add drone ci

blogs/2022/10/17/drone-ci.md

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+# Drone CI
+
+When it comes to automation, [GitLab CI](https://gitlab.com) has been my go-to for running builds, tests and deployments of projects from static websites to 3D open-world games.
+This has generally been on a self-hosted installation, and often makes use of physical runners.
+However, I have some gripes: I mostly only use it for the CI, but it comes with an issue tracker and Git hosting solution too - great for some cases, but overkill in so many others.
+Because it's such a complete solution, GitLab is a bit of a resource hog, and can often run frustratingly slowly.
+
+Recently I've been playing with a friend's self-hosted instance of [Drone CI](https://drone.io/) as a lightweight alternative, and I much prefer it.
+I didn't set up the instance, so that part is out of scope for this post, but in case it's relevant, we're using a self-hosted [Gitea](gitea.io) instance to host the source.
+You can find out about configuring Drone with Gitea [here](https://docs.drone.io/server/provider/gitea/).
+
+
+## Yet Another Yaml Config
+
+Like GitLab, Drone is configured via a YAML file at the project root, called `.drone.yml`.
+Drone is configured by creating 'steps' to the pipeline, where GitLab uses 'jobs'.
+
+My first project's automation requirements were small - all I needed for a deployment was to copy all the files in a directory on every push to the `main` branch.
+This means I needed secure access to the host, and the ability to copy files to it.
+I didn't want to dedicate any permanent resources to such a small project, so opted for the `docker` pipeline option.
+
+My pipeline would contain a single `deploy` step which would configure SSH access to the host, and then use it to copy the relevant files from the checked out version of the project.
+I decided to use `ubuntu` as the Docker image for familiarity and accessibility - there are probably better options.
+Drone widely supports Docker image registries; I have not used Docker much, but would like to get more experience with it.
+
+```yml
+kind: pipeline
+type: docker
+name: deploy
+
+steps:
+- name: deploy
+  image: ubuntu
+  when:
+    branch:
+    - main
+
+  commands:
+    - echo hello world
+```
+
+## Secrets
+
+A hugely important aspect of automation is ensuring the security of one's pipelines.
+Automated access between pipelines is a big risk, and should be locked down as much as possible.
+For passing around secrets such as passwords and SSH keys, Drone has a concept of secrets.
+I created a private key on my local machine for the runner's access to the remote host, and added a [per-repository secret](https://docs.drone.io/secret/repository/) to contain the value.
+This is a named string value which can be accessed from within the context of a single pipeline step.
+
+I also created secrets to contain values for the remote host address and the user to login as.
+These are less of a security concern than the private SSH key, but we should obfuscate them anyway.
+It's also a useful step towards generalising the pipeline for other projects: I can use the same set of commands in multiple CI configurations, and just update the secrets from the project page.
+
+This block was placed in the same step definition as above, below the `image:` entry:
+
+```
+environment:
+  HOST:
+    from_secret: host
+  USER:
+    from_secret: user
+  SSH_KEY:
+    from_secret: ssh_key
+```
+
+## Connecting
+
+To use the SSH key, we need to spin up `ssh-agent` and load our key into it.
+Since it's passed into the job as an environment variable, this involves first writing it to a file.
+We also need to disable host key checking (the bit that asks if you're sure you want to connect to a new host) as we're making an automated SSH connection, and therefore won't be there to type 'yes'.
+
+```yml
+# configure ssh
+- eval $(ssh-agent -s)
+- mkdir -p ~/.ssh
+- echo "$SSH_KEY" > ~/.ssh/id_rsa
+- chmod 600 ~/.ssh/id_rsa
+- ssh-add
+- echo "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config
+```
+
+Finally, it's time to run some SSH commands.
+I had a bit of trouble getting the hang of variable templating here - it took some trial and error to figure out what variables would get expanded and when.
+Since my `HOST` and `USER` values are defined in secrets, I had to get them from my evironment variables and into a correctly formatted string for the SSH target.
+As I would be running multiple commands, I also wanted to store this in a variable to keep the SSH commands short in the Drone config.
+
+What ended up working for me was this:
+
+```yml
+# environment variables get expanded (twice?)
+- host="$${USER}@$${HOST}"
+# running 'hostname' on the deploy target
+- ssh $host "hostname"
+```
+
+## Images
+
+It's pretty cool to be able to pass a repository through several Docker images through the pipeline.
+I have my website's Makefile set up to build off my local machine, which is on Arch.
+It therefore depends on Arch-specific package names.
+I didn't want to have to hack around my existing build configuration just to build it automatically, but I also found that the deploy steps I'd already written worked best on Ubuntu.
+
+For Drone, this is no problem - I can simply specify `image: archlinux` in the build stage, and `image: ubuntu` for the deploy step.
+My Makefile and local workflow requires no changes at all, but I can still use the more robust deploy steps from Ubuntu.
+
+## Final thoughts
+
+I like Drone's minimalist approach to CI.
+There isn't much in terms of configuration, and the interface is much snappier than Gitlab's.
+It will take a bit more work to get a full workflow - Gitlab basically has one out the box - but working with more separate components should provide flexibility and resilience in the long run.
+
+I'd like to explore some more features, like [templates](https://docs.drone.io/template/yaml/) for steps shared between repositories, and spend more time tuning exactly when pipelines run.
+I also want to try building some more complex projects, such as those using game engines like Godot, and those targeting multiple target platforms.
+Those are adventures for another day, though.
+
+That's all for now, thanks for reading and see you next time!