In April 2018 we started to experiment more seriously with GitLab and GitLab CI.

GitLab CI

Support for GitLab CI was added in https://trac.sagemath.org/ticket/24655.

Free Runners with Google Compute Engine

Currently, Google gives everybody who signs up $300 of credit for 12 months. They won't charge you unless you explicitly upgrade, and there are a few limitations (e.g, at most 8 CPUs per regions.) Btw., they don't charge you if you upgrade unless you run out of the free credit.

1. Sign up at cloud.google.com (you might want to use an account that you don't use for anything else on cloud.google.com, so your quotas do not interfere with what we are doing here…)
2. Go to "Compute Engine" → "VM Instance" → "Create Instance".
   • Name, e.g., "gitlabci-orchestrator"
   • Zone "us-east1-b"
   • Machine Type "micro"
   • Boot Disk "Debian Stretch"
   • Select "Allow full access to all Cloud APIs"
   • Keep Defaults for everything else, and click "Create"
3. Wait for your machine to boot and click the "SSH" button to connect.

   * sudo su
   * apt-get update
   * apt-get install -y apt-transport-https ca-certificates curl gnupg2 software-properties-common
   * curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
   * add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"
   * curl -L https://packages.gitlab.com/install/repositories/runner/gitlab-runner/script.deb.sh | bash
   * cat > /etc/apt/preferences.d/pin-gitlab-runner.pref <<EOF
Explanation: Prefer GitLab provided packages over the Debian native ones
Package: gitlab-runner
Pin: origin packages.gitlab.com
Pin-Priority: 1001
EOF
   * apt-get update
   * apt-get install -y gitlab-runner docker-ce
   * base=https://github.com/docker/machine/releases/download/v0.14.0
   * curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/tmp/docker-machine
   * install /tmp/docker-machine /usr/local/bin/docker-machine
   * REGIONS="us-east4-c us-central1-c us-west1-c europe-west4-c europe-west1-c europe-west2-c europe-west3-c asia-east1-c asia-southeast1-a australia-southeast1-c asia-south1-c" # for a maximum of 11*2+1 < 24 CPUs, the free tier limit
   * export REGISTRATION_TOKEN=mTtHSpYUitgJFjsSuzXL
   * NAME=gce-jrueth # a *short* name that contains gce and your username (and only lowercase characters and hyphens)
   * export REGISTER_LOCKED=false
   * PROJECT=tidy-scholar-202621 # the name of the google cloud project (click on "My First Project" to find out)
   * for region in $REGIONS;do gitlab-runner register --tag-list big,long,standard-2 --run-untagged --name $NAME-$region --limit 1 --executor docker+machine --env "DOCKER_DRIVER=overlay2" --docker-privileged --url https://gitlab.com --non-interactive --docker-image docker:latest --docker-volumes "/var/run/docker.sock:/var/run/docker.sock" --docker-volumes "/dev/urandom:/dev/random" --docker-shm-size 2147483648 --machine-machine-driver google --machine-idle-time 600 --machine-machine-name "$NAME-%s" --machine-machine-options "google-project=$PROJECT" --machine-machine-options "google-machine-type=n1-standard-2" --machine-machine-options "google-machine-image=https://www.googleapis.com/compute/v1/projects/ubuntu-os-cloud/global/images/family/ubuntu-1804-lts" --machine-machine-options "google-tags=gitlab-ci-slave" --machine-machine-options "google-preemptible=false" --machine-machine-options "google-zone=$region" --machine-machine-options "google-use-internal-ip=true" --machine-machine-options "google-disk-type=pd-standard" --machine-machine-options "google-disk-size=64"; done
   * vim /etc/gitlab-runner/config.toml
   * replace concurrent=1 with concurrent=11
   * systemctl restart gitlab-runner
   * exit
   * exit

Finally, have somebody with Owner access on the gitlab.com/sage group check that your runners are enabled and working.

TODO: There is some room for improvement here. These instances do not support caches (we do not use caching currently) and they always pull the sagemath-dev images from the registry which incurs quite a bit of ingress cost.