Add snap release workflow (#53)

* Add snap release workflow

* Remove arm arch to avoid confusion and change input to match bootstack-action repo

---------

Co-authored-by: Andrea Ieri <[email protected]>

.github/workflows/release.yaml

@@ -0,0 +1,25 @@
+name: Publish snap
+
+on:
+  push:
+    branches:
+      - '[0-9].[0-9]+'
+      - main
+      - master
+  workflow_dispatch:
+
+jobs:
+  publish:
+    uses: canonical/bootstack-actions/.github/workflows/snap-release.yaml@main
+    secrets: inherit
+    with:
+      python-version-unit: "['3.8', '3.10']"
+      python-version-func: "3.10"
+      tox-version: "<4"
+      snapcraft: true
+      commands: "['make functional']"
+      # "channel" should be one or a (comma-separated) list of <track>/<risk-level>
+      # Check if the current branch is the default ("main" or "master"). If true, track is set to "latest";
+      # otherwise, use the versioned branch name as the track name
+      # The risk level we want to release the snap to is "edge"
+      channel: ${{ contains(fromJSON('["main", "master"]'), github.ref_name) && 'latest' || github.ref_name }}/edge

README.md

@@ -7,6 +7,13 @@ To get the latest stable version of the snap from Snapstore, run:
 ```bash
 sudo snap install prometheus-juju-exporter
 ```
+
+To install snap from a specific channel, e.g. `2.9/stable`, use `--channel` flag:
+```bash
+sudo snap install prometheus-juju-exporter --channel 2.9/stable
+```
+**Note**: please refer to [Juju Version Compatibility](#juju-version-compatibility) to select the proper snap channel depending on the version of the juju controller that the snap will communicate with.
+
 To get the latest development version of the snap, build from the source code and install with `--dangerous` flag:
 ```bash
 make build
@@ -19,3 +26,12 @@ By default, prometheus-juju-exporter uses the configuration specified in [config
 The snap requires juju user's credentials to connect to a controller and all of its models. The credentials are set as `juju.username` and `juju.password` config values. Normally, **`superuser`** privilege is expected for such a user for full access to the controller. However, in case it is not possible, the minimum privilege requirements are:
 1. `login` access to the controller instance and `admin` access to the model hosting the controller
 2. `admin` access to any model that's expected to be monitored by this exporter
+
+
+## Juju Version Compatibility
+Due to the limitations of libjuju's cross-version support, channels and versions are used in the snap to accommodate different juju controller versions. The following table demonstrates the compatibility matrix between juju controller version, snap channel, snap version, and branch in the repository. The operator should select the proper snap channel at installation time accordingly.
+
+| Juju Controller Version | Snap Channel                              | Repo Branch | Snap Version |
+|-------------------------|-------------------------------------------|-------------|--------------|
+| 2.8 and older           | 2.8/stable<br/>2.8/candidate<br/>2.8/edge | 2.8         | 1.x          |
+| 2.9                     | 2.9/stable<br/>2.9/candidate<br/>2.9/edge | 2.9         | 2.x          |

snap/snapcraft.yaml

@@ -7,8 +7,7 @@ description: |
   Collects juju machine status metrics periodically.
   Provides a prometheus exporter interface exposing the collected metrics.
 architectures:
-  - amd64
-  - arm64
+  - build-on: amd64
 
 grade: stable
 confinement: strict