Added instructions for releasing to the test environment

architecture/smg/04-smg-creating-a-release.md

@@ -21,3 +21,33 @@ Versioning is done via a combination of tags on the repository and [git describe
 Tagging triggers a rebuild of all artifacts. Git tags must be [annotated](https://git-scm.com/book/en/v2/Git-Basics-Tagging)
 with the same version before pushing to GitHub otherwise the version is not correctly
 picked up.
+
+## Releasing to the test environment
+
+Below are some instructions for releasing a build to the test environment.
+Using an ssh tunnel is recommended to make this easier, which is outlined in
+the [design section](./02-smg-design.md) of the SMG.
+
+There is some further information in the
+[datalab-k8s-manifests](https://github.com/NERC-CEH/datalab-k8s-manifests)
+repo, as that repo is used as part of this process.
+
+1. Write code; Create pull request; Merge into master.
+1. After merging, a new release of the Docker image should be created and can be found on
+   [Docker Hub](https://hub.docker.com/r/nerc/datalab-app/tags?page=1&ordering=last_updated).
+    * Get the Docker image tag of the correct build - to do this,
+      compare the tag to the desired git commit, looking after the `g` in the tag.
+    * For example, if your git commit hash starts with `abcd1234`,
+      then the Docker tag might look something like `0.12.34-gabcd1234`.
+1. Open the `datalab-k8s-manifests` repo and go to the `helm/datalab/Chart.yaml` file.
+    Update the `appVersion` and increment the `version`.
+1. Switch to the `datalabs` context in `kubectl`, i.e. `kubectx datalabs`.
+1. Switch to the `test` namespace in `kubectl`, i.e. `kubens test`.
+1. Run Helm to perform the release:
+    * `helm dependency build ./helm/datalab/`
+    * `helm upgrade datalab ./helm/datalab`
+1. Check that the release is successful:
+    * Inspect the pods with `kubectl get pods`.
+    * Go to the test environment website to view the changes.
+1. When happy with the changes, make a pull request in the `datalab-k8s-manifests`
+    repo for the helm chart change.