Update test matrix strategy (#10)

.github/test-matrix.json

@@ -1,20 +1,35 @@
 {
-  "otp_version": ["24.0.4", "23.3.4.2", "22.3.4.20"],
-  "elixir_version": ["1.12.2", "1.11.4", "1.10.4"],
+  "otp_version": [
+    "24.0.6",
+    "23.3.4.7",
+    "22.3.4.21"
+  ],
+  "elixir_version": [
+    "1.12.3",
+    "1.11.4"
+  ],
+  "rebar3_version": [
+    "3.16.1"
+  ],
+  "os": [
+    "ubuntu-18.04"
+  ],
   "include": [
     {
       "otp_version": "21.3.8.24",
       "elixir_version": "1.10.4",
       "rebar3_version": "3.15.2"
+    },
+    {
+      "otp_version": "21.3.8.24",
+      "elixir_version": "1.11.4",
+      "rebar3_version": "3.15.2"
     }
   ],
   "exclude": [
     {
       "otp_version": "21.3.8.24",
-      "elixir_version": "1.12.2"
+      "elixir_version": "1.12.3"
     }
-  ],
-  "apps": [
-    "opentelemetry_phoenix"
   ]
 }

.github/workflows/elixir.yml

@@ -10,19 +10,22 @@ on:
       - 'main'
 
 jobs:
-  # test-matrix:
-  #   runs-on: ubuntu-latest
-  #   outputs:
-  #     matrix: ${{ steps.set-matrix.outputs.matrix }}
-  #   steps:
-  #     - uses: actions/checkout@v2
-  #     - name: Read file
-  #       id: set-matrix
-  #       run: |
-  #         echo "::set-output name=matrix::$(cat ./.github/test-matrix.json | jq -r -s '.|tojson')"
+  test-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Read file
+        id: set-matrix
+        run: |
+          matrixStringifiedObject="{\"otp_version\":[\"24.0.6\",\"23.3.4.7\",\"22.3.4.21\"],\"elixir_version\":[\"1.12.3\",\"1.11.4\"],\"rebar3_version\":[\"3.16.1\"],\"os\":[\"ubuntu-18.04\"],\"include\":[{\"otp_version\":\"21.3.8.24\",\"elixir_version\":\"1.10.4\",\"rebar3_version\":\"3.15.2\"},{\"otp_version\":\"21.3.8.24\",\"elixir_version\":\"1.11.4\",\"rebar3_version\":\"3.15.2\"}],\"exclude\":[{\"otp_version\":\"21.3.8.24\",\"elixir_version\":\"1.12.3\"}]}"
+          echo "::set-output name=matrix::$matrixStringifiedObject"
   opentelemetry-phoenix:
-    # needs: [test-matrix]
-    if: (contains(github.event.pull_request.labels.*.name, 'elixir') && contains(github.event.pull_request.labels.*.name, 'opentelemetry_phoenix'))
+    needs: [test-matrix]
+    if: (contains(github.event.pull_request.labels.*.name, 'elixir') && contains(github.event.pull_request.labels.*.name, 'opentelemetry_phoenix') && contains(github.event.pull_request.labels.*.name, 'scope-ci'))
+    env:
+      app: 'opentelemetry_phoenix'
     defaults:
       run:
         working-directory: instrumentation/${{ env.app }}
@@ -30,21 +33,7 @@ jobs:
     name: Opentelemetry Phoenix test on Elixir ${{ matrix.elixir_version }} (OTP ${{ matrix.otp_version }})
     strategy:
       fail-fast: false
-      matrix:
-        os: [ubuntu-18.04]
-        otp_version: ["24.0.4", "23.3.4.2", "22.3.4.20"]
-        elixir_version: ["1.12.2", "1.11.4"]
-        rebar3_version: ["3.16.1"]
-        include:
-          - otp_version: '21.3.8.24'
-            elixir_version: '1.11.4'
-            rebar3_version: '3.15.2'
-            os: ubuntu-18.04
-        exclude:
-          - otp_version: '21.3.8.24'
-            elixir_version: '1.12.1'
-    env:
-      app: 'opentelemetry_phoenix'
+      matrix: ${{ fromJson(needs.test-matrix.outputs.matrix) }}
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1

CONTRIBUTING.md

@@ -0,0 +1,18 @@
+## Contributing
+
+
+### CI
+
+Given the number of projects in this repo and the wide matrix of OTP/Elixir versions we must
+test against, it is important to scope test jobs to the smallest subset of test possible. Project test jobs should utilize the test matrix strategy outputted by the `test-matrix` job.
+
+### Test Matrix Updates
+
+As new OTP and Elixir versions are released, the test matrix must be updated. A beautified version of the [test matrix](https://github.com/open-telemetry/opentelemetry-erlang-contrib/blob/main/.github/test-matrix.json) is kept for easy editing.
+
+Updating the file:
+
+1. Update the beautified json file (this is the form you'll commit)
+2. Uglify and escape the json object
+3. Copy this final value to the `test-matrix` job output
+