Experiment with PDF generation

Signed-off-by: David Young <davidy@funkypenguin.co.nz>

docs/recipes/gitlab-runner.md

@@ -0,0 +1,97 @@
+---
+title: How to run Gitlab Runner in Docker
+---
+
+# Gitlab Runner
+
+Some features of GitLab require a "[runner](https://docs.gitlab.com/runner/)" (_in the sense of a "gopher" or a "minion"_). A runner "registers" itself with a GitLab instance, and is given tasks to run. Tasks include running Continuous Integration (CI) builds, and building container images.
+
+While a runner isn't strictly required to use GitLab, if you want to do CI, you'll need at least one. There are many ways to deploy a runner - this recipe focuses on the docker container model.
+
+## Ingredients
+
+!!! summary "Ingredients"
+Existing:
+
+    1. [X] [Docker swarm cluster](/docker-swarm/design/) with [persistent shared storage](/docker-swarm/shared-storage-ceph/)
+    2. [X] [Traefik](/docker-swarm/traefik) configured per design
+    3. [X] DNS entry for the hostname you intend to use, pointed to your [keepalived](/docker-swarm/keepalived/) IP
+    4. [X] [GitLab](/recipes/gitlab) installation (see previous recipe)
+
+## Preparation
+
+### Setup data locations
+
+We'll need several directories to bind-mount into our runner containers, so create them in `/var/data/gitlab`:
+
+```bash
+mkdir -p /var/data/gitlab/runners/{1,2}
+```
+
+### Setup Docker Swarm
+
+Create a docker swarm config file in docker-compose syntax (v3), something like this:
+
+--8<-- "premix-cta.md"
+
+```yaml
+version: '3'
+
+services:
+  thing1:
+    image: gitlab/gitlab-runner
+    volumes:
+    - /var/data/gitlab/runners/1:/etc/gitlab-runner
+    networks:
+    - internal
+
+  thing2:
+    image: gitlab/gitlab-runner
+    volumes:
+    - /var/data/gitlab/runners/2:/etc/gitlab-runner
+    networks:
+    - internal
+
+networks:
+  internal:
+    driver: overlay
+    ipam:
+      config:
+        - subnet: 172.16.23.0/24
+```
+
+### Configure runners
+
+From your GitLab UI, you can retrieve a "token" necessary to register a new runner. To register the runner, you can either create config.toml in each runner's bind-mounted folder (example below), or just `docker exec` into each runner container and execute `gitlab-runner register` to interactively generate config.toml.
+
+Sample runner config.toml:
+
+```ini
+concurrent = 1
+check_interval = 0
+
+[[runners]]
+  name = "myrunner1"
+  url = "https://gitlab.example.com"
+  token = "<long string here>"
+  executor = "docker"
+  [runners.docker]
+    tls_verify = false
+    image = "ruby:2.1"
+    privileged = false
+    disable_cache = false
+    volumes = ["/cache"]
+    shm_size = 0
+  [runners.cache]
+```
+
+## Serving
+
+### Launch runners
+
+Launch the GitLab Runner stack by running `docker stack deploy gitlab-runner -c <path -to-docker-compose.yml>`
+
+[^1]: You'll note that I setup 2 runners. One is locked to a single project (_this cookbook build_), and the other is a shared runner. I wanted to ensure that one runner was always available to run CI for this project, even if I'd tied up another runner on something heavy-duty, like a container build. Customize this to your use case.
+[^2]: Originally I deployed runners in the same stack as GitLab, but I found that they would frequently fail to start properly when I launched the stack. I think that this was because the runners started so quickly (_and GitLab starts **sooo** slowly!_), that they always started up reporting that the GitLab instance was invalid or unavailable. I had issues with CI builds stuck permanently in a "pending" state, which were only resolved by restarting the runner. Having the runners deployed in a separate stack to GitLab avoids this problem.
+
+--8<-- "recipe-footer.md"