FEATURE: print out compressed image sizes for amd64 (#887)

print out compressed image sizes for amd64 in a build step for PRs. Allows for PRs to be automatically reviewed for space efficiency

.github/workflows/build.yml

@@ -45,6 +45,11 @@ jobs:
     needs: timestamp
     env:
       TIMESTAMP: ${{ needs.timestamp.outputs.timestamp }}
+    services:
+      registry:
+        image: registry:2
+        ports:
+          - 5000:5000
     steps:
       - uses: actions/checkout@v3
         with:
@@ -103,6 +108,21 @@ jobs:
         run: |
           docker images discourse/base
 
+      - name: Print compressed summary
+        if: github.event_name == 'pull_request' && matrix.arch == 'amd64'
+        run: |
+          # Push to local repo to compare sizes
+          docker tag discourse/base:2.0.${{ env.TIMESTAMP }}-slim-${{ matrix.arch }} localhost:5000/base:2.0.${{ env.TIMESTAMP }}-slim-${{ matrix.arch }}
+          docker tag discourse/base:2.0.${{ env.TIMESTAMP }}-main-${{ matrix.arch }} localhost:5000/base:2.0.${{ env.TIMESTAMP }}-main-${{ matrix.arch }}
+          docker push --quiet localhost:5000/base:2.0.${{ env.TIMESTAMP }}-slim-${{ matrix.arch }}
+          docker push --quiet localhost:5000/base:2.0.${{ env.TIMESTAMP }}-main-${{ matrix.arch }}
+          # multiarch manifest is an array of schemas - [0] is amd64, [1] is arch64: Compare amd64.
+          CURRENT_SLIM=$(docker manifest inspect -v discourse/base:slim | jq -r '.[0].SchemaV2Manifest.layers[] | .size / 1024 / 1024 | .*100 | round/100' | awk '{print $0; sum+= $0}; END {print sum}' | tail -n 1)
+          CURRENT_RELEASE=$(docker manifest inspect -v discourse/base:release | jq -r '.[0].SchemaV2Manifest.layers[] | .size / 1024 / 1024 | .*100 | round/100' | awk '{print $0; sum+= $0}; END {print sum}' | tail -n 1)
+          NEW_SLIM=$(docker manifest inspect -v --insecure localhost:5000/base:2.0.${{ env.TIMESTAMP }}-slim-${{ matrix.arch }} |  jq -r '.SchemaV2Manifest.layers[] | .size / 1024 / 1024 | .*100 | round/100' | awk '{print $0; sum+= $0}; END {print sum}' | tail -n 1)
+          NEW_RELEASE=$(docker manifest inspect -v --insecure localhost:5000/base:2.0.${{ env.TIMESTAMP }}-main-${{ matrix.arch }} | jq -r '.SchemaV2Manifest.layers[] | .size / 1024 / 1024 | .*100 | round/100' | awk '{print $0; sum+= $0}; END {print sum}' | tail -n 1)
+          echo "current slim: ${CURRENT_SLIM}MB release: ${CURRENT_RELEASE}MB. new slim: ${NEW_SLIM}MB release: ${NEW_RELEASE}MB"
+
       - name: push to dockerhub
         if: github.ref == 'refs/heads/main'
         env: