Merge all parallel benchmarks after they complete

.github/workflows/test.yml

@@ -45,16 +45,37 @@ jobs:
           key: v4-build-tox-cache-${{ env.RUN_MATRIX_COMBINATION }}-${{ hashFiles('tox.ini', 'gen-requirements.txt', 'dev-requirements.txt') }}
       - name: run tox
         run: tox -f ${{ matrix.python-version }}-${{ matrix.package }} -- --benchmark-json=${{ env.RUN_MATRIX_COMBINATION }}-benchmark.json
-      - name: Find and merge benchmarks
+      - name: Find and merge ${{ matrix.package }} benchmarks
         # TODO: Add at least one benchmark to every package type to remove this (#249)
         if: matrix.package == 'sdkextension' || matrix.package == 'propagator'
         run: >-
+          mkdir -p benchmarks;
           jq -s '.[0].benchmarks = ([.[].benchmarks] | add)
           | if .[0].benchmarks == null then null else .[0] end'
-          **/**/tests/*${{ matrix.package }}*-benchmark.json > output.json
+          **/**/tests/*${{ matrix.package }}*-benchmark.json > benchmarks/output_${{ matrix.package }}.json
+      - name: upload layer arn artifact
+        if: ${{ success() }}
+        uses: actions/upload-artifact@v2
+        with:
+          name: benchmarks
+          path: benchmarks/output_${{ matrix.package }}.json
+  combine-benchmarks:
+    runs-on: ubuntu-latest
+    needs: build
+    if: ${{ always() }}
+    name: Combine benchmarks from previous build job
+    steps:
+      - name: download layerARNs
+        uses: actions/download-artifact@v2
+        with:
+          name: benchmarks
+          path: benchmarks
+      - name: Find and merge all benchmarks
+        run: >-
+          jq -s '.[0].benchmarks = ([.[].benchmarks] | add)
+          | if .[0].benchmarks == null then null else .[0] end'
+          benchmarks/output_*.json > output.json;
       - name: Report on benchmark results
-        # TODO: Add at least one benchmark to every package type to remove this (#249)
-        if: matrix.package == 'sdkextension' || matrix.package == 'propagator'
         uses: benchmark-action/github-action-benchmark@v1
         with:
           name: OpenTelemetry Python Benchmarks - Python ${{ env[matrix.python-version ]}} - ${{ matrix.package }}