fix: release only when image contents change (#25)

.github/scripts/compute_image_fingerprint.py

@@ -0,0 +1,133 @@
+#!/usr/bin/env python3
+"""Compute a stable fingerprint for the runtime contents of a local Docker image."""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import subprocess
+import sys
+import tarfile
+import tempfile
+from pathlib import Path
+
+
+def run(*args: str) -> str:
+    completed = subprocess.run(
+        list(args),
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+    return completed.stdout
+
+
+def hash_stream(fileobj) -> str:
+    digest = hashlib.sha256()
+    while True:
+        chunk = fileobj.read(1024 * 1024)
+        if not chunk:
+            break
+        digest.update(chunk)
+    return digest.hexdigest()
+
+
+def normalized_config(image_ref: str) -> bytes:
+    inspect_payload = json.loads(run("docker", "image", "inspect", image_ref))[0]
+    config_payload = {
+        "architecture": inspect_payload.get("Architecture"),
+        "os": inspect_payload.get("Os"),
+        "variant": inspect_payload.get("Variant"),
+        "config": inspect_payload.get("Config", {}),
+    }
+    return json.dumps(
+        config_payload,
+        sort_keys=True,
+        separators=(",", ":"),
+    ).encode("utf-8")
+
+
+def normalized_tar_entries(tar_path: Path) -> list[str]:
+    records: list[str] = []
+    with tarfile.open(tar_path, mode="r") as archive:
+        for member in archive.getmembers():
+            path = member.name.rstrip("/") or "."
+            record: dict[str, object] = {
+                "path": path,
+                "mode": member.mode,
+            }
+
+            if member.isdir():
+                record["type"] = "dir"
+            elif member.isfile():
+                extracted = archive.extractfile(member)
+                if extracted is None:
+                    raise RuntimeError(f"Unable to read file contents for {path}")
+                with extracted:
+                    record["type"] = "file"
+                    record["sha256"] = hash_stream(extracted)
+            elif member.issym():
+                record["type"] = "symlink"
+                record["target"] = member.linkname
+            elif member.islnk():
+                record["type"] = "hardlink"
+                record["target"] = member.linkname
+            elif member.ischr():
+                record["type"] = "char"
+                record["device"] = [member.devmajor, member.devminor]
+            elif member.isblk():
+                record["type"] = "block"
+                record["device"] = [member.devmajor, member.devminor]
+            elif member.isfifo():
+                record["type"] = "fifo"
+            else:
+                record["type"] = f"other:{member.type!r}"
+                if member.linkname:
+                    record["target"] = member.linkname
+
+            records.append(
+                json.dumps(record, sort_keys=True, separators=(",", ":"))
+            )
+
+    records.sort()
+    return records
+
+
+def main() -> int:
+    if len(sys.argv) != 2:
+        print("usage: compute_image_fingerprint.py <local-image-ref>", file=sys.stderr)
+        return 2
+
+    image_ref = sys.argv[1]
+    container_id = run("docker", "create", image_ref).strip()
+
+    try:
+        with tempfile.TemporaryDirectory(prefix="clawmanager-image-export-") as temp_dir:
+            tar_path = Path(temp_dir) / "filesystem.tar"
+            subprocess.run(
+                ["docker", "export", "-o", str(tar_path), container_id],
+                check=True,
+            )
+
+            digest = hashlib.sha256()
+            digest.update(normalized_config(image_ref))
+            digest.update(b"\n")
+
+            for record in normalized_tar_entries(tar_path):
+                digest.update(record.encode("utf-8"))
+                digest.update(b"\n")
+
+            print(digest.hexdigest())
+    finally:
+        subprocess.run(
+            ["docker", "rm", "-f", container_id],
+            check=False,
+            stdout=subprocess.DEVNULL,
+            stderr=subprocess.DEVNULL,
+        )
+
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

.github/workflows/release.yml

@@ -33,30 +33,16 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: Build candidate image
+        shell: bash
+        run: |
+          docker build --pull -t clawmanager:release-candidate .
+
       - name: Compute release fingerprint
         shell: bash
         run: |
-          set -euo pipefail
-
-          mapfile -t release_files < <(git ls-files -- \
-            Dockerfile \
-            .dockerignore \
-            frontend \
-            backend \
-            deployments/container/start.sh \
-            deployments/nginx/nginx.conf)
-
-          mapfile -t base_images < <(awk 'toupper($1)=="FROM" { print $2 }' Dockerfile)
-
-          {
-            for image in "${base_images[@]}"; do
-              printf 'base-image %s\n' "$image"
-            done
-
-            for file in "${release_files[@]}"; do
-              sha256sum "$file"
-            done
-          } | sha256sum | awk '{print "IMAGE_FINGERPRINT="$1}' >> "$GITHUB_ENV"
+          IMAGE_FINGERPRINT="$(python3 .github/scripts/compute_image_fingerprint.py clawmanager:release-candidate)"
+          echo "IMAGE_FINGERPRINT=${IMAGE_FINGERPRINT}" >> "$GITHUB_ENV"
 
       - name: Read latest release fingerprint
         id: latest-release
@@ -94,6 +80,12 @@ jobs:
           LAST_FINGERPRINT="${LAST_FINGERPRINT//\`/}"
           CURRENT_FINGERPRINT="${CURRENT_FINGERPRINT//\`/}"
 
+          if git rev-parse "$TAG_NAME" >/dev/null 2>&1; then
+            echo "should_release=false" >> "$GITHUB_OUTPUT"
+            echo "tag_name=" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
           if [ "$FORCE_RELEASE" = "true" ]; then
             echo "should_release=true" >> "$GITHUB_OUTPUT"
             echo "tag_name=$TAG_NAME" >> "$GITHUB_OUTPUT"
@@ -106,12 +98,6 @@ jobs:
             exit 0
           fi
 
-          if git rev-parse "$TAG_NAME" >/dev/null 2>&1; then
-            echo "should_release=false" >> "$GITHUB_OUTPUT"
-            echo "tag_name=" >> "$GITHUB_OUTPUT"
-            exit 0
-          fi
-
           echo "should_release=true" >> "$GITHUB_OUTPUT"
           echo "tag_name=$TAG_NAME" >> "$GITHUB_OUTPUT"
 
@@ -152,35 +138,27 @@ jobs:
           fi
           echo "IMAGE_URI=ghcr.io/${REPOSITORY_OWNER_LOWER}/clawmanager" >> "$GITHUB_ENV"
 
-      - name: Compute release fingerprint
-        shell: bash
-        run: |
-          set -euo pipefail
-
-          mapfile -t release_files < <(git ls-files -- \
-            Dockerfile \
-            .dockerignore \
-            frontend \
-            backend \
-            deployments/container/start.sh \
-            deployments/nginx/nginx.conf)
-
-          mapfile -t base_images < <(awk 'toupper($1)=="FROM" { print $2 }' Dockerfile)
-
-          {
-            for image in "${base_images[@]}"; do
-              printf 'base-image %s\n' "$image"
-            done
-
-            for file in "${release_files[@]}"; do
-              sha256sum "$file"
-            done
-          } | sha256sum | awk '{print "IMAGE_FINGERPRINT="$1}' >> "$GITHUB_ENV"
-
       - name: Checkout release tag
         if: github.event_name != 'push'
         run: git checkout "${TAG_NAME}"
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build release image
+        shell: bash
+        run: |
+          docker build --pull \
+            -t "${IMAGE_URI}:${TAG_NAME}" \
+            -t "${IMAGE_URI}:latest" \
+            .
+
+      - name: Compute release fingerprint
+        shell: bash
+        run: |
+          IMAGE_FINGERPRINT="$(python3 .github/scripts/compute_image_fingerprint.py "${IMAGE_URI}:${TAG_NAME}")"
+          echo "IMAGE_FINGERPRINT=${IMAGE_FINGERPRINT}" >> "$GITHUB_ENV"
+
       - name: Log in to GHCR
         uses: docker/login-action@v3
         with:
@@ -188,21 +166,23 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+      - name: Push release image
+        shell: bash
+        run: |
+          docker push "${IMAGE_URI}:${TAG_NAME}"
+          docker push "${IMAGE_URI}:latest"
 
-      - name: Build and push release image
-        id: docker-build
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: ./Dockerfile
-          push: true
-          tags: |
-            ${{ env.IMAGE_URI }}:${{ env.TAG_NAME }}
-            ${{ env.IMAGE_URI }}:latest
+      - name: Read pushed image digest
+        shell: bash
+        run: |
+          IMAGE_DIGEST="$(docker buildx imagetools inspect "${IMAGE_URI}:${TAG_NAME}" | sed -n 's/^Digest:[[:space:]]*//p' | head -n1)"
+          if [ -z "${IMAGE_DIGEST}" ]; then
+            echo "Failed to resolve image digest for ${IMAGE_URI}:${TAG_NAME}" >&2
+            exit 1
+          fi
+          echo "IMAGE_DIGEST=${IMAGE_DIGEST}" >> "$GITHUB_ENV"
 
-      - name: Build release highlights
+      - name: Build release notes
         shell: bash
         run: |
           cat <<EOF > /tmp/release-highlights.md
@@ -217,7 +197,7 @@ jobs:
 
           Image: \`${IMAGE_URI}:${TAG_NAME}\`
           Latest: \`${IMAGE_URI}:latest\`
-          Image-Digest: \`${{ steps.docker-build.outputs.digest }}\`
+          Image-Digest: \`${IMAGE_DIGEST}\`
           Build-Fingerprint: \`${IMAGE_FINGERPRINT}\`
           EOF
 

Dockerfile

@@ -18,7 +18,7 @@ COPY backend/go.mod backend/go.sum ./
 RUN go mod download
 
 COPY backend/ ./
-RUN CGO_ENABLED=0 GOOS=linux go build -o /out/clawreef-server ./cmd/server
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -buildvcs=false -ldflags="-s -w -buildid=" -o /out/clawreef-server ./cmd/server
 
 FROM nginx:1.27-alpine