User-data script to bootstrap self-hosted runner on ASG (#4)

This runner-supervisor script has been manually uploaded to S3 (it was too big
to include in the userdata)

The cloud init script has been manually uploaded by running, and the ASG
is configured to pick the Latest version already, so new instances will
start using the new script.

```
aws --profile airflow ec2 create-launch-template-version \
    --launch-template-name GithubRunner \
    --launch-template-data UserData="$(base64 -w0 cloud-init.yml)" \
    --source-version='$Latest'
```

.gitignore

@@ -0,0 +1,2 @@
+.cache
+__pycache__/

cloud-init.yml

@@ -0,0 +1,290 @@
+#cloud-config
+# 2021-02-19 21:48
+
+mounts:
+  - [tmpfs, /tmp, tmpfs, "defaults,noatime,size=10%"]
+  - [tmpfs, /var/lib/docker, tmpfs, "defaults,noatime,size=66%"]
+  - [tmpfs, /home/runner/actions-runner/_work, tmpfs, "defaults,noatime"]
+
+users:
+  - default
+  - name: runner
+
+packages:
+  - awscli
+  - build-essential
+  - docker.io
+  - git
+  - iptables-persistent
+  - jq
+  - python3-dev
+  - python3-venv
+  - python3-wheel
+  - yarn
+  - vector
+
+runcmd:
+  -
+    - bash
+    - -c
+    # https://github.com/actions/virtual-environments/blob/525f79f479cca77aef4e0a680548b65534c64a18/images/linux/scripts/installers/docker-compose.sh
+    - |
+      URL=$(curl -s https://api.github.com/repos/docker/compose/releases/latest | jq -r '.assets[].browser_download_url | select(endswith("docker-compose-Linux-x86_64"))')
+      curl -L $URL -o /usr/local/bin/docker-compose
+      chmod +x /usr/local/bin/docker-compose
+  -
+    - bash
+    - -c
+    - |
+      set -exu -o pipefail
+      echo "AWS_DEFAULT_REGION=$(cloud-init query region)" >> /etc/environment
+      set -a
+      . /etc/environment
+      set +a
+      echo "ASG_GROUP_NAME=$(aws ec2 describe-tags --filter Name=resource-id,Values=$(cloud-init query instance_id) Name=key,Values=aws:autoscaling:groupName \
+            | jq -r '@sh "\(.Tags[0].Value)"')" >> /etc/environment
+  - [systemctl, daemon-reload]
+  -
+    - bash
+    - -c
+    - |
+      python3 -mvenv /opt/runner-supervisor
+      /opt/runner-supervisor/bin/pip install -U pip python-dynamodb-lock-whatnick==0.9.3 click==7.1.2 psutil 'tenacity~=6.0'
+  -
+    - bash
+    - -c
+    - |
+      set -exu -o pipefail
+
+      usermod -G docker -a runner
+
+      mkdir -p ~runner/actions-runner
+      find ~runner -exec  chown runner: {} +
+      cd ~runner/actions-runner
+
+      RUNNER_VERSION="$0"
+
+      curl -L "https://github.com/ashb/runner/releases/download/v${RUNNER_VERSION}/actions-runner-linux-x64-${RUNNER_VERSION}.tar.gz" | tar -zx
+
+      set -a
+      . /etc/environment
+      set +a
+
+      aws s3 cp s3://airflow-ci-assets/runner-supervisor.py /opt/runner-supervisor/bin/runner-supervisor
+      chmod 755 /opt/runner-supervisor/bin/runner-supervisor
+
+      # Log in to a paid docker user to get unlimited docker pulls
+      aws ssm get-parameter --with-decryption --name /runners/apache/airflow/dockerPassword | \
+        jq .Parameter.Value -r | \
+        sudo -u runner docker login --username airflowcirunners --password-stdin
+    - 2.277.1-airflow1
+  - [systemctl, enable, --now, iptables.service]
+  # Restart docker after applying the user firewall -- else some rules/chains might be list!
+  - [systemctl, restart, docker.service]
+  - [systemctl, enable, --now, vector.service]
+  - [systemctl, enable, --now, actions.runner.service]
+  -
+    - bash
+    - -c
+    - |
+      echo "Pre-loading commonly used docker images from S3"
+      set -eux -o pipefail
+      aws s3 cp s3://airflow-ci-assets/pre-baked-images.tar.gz - | docker load
+
+write_files:
+  - path: /etc/systemd/system/actions.runner.service
+    content: |
+      [Unit]
+      Description=GitHub Actions Runner
+      After=network.target actions.runner-supervisor.service
+      Requires=actions.runner-supervisor.service
+      BindsTo=actions.runner-supervisor.service
+
+      [Service]
+      ExecStartPre=!/usr/local/sbin/runner-cleanup-workdir.sh
+      ExecStart=/home/runner/actions-runner/run.sh --once --startuptype service
+      ExecStop=/usr/local/bin/stop-runner-if-no-job.sh $MAINPID
+      EnvironmentFile=/etc/environment
+      Environment=GITHUB_ACTIONS_RUNNER_CHANNEL_TIMEOUT=300
+      User=runner
+      WorkingDirectory=/home/runner/actions-runner
+      KillMode=mixed
+      KillSignal=SIGTERM
+      TimeoutStopSec=5min
+      Restart=on-success
+
+      [Install]
+      WantedBy=multi-user.target
+
+  # Don't put this in ~runner, as these get written before the user is added, and this messes up creating the home dir
+  - path: /usr/local/sbin/runner-cleanup-workdir.sh
+    content: |
+      #!/bin/bash
+
+      if [[ -d ~runner/actions-runner/_work/airflow/airflow ]]; then
+        cd ~runner/actions-runner/_work/airflow/airflow
+
+        chown --changes -R runner: .
+        if [[ -e .git ]]; then
+          sudo -u runner bash -c "
+            git reset --hard && \
+            git submodule deinit --all -f && \
+            git submodule foreach git clean -fxd && \
+            git clean -fxd \
+          "
+        fi
+        docker ps -qa | xargs --no-run-if-empty docker rm -fv
+      fi
+    owner: root:root
+    permissions: '0775'
+  - path: /usr/local/bin/stop-runner-if-no-job.sh
+    content: |
+      #!/bin/bash
+      set -u
+
+      MAINPID="${MAINPID:-${1:-}}"
+
+      if [[ -z "$MAINPID" ]]; then
+         echo "No MAINPID, assuming it already crashed!"
+         exit 0
+      fi
+
+      if pgrep --ns $MAINPID -a Runner.Worker > /dev/null; then
+        echo "Waiting for current job to finish"
+        while pgrep --ns $MAINPID -a Runner.Worker; do
+          # Job running -- just wait for it to exit
+          sleep 10
+        done
+      fi
+
+      # Request shutdown if it's still alive -- because we are in "stop" state it should not restart
+      if pkill --ns $MAINPID Runner.Listener; then
+        # Wait for it to shut down
+        echo "Waiting for main Runner.Listener process to stop"
+        while pgrep --ns $MAINPID -a Runner.Listener; do
+          sleep 5
+        done
+      fi
+    owner: root:root
+    permissions: '0775'
+  - path: /etc/sudoers.d/runner
+    owner: root:root
+    permissions: '0440'
+    content: |
+      runner ALL=(ALL) NOPASSWD:/usr/sbin/swapoff -a, /usr/bin/rm -f /swapfile, /usr/bin/apt clean
+  - path: /etc/iptables/rules.v4
+    content: |
+      # Generated by iptables-save v1.8.4 on Thu Jan 14 13:59:27 2021
+      *filter
+      :INPUT ACCEPT [833:75929]
+      :FORWARD DROP [0:0]
+      :OUTPUT ACCEPT [794:143141]
+      :DOCKER-USER - [0:0]
+      -A FORWARD -j DOCKER-USER
+      # Dis-allow any docker container to access the metadata service
+      -A DOCKER-USER -d 169.254.169.254/32 -j REJECT --reject-with icmp-port-unreachable
+      -A DOCKER-USER -j RETURN
+      COMMIT
+
+  - path: /usr/local/sbin/actions-runner-ec2-reporting
+    permissions: '0775'
+    content: |
+      #!/bin/bash
+
+      if pgrep -c Runner.Worker >/dev/null; then
+          # Only report metric when we're doing something -- no point paying to submit zeros
+          aws cloudwatch put-metric-data --metric-name jobs-running --value "$(pgrep -c Runner.Worker)" --namespace github.actions
+      fi
+  - path: /etc/cron.d/cloudwatch-metrics-github-runners
+    content: |
+      */1 * * * * nobody /usr/local/sbin/actions-runner-ec2-reporting
+
+  - path: /etc/systemd/system/actions.runner-supervisor.service
+    content: |
+      [Unit]
+      Description=Fetch credentials and supervise GitHub Actions Runner
+      After=network.target
+      Before=actions.runner.service
+
+      [Service]
+      Type=notify
+      ExecStart=/opt/runner-supervisor/bin/python /opt/runner-supervisor/bin/runner-supervisor
+      # We need to run as root to have the ability to open the netlink connector socket
+      User=root
+      WorkingDirectory=/home/runner/actions-runner
+      Restart=always
+      EnvironmentFile=/etc/environment
+  - path: /etc/vector/vector.toml
+    content: |
+      data_dir = "/var/lib/vector"
+
+      [api]
+        enabled = true
+
+      # Input data. Change me to a valid input source.
+      [sources.logs]
+        type = "journald"
+        include_units = ["actions.runner.service", "actions.runner-supervisor.service"]
+
+      [sources.runner-logs]
+        type = "file"
+        include = ["/home/runner/actions-runner/_diag/*.log"]
+
+          [sources.runner-logs.multiline]
+            start_pattern = '^\[[0-9]{4}-[0-9]{2}-[0-9]{2}'
+            mode = "halt_before"
+            condition_pattern = '^\[[0-9]{4}-[0-9]{2}-[0-9]{2}'
+            timeout_ms = 250
+
+      [transforms.grok-runner-logs]
+        type = "grok_parser"
+        inputs=["runner-logs"]
+        pattern = "(?m)\\[%{TIMESTAMP_ISO8601:timestamp} %{LOGLEVEL:level} %{NOTSPACE:logger}\\] %{GREEDYDATA:message}"
+        types.timestamp = "timestamp|%F %TZ"
+
+      [transforms.without_systemd_fields]
+        type = "remove_fields"
+        inputs = ["logs"]
+        fields = ["_CAP_EFFECTIVE", "_SYSTEMD_SLICE", "_SYSTEMD_CGROUP",
+          "_SYSTEMD_INVOCATION_ID", "_SELINUX_CONTEXT", "_COMM", "_BOOT_ID",
+          "_MACHINE_ID", "_STREAM_ID", "_PID", "_GID", "_UID","_TRANSPORT",
+          "__MONOTONIC_TIMESTAMP", "SYSLOG_IDENTIFIER", "PRIORITY",
+          "source_type"]
+
+      # Output data
+      [sinks.cloudwatch]
+      inputs   = ["without_systemd_fields", "grok-runner-logs"]
+      type     = "aws_cloudwatch_logs"
+      encoding = "json"
+      create_missing_group = false
+      create_missing_stream = true
+      group_name = "GitHubRunners"
+      stream_name = "{{ host }}"
+      region = "eu-central-1"
+apt:
+  sources:
+    yarn:
+      source: "deb https://dl.yarnpkg.com/debian/ stable main"
+      keyid: "1646B01B86E50310"
+    timber:
+      source: "deb https://repositories.timber.io/public/vector/deb/ubuntu focal main"
+      key: |
+        -----BEGIN PGP PUBLIC KEY BLOCK-----
+        Version: GnuPG v2
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