If you want to have a cost-effective and scalable solution for your CI/CD, it can be useful to use Gitlab Runner with its autoscaling feature. In this example, we'll configure Gitlab Runner in AWS that will serve as the bastion host with docker-machine spawning spot instances. Also there is ECR authentication stage (in this case we can pull our images from ECR).

We will use such tools as:

• Gitlab Runner
• Amazon’s EC2 Spot Instances
• Docker Machine

The first step is to install GitLab Runner in an EC2 instance that will serve as the bastion that spawns new machines. This doesn’t have to be a powerful machine since it will not run any jobs itself, but a t2.micro instance will do. This machine will be a dedicated host since we need it always up and running, thus it will be the only standard cost.

Security Group for Bastion host must contain ingress rule for 2376 port

To create EC2 instance (Ubuntu HVM) with all depencies installed - paste this into User Data

#!/bin/bash
sudo apt-get update
sudo apt-get upgrade

#installing docker depencies
sudo apt-get install -y apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"
sudo apt-get update

#installing docker with user rights
sudo apt-get install -y docker-ce
sudo usermod -aG docker ubuntu

#installing awsutils with Go laguage
sudo apt-get install awscli
sudo apt-get install golang-go

#export Go $PATH
export GOPATH=$HOME/go
export PATH=$PATH:$GOPATH/bin

#installing docker-compose + machine
curl -L https://github.com/docker/compose/releases/download/1.21.0/docker-compose-$(uname -s)-$(uname -m) -o /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
base=https://github.com/docker/machine/releases/download/v0.16.0 &&
  curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/tmp/docker-machine &&
  sudo mv /tmp/docker-machine /usr/local/bin/docker-machine &&
  chmod +x /usr/local/bin/docker-machine

#installing gitlab-runner
curl -L https://packages.gitlab.com/install/repositories/runner/gitlab-runner/script.deb.sh | sudo bash
sudo apt-get install gitlab-runner

Now go to your bastion host and run sudo gitlab-runner register

This command will generate example config.toml file with token we needed for our runner.

Then run sudo vim /etc/gitlab-runner/config.toml and copy generated token to buffer. Then paste it into your new config which is given below.

concurrent = 10
check_interval = 0

[[runners]]
  name = "%PROJECT_NAME% Runner"
  limit = 3
  url = "https://gitlab.codica.com/"
  token = "__TOKEN FROM PREVIOUS config.toml__"
  executor = "docker+machine"
  [runners.docker]
    tls_verify = false
    image = "alpine"
    privileged = true
    disable_cache = true
    volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
    shm_size = 0
  [runners.cache]
    Type = "s3"
    Path = "cache"
    [runners.cache.s3]
      ServerAddress = "s3.amazonaws.com"
      AccessKey = "XXXXXXXXX"
      SecretKey = "XXXXXXXXX"
      BucketName = "XXXXXXXXX"
      BucketLocation = "eu-central-1"
  [runners.machine]
    IdleCount = 2
    IdleTime = 300
    MaxBuilds = 10
    MachineDriver = "amazonec2"
    MachineName = "gitlab-docker-machine-%s"
    MachineOptions = ["amazonec2-access-key=XXXXXXXXX", "amazonec2-secret-key=XXXXXXXXX", "amazonec2-region=eu-central-1", "amazonec2-vpc-id=XXXXXXXXX", "amazonec2-subnet-id=XXXXXXXXX", "amazonec2-zone=%bastion host zone%", "amazonec2-tags=runner-manager-name,gitlab-aws-autoscaler,gitlab,true,gitlab-runner-autoscale,true", "amazonec2-security-group=%Your SG name%", "amazonec2-instance-type=t3.medium", "amazonec2-request-spot-instance=true", "amazonec2-spot-price=0.05"]
    OffPeakPeriods = ["* * 0-8,22-23 * * mon-fri *", "* * * * * sat,sun *"]
    OffPeakTimezone = "Europe/Kiev"
    OffPeakIdleCount = 0
    OffPeakIdleTime = 1200

Make sure you are under root user: sudo su

The next step is to configure your AWS account: aws configure

Then type: crontab -e and paste next string to the end of crontab:

0 */6 * * * RESULT=$(aws ecr get-login --no-include-email --region eu-central-1) && $RESULT >/dev/null 2>&1

By default ECR Credential Helper is used for ECR authorization. Here you can find detailed instructions for authorization in ECR.

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