chore(ci): parallelize checks and cache CDK Docker images

.projenrc.py

@@ -122,7 +122,28 @@
 pin_github_actions(gh)
 
 # Validate the CDK app offline on every pull request (no AWS credentials required)
-cdk_validate_workflow(gh, python_version, cdk_cli_version)
+cdk_validate_workflow(
+    gh,
+    python_version,
+    cdk_cli_version,
+    [env for env, account in target_accounts.items() if account],
+)
+
+# Temporary until actionlint supports background/wait steps (rhysd/actionlint#693).
+YamlFile(
+    project,
+    ".github/actionlint.yaml",
+    obj={
+        "paths": {
+            ".github/workflows/{cdk-validate,cdk-deploy-*}.yml": {
+                "ignore": [
+                    '^step must run script with "run" section or run action with "uses" section$',
+                    r'^unexpected key "background" for step to (run shell command|execute action)\. expected one of .+$',
+                ],
+            },
+        },
+    },
+)
 
 # Add Dependabot configuration for uv
 YamlFile(

src/bin/cicd_helper.py

@@ -5,6 +5,8 @@
 # render the same versions as the workflows built here.
 GITHUB_ACTIONS = {
     "checkout": "actions/checkout@v7",
+    "cache_restore": "actions/cache/restore@v6",
+    "cache_save": "actions/cache/save@v6",
     "configure_aws_credentials": "aws-actions/configure-aws-credentials@v6",
     "semantic_pull_request": "amannn/action-semantic-pull-request@v6",
     "setup_python": "actions/setup-python@v7",
@@ -18,7 +20,7 @@ def pin_github_actions(gh):
         gh.actions.set(action.split("@")[0], action)
 
 
-def cdk_environment_steps(python_version, cdk_cli_version):
+def cdk_environment_steps(python_version, cdk_cli_version, aws_credentials=None):
     """Checkout, Python, uv, project dependencies and the CDK CLI."""
     return [
         {
@@ -38,19 +40,85 @@ def cdk_environment_steps(python_version, cdk_cli_version):
             "name": "Setup uv",
             "uses": GITHUB_ACTIONS["setup_uv"],
         },
+        *([aws_credentials] if aws_credentials else []),
         {
             "name": "Install dependencies",
-            "run": "uv sync",
+            "run": "uv sync --frozen",
         },
         {
             "name": "Install cdk cli",
             "run": f"npm install -g aws-cdk@{cdk_cli_version}",
         },
+        *(
+            [
+                {
+                    "name": "Wait for AWS authentication",
+                    "wait": ["configure_aws_credentials"],
+                }
+            ]
+            if aws_credentials
+            else []
+        ),
     ]
 
 
-def cdk_validate_workflow(gh, python_version, cdk_cli_version):
+def docker_asset_cache_steps():
+    """Restore content-addressed bundling images; skip uploads for apps without Docker assets."""
+    cache_path = "${{ runner.temp }}/docker-assets"
+    cache_prefix = "docker-assets-v2-${{ runner.os }}-${{ runner.arch }}-${{ steps.docker_cache_epoch.outputs.week }}-"
+    restore = [
+        {
+            "name": "Choose Docker cache refresh week",
+            "id": "docker_cache_epoch",
+            "run": 'echo "week=$(date -u +%G-%V)" >> "$GITHUB_OUTPUT"\necho "source=$(git rev-parse "HEAD^{tree}")" >> "$GITHUB_OUTPUT"',
+        },
+        {
+            "name": "Restore Docker asset images",
+            "id": "docker_cache",
+            "uses": GITHUB_ACTIONS["cache_restore"],
+            "with": {
+                "path": cache_path,
+                "key": cache_prefix + "${{ steps.docker_cache_epoch.outputs.source }}",
+                "restore-keys": cache_prefix,
+            },
+        },
+        {
+            "name": "Load Docker asset images",
+            "run": 'if [ -f "$RUNNER_TEMP/docker-assets/images.tar" ]; then docker load --input "$RUNNER_TEMP/docker-assets/images.tar"; fi',
+        },
+    ]
+    save = [
+        {
+            "name": "Export Docker asset images",
+            "id": "export_docker_images",
+            "if": "steps.docker_cache.outputs.cache-hit != 'true'",
+            "shell": "bash",
+            "run": (
+                "images=()\n"
+                'while IFS= read -r image; do images+=("$image"); done < <(docker image ls --filter "reference=cdk-*" --format "{{.Repository}}:{{.Tag}}")\n'
+                'if [ "${#images[@]}" -gt 0 ]; then\n'
+                '  mkdir -p "$RUNNER_TEMP/docker-assets"\n'
+                '  docker save --output "$RUNNER_TEMP/docker-assets/images.tar" "${images[@]}"\n'
+                '  echo "has-images=true" >> "$GITHUB_OUTPUT"\n'
+                "fi"
+            ),
+        },
+        {
+            "name": "Save Docker asset images",
+            "if": "steps.export_docker_images.outputs.has-images == 'true'",
+            "uses": GITHUB_ACTIONS["cache_save"],
+            "with": {
+                "path": cache_path,
+                "key": "${{ steps.docker_cache.outputs.cache-primary-key }}",
+            },
+        },
+    ]
+    return restore, save
+
+
+def cdk_validate_workflow(gh, python_version, cdk_cli_version, environments):
     """Validate the CDK app offline on pull requests, without AWS credentials."""
+    restore_cache, save_cache = docker_asset_cache_steps()
     workflow = github.GithubWorkflow(gh, "cdk-validate")
     workflow.on(pull_request={}, workflow_dispatch={})
     workflow.add_jobs(
@@ -63,10 +131,30 @@ def cdk_validate_workflow(gh, python_version, cdk_cli_version):
                 },
                 "steps": [
                     *cdk_environment_steps(python_version, cdk_cli_version),
+                    *restore_cache,
+                    *[
+                        {
+                            "id": f"validate_{env}",
+                            "name": f"Validate {env} offline",
+                            "background": True,
+                            "run": f'uv run projen {env}:validate --no-online --output "${{{{ runner.temp }}}}/cdk-assemblies/{env}"',
+                        }
+                        for env in environments
+                    ],
                     {
-                        "name": "Validate CDK app against the default rule set",
-                        "run": "uv run projen validate",
+                        "id": "unit_tests",
+                        "name": "Run tests",
+                        "background": True,
+                        "run": "uv run projen test",
                     },
+                    {
+                        "name": "Wait for validation and tests",
+                        "wait": [
+                            *[f"validate_{env}" for env in environments],
+                            "unit_tests",
+                        ],
+                    },
+                    *save_cache,
                 ],
             },
         }
@@ -93,15 +181,20 @@ def github_cicd(gh, account, env, python_version, aws_region, cdk_cli_version):
                     "idToken": github.workflows.JobPermission.WRITE,
                 },
                 "steps": [
-                    *cdk_environment_steps(python_version, cdk_cli_version),
-                    {
-                        "name": "Configure AWS credentials",
-                        "uses": GITHUB_ACTIONS["configure_aws_credentials"],
-                        "with": {
-                            "role-to-assume": f"arn:aws:iam::{account}:role/GitHubDeployRole",
-                            "aws-region": aws_region,
+                    *cdk_environment_steps(
+                        python_version,
+                        cdk_cli_version,
+                        aws_credentials={
+                            "id": "configure_aws_credentials",
+                            "name": "Configure AWS credentials",
+                            "background": True,
+                            "uses": GITHUB_ACTIONS["configure_aws_credentials"],
+                            "with": {
+                                "role-to-assume": f"arn:aws:iam::{account}:role/GitHubDeployRole",
+                                "aws-region": aws_region,
+                            },
                         },
-                    },
+                    ),
                     {
                         "name": f"Validate CDK for the {env.upper()} environment",
                         "run": f"uv run projen {env}:validate",