#!/bin/bash -ex
cd $WORKSPACE/myproject
git pull
cd -

cmake $WORKSPACE/myproject
make -j4

CAUTION: By default, laminar permits multiple simultaneous runs of the same job. If a job can modify the workspace, this might result in inconsistent builds when the job has multiple simultaneous runs. This is unlikely to be an issue for nightly builds, but for SCM-triggered builds it will be. To solve this, use nodes to restrict simultaneous execution of jobs, or locks to temporarily take exclusive control of a resource.

Laminar will automatically create the workspace for a job if it doesn't exist when a job is executed. In this case, the /var/lib/laminar/cfg/jobs/JOBNAME.init will be executed if it exists. This is an excellent place to prepare the workspace to a state where subsequent builds can rely on its content.

Nodes and Tags

In Laminar, a node is an abstract concept allowing more fine-grained control over job execution scheduling. Each node can be defined to support an integer number of executors, which defines how many runs can be executed simultaneously.

A typical example would be to allow only a few concurrent CPU-intensive jobs (such as compilation), while simultaneously allowing many more less-intensive jobs (such as monitoring or remote jobs). To create a node named build with 3 executors, create the file /var/lib/laminar/cfg/nodes/build.conf with the following content:

EXECUTORS=3

To associate jobs with nodes, laminar uses tags. Tags may be applied to nodes and jobs. If a node has tags, only jobs with a matching tag will be executed on it. If a node has no tags, it will accept any job. To tag a node, add them to /var/lib/laminar/cfg/nodes/NODENAME.conf:

EXECUTORS=3
TAGS=tag1,tag2

To add a tag to a job, add the following to /var/lib/laminar/cfg/jobs/JOBNAME.conf:

TAGS=tag2

If Laminar cannot find any node configuration, it will assume a single node with 6 executors and no tags.

Grouping jobs with tags

Tags are also used to group jobs in the web UI. Each tag will presented as a tab in the "Jobs" page.

Node scripts

If /var/lib/laminar/cfg/nodes/NODENAME.before exists, it will be executed before the run script of a job scheduled to that node. Similarly, if /var/lib/laminar/cfg/nodes/NODENAME.after exists, it will be executed after the run script of a job scheduled to that node.

Node environment

If /var/lib/laminar/cfg/nodes/NODENAME.env exists and can be parsed as a list of KEY=VALUE pairs, these variables will be exposed as part of the run's environment.

Remote jobs

Laminar provides no specific support, bash, ssh and possibly NFS are all you need. For example, consider two identical target devices on which test jobs can be run in parallel. You might create a node for each, /var/lib/laminar/cfg/nodes/target{1,2}.conf with a common tag:

EXECUTORS=1
TAGS=remote-target

In each node's .env file, set the individual device's IP address:

TARGET_IP=192.168.0.123

And tag the job accordingly in /var/lib/laminar/cfg/jobs/myproject-test.conf:

TAGS=remote-target

This means the job script /var/lib/laminar/cfg/jobs/myproject-test.run can be generic:

#!/bin/bash -e

ssh root@$TARGET_IP /bin/bash -xe <<"EOF"
  uname -a
  ...
EOF
scp root@$TARGET_IP:result.xml "$ARCHIVE/"

Don't forget to add the laminar user's public ssh key to the remote's authorized_keys.

Docker container jobs

Laminar provides no specific support, but just like remote jobs these are easily implementable in plain bash:

#!/bin/bash

docker run --rm -ti -v $PWD:/root ubuntu /bin/bash -xe <<EOF
  git clone http://...
  ...
EOF

Locks

Locks are a simple way to control access to shared resources. Any string may be used as a lock name. The command laminarc lock mylock locks mylock. Subsequent calls to laminarc lock mylock will block until laminarc release mylock is called a corresponding number of times.

CAUTION: Locks are independent of any other job control mechanism in laminar, and will not be released automatically. Making sure calls to lock and release are symmetric is the administrator's responsibility.

An example use builds on the situation described in Data sharing and Workspaces, where a large git repository is stored in the workspace. Conisder this run script:

#!/bin/bash -x

# This script expects to be passed the parameter `rev` which
# should refer to a specific git commit in its source repository.
# The commit ids could have been read from a server-side
# post-commit git hook, where many commits could have been pushed
# at once, but we want to check them all individually. This means
# this job can be executed several times (with different commit ids)
# at once.

cd $WORKSPACE
# Acquire a lock for modifying the workspace
laminarc lock $JOB-workspace
# Download all the latest commits
git fetch
git checkout $rev
cd -
# Fast copy (hard-link) the specific checkout to the build dir
cp -al $WORKSPACE/src src
# Release the lock to allow other jobs to do the same
laminarc release $JOB-workspace

# run the (much longer) build process
set -e
cmake src
make

Reference

Server options

laminard reads the following variables from the environment, which are expected to be sourced by systemd from /etc/laminar.conf:

• LAMINAR_HOME: The directory in which laminard should find job configuration and create run directories. Default /var/lib/laminar
• LAMINAR_BIND_HTTP: The interface/port or unix socket on which laminard should listen for incoming connections to the web frontend. Default *:8080
• LAMINAR_BIND_RPC: The interface/port or unix socket on which laminard should listen for incoming commands such as build triggers. Default unix-abstract:laminar
• LAMINAR_TITLE: The page title to show in the web frontend.
• LAMINAR_KEEP_RUNDIR: If set, do not delete run directories after completion
• LAMINAR_ARCHIVE_URL: If set, the web frontend served by laminard will use this URL to form links to artefacts archived jobs. Must be synchronized with web server configuration.

Script execution order

When $JOB is triggered on $NODE, the following scripts (relative to $LAMINAR_HOME/cfg) may be triggered:

• jobs/$JOB.init if the workspace did not exist
• before
• nodes/$NODE.before
• jobs/$JOB.before
• jobs/$JOB.run
• jobs/$JOB.after
• nodes/$NODE.after
• after

Environment variables

The following variables are available in run scripts:

• RUN integer number of this run
• JOB string name of this job
• RESULT string run status: "success", "failed", etc.
• LAST_RESULT string previous run status
• WORKSPACE path to this job's workspace
• ARCHIVE path to this run's archive

In addition, $LAMINAR_HOME/cfg/scripts is prepended to $PATH. See helper scripts.

Laminar will also export variables in the form KEY=VALUE found in these files:

• env
• nodes/$NODE.env
• jobs/$JOB.env

Finally, variables supplied on the command-line call to laminarc start or laminarc trigger will be available. See parameterized builds

laminarc

laminarc commands are:

• trigger [JOB [PARAMS...]]... triggers one or more jobs with optional parameters, returning immediately.
• start [JOB [PARAMS...]]... triggers one or more jobs with optional parameters and waits for the completion of all jobs. Returns a non-zero error code if any job failed.
• set [VARIABLE=VALUE]... sets one or more variables to be exported in subsequent scripts for the run identified by the $JOB and $RUN environment variables
• lock [NAME] acquires the lock named NAME
• release [NAME] releases the lock named NAME

laminarc connects to laminard using the address supplied by the LAMINAR_HOST environment variable. If it is not set, laminarc will first attempt to use LAMINAR_BIND_RPC, which will be available if laminarc is executed from a script within laminard. If neither LAMINAR_HOST nor LAMINAR_BIND_RPC is set, laminarc will assume a default host of unix-abstract:laminar.

Appendix: Example scripts