[misc][plugin] add plugin system implementation (#7426)

vllm/plugins/__init__.py

@@ -0,0 +1,31 @@
+import logging
+
+import vllm.envs as envs
+
+logger = logging.getLogger(__name__)
+
+
+def load_general_plugins():
+    """WARNING: plugins can be loaded for multiple times in different
+    processes. They should be designed in a way that they can be loaded
+    multiple times without causing issues.
+    """
+    import sys
+    if sys.version_info < (3, 10):
+        from importlib_metadata import entry_points
+    else:
+        from importlib.metadata import entry_points
+
+    allowed_plugins = envs.VLLM_PLUGINS
+
+    discovered_plugins = entry_points(group='vllm.general_plugins')
+    for plugin in discovered_plugins:
+        logger.info("Found general plugin: %s", plugin.name)
+        if allowed_plugins is None or plugin.name in allowed_plugins:
+            try:
+                func = plugin.load()
+                func()
+                logger.info("Loaded general plugin: %s", plugin.name)
+            except Exception:
+                logger.exception("Failed to load general plugin: %s",
+                                 plugin.name)