Added support for storage backend and event handler plugins

Signed-off-by: Christian Pinto <christian.pinto@ibm.com>

.gitignore

@@ -8,3 +8,8 @@ tests/.pytest_cache
 # Remove directory __pycache__
 __pycache__
 venv
+
+.idea
+build
+sunfish.egg-info
+

pyproject.toml

@@ -5,9 +5,14 @@ description = ""
 authors = ["Erika Rosaverde <erika.rosaverde@ibm.com>"]
 readme = "README.md"
 packages = [
-	{ include = "sunfish" }
+	{ include = "sunfish" },
+	{ include = "sunfish_plugins", from = "." }
 ]
 
+[tool.setuptools.packages.find]
+where = ["."]
+include = ["sunfish_plugins.*"]
+
 [tool.poetry.dependencies]
 python = ">=3.9"
 flask = "^2.3.3"

sunfish/lib/core.py

@@ -8,15 +8,14 @@
 import logging
 from typing import Optional
 
-from sunfish.storage.backend_FS import BackendFS
 from sunfish.lib.exceptions import CollectionNotSupported, ResourceNotFound, AgentForwardingFailure, PropertyNotFound
-from sunfish.events.redfish_event_handler import RedfishEventHandler, RedfishEventHandlersTable
+from sunfish_plugins.event_handlers.redfish.redfish_event_handler import RedfishEventHandler
 
 from sunfish.events.redfish_subscription_handler import RedfishSubscriptionHandler
 from sunfish.lib.object_handler import RedfishObjectHandler
 from sunfish.models.types import *
 from sunfish.lib.agents_management import Agent
-
+import sunfish.models.plugins as plugin_modules
 logger = logging.getLogger(__name__)
 
 
@@ -31,17 +30,62 @@ def __init__(self, conf):
 
         self.conf = conf
 
-        if conf['storage_backend'] == 'FS':
-            self.storage_backend = BackendFS(self.conf)
-        # elif conf['storage_backend'] == '<OTHER STORAGE>':
-        # ...
+        # The Sunfish core library uses a plugin mechanism that allows dynamic loading of certain classes. This helps
+        # users with updating the behavior of the sunfish library without having to modify its core classes.
+        # At the moment we support plugins for the storage backend and for the redfish event handlers.
+        # Plugins are implemented as namespaced packages and must be placed in a folder at the top of the project named
+        # "sunfish_plugins", with subfolders named "storage" and/or "event_handlers". The python packages defined inside
+        # each subfolder are totally user defined.
+        # ── sunfish_plugins
+        #    ├── storage
+        #    │   └──my_storage_package     <--- User defined
+        #    │      ├── __init__.py
+        #    │      └── my_storage_backend.py
+        #    └── event_handlers
+        #        └──my_handler_package     <--- User defined
+        #           ├── __init__.py
+        #           └── my_handler.py
+
+        # When initializing the Sunfish libraries can load their storage or event handler plugin by specifying them in
+        # the configuration as in the below example:
+        #
+        # "storage_backend" : {
+        #         "module_name": "storage.my_storage_package.my_storage_backend",
+        #         "class_name": "StorageBackend"
+        # },
+        # "event_backend" : {
+        #         "module_name": "event-handlers.my_handler_package.my_handler",
+        #         "class_name": "StorageBackend"
+        # },
+        #
+        # In both cases "class_name" represents the name of the class that is initialized and implements the respective
+        # interface.
+
+        # Default storage plugin loaded if nothing is specified in the configuration
+        if not "storage_backend" in conf:
+            storage_plugin = {
+                "module_name": "storage.file_system_backend.backend_FS",
+                "class_name": "BackendFS"
+            }
+        else:
+            storage_plugin = conf["storage_backend"]
+        storage_cl = plugin_modules.load_plugin(storage_plugin)
+        self.storage_backend = storage_cl(self.conf)
+
+        # Default event_handler plugin loaded if nothing is specified in the configuration
+        if not "event_handler" in conf:
+            event_plugin = {
+                "module_name": "event_handlers.redfish.redfish_event_handler",
+                "class_name": "RedfishEventHandler"
+            }
+        else:
+            event_plugin = conf["event_handler"]
+        event_cl = plugin_modules.load_plugin(event_plugin)
+        self.event_handler = event_cl(self)
 
         if conf['handlers']['subscription_handler'] == 'redfish':
             self.subscription_handler = RedfishSubscriptionHandler(self)
 
-        if conf['handlers']['event_handler'] == 'redfish':
-            self.event_handler = RedfishEventHandler(self)
-
     def get_object(self, path: string):
         """Calls the correspondent read function from the backend implementation and checks that the path is valid.
 

sunfish/models/plugins.py

@@ -0,0 +1,19 @@
+# Copyright IBM Corp. 2024
+# This software is available to you under a BSD 3-Clause License.
+# The full license terms are available here: https://github.com/OpenFabrics/sunfish_library_reference/blob/main/LICENSE
+
+import importlib
+import logging
+
+logger = logging.getLogger(__name__)
+
+plugins_namespace_name = "sunfish_plugins"
+
+
+def load_plugin(plugin: dict):
+    module_name = f"{plugins_namespace_name}.{plugin['module_name']}"
+    logger.info(f"Loading plugin {module_name}...")
+    plugin_module = importlib.import_module(module_name)
+    logger.info("Plugin loaded")
+    return getattr(plugin_module, plugin["class_name"])
+

sunfish/events/redfish_event_handler.py → sunfish_plugins/event_handlers/redfish/redfish_event_handler.py

@@ -4,7 +4,6 @@
 import json
 import logging
 import os
-from uuid import uuid4
 import warnings
 
 import requests

sunfish/storage/backend_FS.py → sunfish_plugins/storage/file_system_backend/backend_FS.py

@@ -8,7 +8,7 @@
 import shutil
 
 from sunfish.storage.backend_interface import BackendInterface
-from sunfish.storage import utils
+from sunfish_plugins.storage.file_system_backend import utils
 from sunfish.lib.exceptions import *
 
 logger = logging.getLogger(__name__)

tests/conf.json

@@ -1,10 +1,17 @@
 {
-    "storage_backend": "FS",
     "redfish_root": "/redfish/v1/",
+    "storage_backend": {
+        "module_name": "storage.file_system_backend.backend_FS",
+        "class_name": "BackendFS"
+    },
     "backend_conf" : {
         "fs_root": "Resources",
         "subscribers_root": "EventService/Subscriptions"
     },
+    "event_handler": {
+        "module_name": "event_handlers.redfish.redfish_event_handler",
+        "class_name": "RedfishEventHandler"
+    },
     "handlers": {
         "subscription_handler": "redfish",
         "event_handler": "redfish"

tests/test_sunfishcore_library.py

@@ -6,15 +6,12 @@
 # from http.server import BaseHTTPRequestHandler
 import json
 import os
-import shutil
 import logging
 import pytest
-import requests
 from pytest_httpserver import HTTPServer
 from sunfish.lib.core import Core
 from sunfish.lib.exceptions import *
 from tests import test_utils, tests_template
-
 class TestSunfishcoreLibrary():
     @classmethod
     def setup_class(cls):
@@ -27,6 +24,17 @@ def setup_class(cls):
 
         cls.core = Core(cls.conf)
 
+    @pytest.mark.order("first")
+    def test_init_core(self):
+        path = os.path.join(os.getcwd(), 'tests', 'conf.json')
+        try:
+            json_data = open(path)
+            conf = json.load(json_data)
+        except FileNotFoundError as e:
+            raise ResourceNotFound('conf.json')
+
+        core = Core(conf)
+
     # TEST REST
     # Delete
     @pytest.mark.order("last")