[Nexthop] Add component system for FBOSS Image Builder

Add abstract build component framework for managing build operations.

- Implement AbstractComponent base class for build components
- Add component lifecycle management (prepare, build, extract)
- Integrate with artifact store, download, and execute modules
- Enable extensible component-based build architecture

Tests utilizing the above infrastructure will be added when component build supports are included.

Author: raghav-nexthop

fboss-image/distro_cli/builder/component.py

@@ -0,0 +1,343 @@
+# Copyright (c) 2004-present, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree. An additional grant
+# of patent rights can be found in the PATENTS file in the same directory.
+
+"""Generic component builder for FBOSS image components."""
+
+import hashlib
+import logging
+from os.path import commonpath
+from pathlib import Path
+
+from distro_cli.lib.artifact import find_artifact_in_dir
+from distro_cli.lib.constants import FBOSS_BUILDER_IMAGE
+from distro_cli.lib.download import download_artifact
+from distro_cli.lib.exceptions import ComponentError
+from distro_cli.lib.execute import execute_build_in_container
+from distro_cli.lib.paths import get_abs_path
+
+logger = logging.getLogger(__name__)
+
+
+def _get_component_directory(component_name: str, script_path: str) -> str:
+    """Determine the component directory for build artifacts.
+
+    For scripts_path that has the component_name, we return the path in script_path
+    leading to the component_name. Otherwise, the script's parent directory is returned.
+
+    Examples:
+        kernel component:
+            component_name="kernel"
+            script_path="fboss-image/kernel/scripts/build_kernel.sh"
+            returns: "fboss-image/kernel" (component_name found in path)
+
+        sai component:
+            component_name="sai"
+            script_path="broadcom-sai-sdk/build_fboss_sai.sh"
+            returns: "broadcom-sai-sdk" (fallback to script's parent)
+
+    Args:
+        component_name: Base component name (without array index)
+        script_path: Path to the build script from the execute directive
+
+    Returns:
+        Component directory path (relative to workspace root)
+
+    """
+    script_path_obj = Path(script_path)
+
+    # Check if component_name appears in the script path
+    if component_name in script_path_obj.parts:
+        # Find the last occurrence of component_name in the path
+        # Handle cases where component name appears multiple times
+        # e.g., /src/kernel/fboss/12345/kernel/build.sh -> use the last "kernel"
+        parts = script_path_obj.parts
+        # Find last occurrence by reversing and using index
+        component_index = len(parts) - 1 - parts[::-1].index(component_name)
+        # Return the path up to and including the component_name
+        return str(Path(*parts[: component_index + 1]))
+
+    # Fall back to script's parent directory
+    return str(script_path_obj.parent)
+
+
+class ComponentBuilder:
+    """Generic builder for FBOSS image components.
+
+    Supports two modes:
+    - download: Download pre-built artifact from URL
+    - execute: Build component using a build script in Docker container
+
+    Component-specific logic (argument parsing, paths, etc.) should be
+    embedded in the component build script, not in this builder.
+    """
+
+    def __init__(
+        self,
+        component_name: str,
+        component_data: dict,
+        manifest_dir: Path,
+        store,
+        artifact_pattern: str | None = None,
+        dependency_artifacts: dict[str, Path] | None = None,
+        artifact_key_salt: str | None = None,
+    ):
+        """Initialize the component builder.
+
+        Args:
+            component_name: Name of the component
+            component_data: Component data dict from manifest
+            manifest_dir: Path to the manifest directory
+            store: ArtifactStore instance
+            artifact_pattern: Glob pattern for finding build artifacts (e.g., "kernel-*.rpms.tar.zst")
+                             If None, component cannot use execute mode
+            dependency_artifacts: Optional dict mapping dependency names to their artifact paths
+            artifact_key_salt: Salt added to artifact store key to differentiate variants
+        """
+        self.component_name = component_name
+        self.component_data = component_data
+        self.manifest_dir = manifest_dir
+        self.store = store
+        self.artifact_pattern = artifact_pattern
+        self.dependency_artifacts = dependency_artifacts or {}
+        self.artifact_key_salt = artifact_key_salt
+
+    def build(self) -> Path:
+        """Build or download the component.
+
+        Returns:
+            Path to the component artifact (or None for empty components)
+
+        Raises:
+            ComponentError: If component has invalid structure
+        """
+        if self.component_data is None:
+            raise ComponentError(f"Component '{self.component_name}' has no data")
+
+        # ComponentBuilder handles single component instances only
+        # Array components should be handled at a higher level (e.g., ImageBuilder)
+        # by creating one ComponentBuilder instance per array element
+        if isinstance(self.component_data, list):
+            raise ComponentError(
+                f"Component '{self.component_name}' data is an array. "
+                "ComponentBuilder only handles single component instances. "
+                "Create one ComponentBuilder per array element instead."
+            )
+
+        # Check for both download and execute (invalid)
+        has_download = "download" in self.component_data
+        has_execute = "execute" in self.component_data
+
+        if has_download and has_execute:
+            raise ComponentError(
+                f"Component '{self.component_name}' has both 'download' and 'execute' fields. "
+                "Only one is allowed."
+            )
+
+        # Allow empty components
+        if not has_download and not has_execute:
+            logger.info(f"Component '{self.component_name}' is empty, skipping")
+            return None
+
+        if has_download:
+            return self._download_component(self.component_data["download"])
+
+        # this must be an "execute"
+        # Use artifact pattern from manifest if specified, otherwise use default
+        artifact_pattern = self.component_data.get("artifact", self.artifact_pattern)
+        return self._execute_component(self.component_data["execute"], artifact_pattern)
+
+    def _download_component(self, url: str) -> Path:
+        """Download component artifact from URL.
+
+        Args:
+            url: URL to download from
+
+        Returns:
+            Path to downloaded artifact (cached)
+        """
+        store_key = (
+            f"{self.component_name}-download-{hashlib.sha256(url.encode()).hexdigest()}"
+        )
+        data_files, metadata_files = self.store.get(
+            store_key,
+            lambda data, meta: download_artifact(url, self.manifest_dir, data, meta),
+        )
+
+        if not data_files:
+            raise ComponentError(f"No artifact files found for {self.component_name}")
+
+        artifact_path = data_files[0]
+        logger.info(f"{self.component_name} artifact ready: {artifact_path}")
+        if metadata_files:
+            logger.debug(f"  with {len(metadata_files)} metadata file(s)")
+        return artifact_path
+
+    def _execute_component(
+        self, cmd_line: str | list[str], artifact_pattern: str | None = None
+    ) -> Path:
+        """Execute component build in Docker container.
+
+        Args:
+            cmd_line: Command line to execute (string or list of strings)
+            artifact_pattern: Optional artifact pattern override from manifest
+
+        Returns:
+            Path to build artifact in cache
+        """
+        # For store key, convert to string (works for both str and list)
+        # Include artifact_key_salt to differentiate cache variants (e.g., compressed vs uncompressed)
+        store_key_str = f"{cmd_line}-salt={self.artifact_key_salt}"
+
+        # _execute_build as a fetch_fn always starts a build expecting the underlying
+        # build system to provide build specific optimizations. The objects are returned
+        # back to the store with a store-miss indication.
+        store_key = f"{self.component_name}-build-{hashlib.sha256(store_key_str.encode()).hexdigest()[:8]}"
+        data_files, _ = self.store.get(
+            store_key,
+            lambda _data, _meta: (
+                False,
+                [self._execute_build(cmd_line, artifact_pattern)],
+                [],
+            ),
+        )
+
+        if not data_files:
+            raise ComponentError(f"No artifact files found for {self.component_name}")
+
+        artifact_path = data_files[0]
+        logger.info(f"{self.component_name} build complete: {artifact_path}")
+        return artifact_path
+
+    def _execute_build(
+        self, cmd_line: str | list[str], artifact_pattern: str | None = None
+    ) -> Path:
+        """Execute build in Docker container.
+
+        Args:
+            cmd_line: Command line to execute (string or list of strings)
+            artifact_pattern: Optional artifact pattern override from manifest
+
+        Returns:
+            Path to build artifact
+
+        Raises:
+            ComponentError: If build fails or artifact not found
+        """
+        # Get script path from command line
+        script_path_str = (
+            cmd_line[0] if isinstance(cmd_line, list) else cmd_line.split()[0]
+        )
+
+        # Resolve script path: if absolute, use as-is; if relative, resolve from manifest_dir
+        script_path = Path(script_path_str)
+        resolved_script_path = (
+            script_path
+            if script_path.is_absolute()
+            else (self.manifest_dir / script_path).resolve()
+        )
+
+        # Verify the script exists
+        if not resolved_script_path.exists():
+            raise ComponentError(
+                f"Build script not found: {resolved_script_path} "
+                f"(from manifest path: {script_path_str})"
+            )
+
+        # We mount the common parent of the script path and manifest dir
+        src_dir = Path(commonpath([resolved_script_path, self.manifest_dir]))
+        script_relative_to_src = resolved_script_path.relative_to(src_dir)
+        container_script_path = Path("/src") / script_relative_to_src
+
+        # For array elements, extract the base name
+        base_name = (
+            self.component_name.split("[")[0]
+            if "[" in self.component_name
+            else self.component_name
+        )
+
+        # Determine component directory (component root if known, else script's parent)
+        # Use the resolved script path relative to src_dir
+        script_relative_to_src = resolved_script_path.relative_to(src_dir)
+        component_dir = _get_component_directory(base_name, str(script_relative_to_src))
+
+        # Create build and dist directories under the component directory
+        artifact_base_dir = src_dir / component_dir
+
+        # Use artifact_pattern from parameter, or fall back to instance pattern, or use generic pattern
+        # Generic pattern uses .tar (will match both .tar and .tar.zst via compression variant finder)
+        if artifact_pattern is None:
+            artifact_pattern = self.artifact_pattern or "*.tar"
+        if not artifact_pattern:
+            logger.warning(
+                f"Component '{self.component_name}' has no artifact_pattern specified. "
+                f"Using generic pattern: {artifact_pattern}"
+            )
+
+        build_dir = artifact_base_dir / ".build"
+        build_dir.mkdir(parents=True, exist_ok=True)
+
+        dist_dir = artifact_base_dir / "dist"
+        dist_dir.mkdir(parents=True, exist_ok=True)
+
+        # Mount src_dir as /src in the container
+        logger.info(f"Mounting {src_dir} as /src")
+
+        # Mount distro_cli/tools as /tools for build utilities
+        tools_dir = get_abs_path("fboss-image/distro_cli/tools")
+
+        # Mount fboss/oss/scripts for common build utilities (sccache config, etc.)
+        common_scripts_dir = get_abs_path("fboss/oss/scripts")
+
+        volumes = {
+            src_dir: Path("/src"),
+            build_dir: Path("/build"),
+            dist_dir: Path("/output"),
+            tools_dir: Path("/tools"),
+            common_scripts_dir: Path("/fboss/oss/scripts"),
+        }
+
+        # Mount dependency artifacts into the container
+        dependency_install_paths = {}
+        for dep_name, dep_artifact in self.dependency_artifacts.items():
+            dep_mount_point = Path(f"/deps/{dep_name}")
+            volumes[dep_artifact] = dep_mount_point
+            dependency_install_paths[dep_name] = dep_mount_point
+            logger.info(
+                f"Mounting dependency '{dep_name}' at {dep_mount_point}: {dep_artifact}"
+            )
+
+        # Working directory is the parent of the script
+        working_dir = str(container_script_path.parent)
+
+        # Build the container command using the container script path
+        if isinstance(cmd_line, list):
+            # Replace first element with container path, keep the rest
+            container_cmd = [str(container_script_path), *cmd_line[1:]]
+        else:
+            # For string commands, replace the script path with the in-container version
+            container_cmd = [str(container_script_path)]
+
+        logger.info(f"Container command: {container_cmd}")
+
+        # Execute build command
+        execute_build_in_container(
+            image_name=FBOSS_BUILDER_IMAGE,
+            command=container_cmd,
+            volumes=volumes,
+            component_name=self.component_name,
+            privileged=False,
+            working_dir=working_dir,
+            dependency_install_paths=(
+                dependency_install_paths if dependency_install_paths else None
+            ),
+        )
+
+        return find_artifact_in_dir(
+            output_dir=dist_dir,
+            pattern=artifact_pattern,
+            component_name=self.component_name.capitalize(),
+        )