fix(docker_refresh): Skip recreation for unchanged images

docker_refresh.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
 # /// script
 # dependencies = []
 # ///
@@ -22,6 +22,7 @@ class Project:
     files: tuple[Path, ...]
     environment_files: tuple[Path, ...]
     services: set[str] = field(default_factory=set)
+    running_images: dict[str, set[str]] = field(default_factory=dict)
 
     def command(self) -> list[str]:
         command = [
@@ -116,6 +117,7 @@ def discover_projects(containers: list[dict[str, Any]], selected_projects: set[s
         if (existing.directory, existing.files, existing.environment_files) != (project.directory, project.files, project.environment_files):
             raise ValueError(f"Project {name}: containers have inconsistent Compose file labels")
         existing.services.add(service)
+        existing.running_images.setdefault(service, set()).add(container.get("Image") or "")
     return sorted(projects.values(), key=lambda project: project.name)
 
 
@@ -148,13 +150,30 @@ def refresh_project(project: Project, dry_run: bool) -> None:
             services.append(name)
     if not services:
         return
-    for arguments in (
+    pull_command = [*command, "pull", "--policy", "always", *services]
-        ["pull", "--policy", "always", *services],
+    logging.info("%s", shlex.join(pull_command))
-        ["up", "--detach", "--no-deps", "--no-build", "--pull", "never", *services],
-    ):
-        logging.info("%s", shlex.join([*command, *arguments]))
     if not dry_run:
-            subprocess.run(args=[*command, *arguments], cwd=project.directory, check=True)
+        subprocess.run(args=pull_command, cwd=project.directory, check=True)
+        changed_services = []
+        for name in services:
+            result = subprocess.run(
+                args=["docker", "image", "inspect", "--format", "{{.Id}}", configured_services[name]["image"]],
+                check=True, capture_output=True, text=True, timeout=60,
+            )
+            image_id = result.stdout.strip()
+            if not image_id:
+                raise ValueError(f"Project {project.name}: image ID is missing for service {name}")
+            if project.running_images.get(name) == {image_id}:
+                logging.info("Skipping %s/%s: running image is up to date", project.name, name)
+            else:
+                changed_services.append(name)
+        services = changed_services
+    if not services:
+        return
+    up_command = [*command, "up", "--detach", "--no-deps", "--no-build", "--pull", "never", *services]
+    logging.info("%s", shlex.join(up_command))
+    if not dry_run:
+        subprocess.run(args=up_command, cwd=project.directory, check=True)
 
 
 def main() -> int:

docker_refresh_test.py

@@ -46,6 +46,7 @@ def test_discovery_filters_and_groups_replicas(selected: set[str], expected: lis
         ("app:latest", True, "False", "other"),
     ]:
         containers.append({
+            "Image": "sha256:running",
             "State": {"Running": running},
             "Config": {"Image": image, "Labels": {
                 "com.docker.compose.project": project,
@@ -60,6 +61,7 @@ def test_discovery_filters_and_groups_replicas(selected: set[str], expected: lis
     assert [project.name for project in projects] == expected
     for project in projects:
         assert project.services == {"app"}
+        assert project.running_images == {"app": {"sha256:running"}}
         assert project.files == (Path("/srv/web/compose.yml"), Path("/srv/web/override.yml"))
         assert "--env-file" in project.command()
 
@@ -104,12 +106,45 @@ def test_refresh_commands_and_current_config_filtering(tmp_path: Path, dry_run:
             "db": {"image": "db:16"},
         },
     }))
-    with patch.object(script.subprocess, "run", return_value=response) as run:
+    image_response = subprocess.CompletedProcess(args=[], returncode=0, stdout="sha256:new\n")
+    with patch.object(script.subprocess, "run", side_effect=[response, response, image_response, response]) as run:
         script.refresh_project(project=project, dry_run=dry_run)
-    assert run.call_count == (1 if dry_run else 3)
+    assert run.call_count == (1 if dry_run else 4)
     if not dry_run:
         assert run.call_args_list[1].kwargs["args"] == [*project.command(), "pull", "--policy", "always", "app"]
-        assert run.call_args_list[2].kwargs["args"] == [*project.command(), "up", "--detach", "--no-deps", "--no-build", "--pull", "never", "app"]
+        assert run.call_args_list[2].kwargs["args"] == ["docker", "image", "inspect", "--format", "{{.Id}}", "app:latest"]
+        assert run.call_args_list[3].kwargs["args"] == [*project.command(), "up", "--detach", "--no-deps", "--no-build", "--pull", "never", "app"]
+
+
+@pytest.mark.parametrize("running_images, expected_services", [
+    ({"app": {"sha256:current"}, "worker": {"sha256:current"}}, []),
+    ({"app": {"sha256:old"}, "worker": {"sha256:current"}}, ["app"]),
+    ({"app": {"sha256:current", "sha256:old"}, "worker": {"sha256:current"}}, ["app"]),
+    ({"app": {"sha256:old"}, "worker": {"sha256:old"}}, ["app", "worker"]),
+])
+def test_only_changed_services_are_redeployed(
+    tmp_path: Path, running_images: dict[str, set[str]], expected_services: list[str],
+) -> None:
+    compose = tmp_path / "compose.yml"
+    compose.touch()
+    project = script.Project(
+        name="web", directory=tmp_path, files=(compose,), environment_files=(),
+        services={"app", "worker"}, running_images=running_images,
+    )
+    configuration = subprocess.CompletedProcess(args=[], returncode=0, stdout=json.dumps({
+        "services": {"app": {"image": "app:latest"}, "worker": {"image": "worker:latest"}},
+    }))
+    image_response = subprocess.CompletedProcess(args=[], returncode=0, stdout="sha256:current\n")
+    with patch.object(script.subprocess, "run", side_effect=[
+        configuration, configuration, image_response, image_response, configuration,
+    ]) as run:
+        script.refresh_project(project=project, dry_run=False)
+    assert run.call_args_list[1].kwargs["args"] == [*project.command(), "pull", "--policy", "always", "app", "worker"]
+    assert run.call_count == (5 if expected_services else 4)
+    if expected_services:
+        assert run.call_args.kwargs["args"] == [
+            *project.command(), "up", "--detach", "--no-deps", "--no-build", "--pull", "never", *expected_services,
+        ]
 
 
 @pytest.mark.parametrize("build", [".", {"context": "."}])