fix: eliminate singleton registries and optimize scheduler async handling (fixes #1638)

src/praisonai/praisonai/_registry.py

@@ -0,0 +1,164 @@
+"""Generic plugin registry implementation for PraisonAI.
+
+This module provides a unified registry pattern to replace the divergent singleton
+implementations across the codebase. It supports both built-in and entry-point
+based plugin discovery with thread-safe registration and dependency injection.
+"""
+
+from __future__ import annotations
+
+import threading
+from importlib.metadata import entry_points
+from typing import Callable, Dict, Generic, Optional, Type, TypeVar
+import logging
+
+T = TypeVar("T")
+logger = logging.getLogger(__name__)
+
+
+class PluginRegistry(Generic[T]):
+    """Generic plugin registry: builtins + entry points + runtime register().
+
+    This replaces the singleton pattern with dependency injection while maintaining
+    the same functionality. Supports:
+    - Built-in plugins with lazy loading
+    - Entry points discovery
+    - Runtime registration
+    - Thread-safe operations
+    """
+
+    def __init__(
+        self, 
+        *,
+        entry_point_group: str,
+        builtins: Optional[Dict[str, Callable[[], Type[T]]]] = None
+    ) -> None:
+        """Initialize the registry.
+
+        Args:
+            entry_point_group: Entry points group name for plugin discovery
+            builtins: Dict of name -> loader function for built-in plugins
+        """
+        self._entry_point_group = entry_point_group
+        self._items: Dict[str, Type[T]] = {}
+        self._lock = threading.Lock()
+
+        # Load built-in plugins with error handling
+        if builtins:
+            for name, loader in builtins.items():
+                try:
+                    self._items[name] = loader()
+                except ImportError:
+                    # Built-in plugin dependencies not available, skip
+                    pass
+                except Exception:
+                    # Log other errors but don't crash initialization
+                    logger.warning("Failed to load built-in plugin %r", name, exc_info=True)
+
+        self._load_entry_points()
+
+    def _load_entry_points(self) -> None:
+        """Load plugins from entry points."""
+        try:
+            for ep in entry_points(group=self._entry_point_group):
+                try:
+                    plugin_class = ep.load()
+                    with self._lock:
+                        self._items[ep.name] = plugin_class
+                except Exception:
+                    # Do not break plugin dispatch because one plugin is broken
+                    logger.warning(
+                        "Failed to load plugin %r from entry point",
+                        ep.name,
+                        exc_info=True,
+                    )
+        except Exception:
+            # entry_points() might not be available in older Python versions
+            logger.debug("Entry points not available for group %s", self._entry_point_group)
+
+    def register(self, name: str, cls: Type[T]) -> None:
+        """Register a plugin at runtime.
+
+        Args:
+            name: Plugin name
+            cls: Plugin class
+        """
+        with self._lock:
+            self._items[name.lower()] = cls
+
+    def unregister(self, name: str) -> bool:
+        """Unregister a plugin.
+
+        Args:
+            name: Plugin name
+
+        Returns:
+            True if plugin was found and removed, False otherwise
+        """
+        with self._lock:
+            return self._items.pop(name.lower(), None) is not None
+
+    def resolve(self, name: str) -> Type[T]:
+        """Resolve a plugin name to its class.
+
+        Args:
+            name: Plugin name
+
+        Returns:
+            Plugin class
+
+        Raises:
+            ValueError: If plugin is not found
+        """
+        with self._lock:
+            cls = self._items.get(name.lower())
+            # Capture available plugins snapshot while holding lock
+            # to avoid race condition between check and error message
+            available_snapshot = sorted(self._items.keys()) if cls is None else None
+
+        if cls is None:
+            raise ValueError(
+                f"Unknown {self._entry_point_group} plugin: {name!r}. "
+                f"Available: {available_snapshot}"
+            )
+        return cls
+
+    def create(self, name: str, *args, **kwargs) -> T:
+        """Create an instance of the specified plugin.
+
+        Args:
+            name: Plugin name
+            *args, **kwargs: Arguments to pass to plugin constructor
+
+        Returns:
+            Plugin instance
+
+        Raises:
+            ValueError: If plugin is not found
+        """
+        cls = self.resolve(name)
+        return cls(*args, **kwargs)
+
+    def list_names(self) -> list[str]:
+        """List all registered plugin names.
+
+        Returns:
+            Sorted list of plugin names
+        """
+        with self._lock:
+            return sorted(self._items.keys())
+
+    def is_available(self, name: str) -> bool:
+        """Check if a plugin is available.
+
+        Args:
+            name: Plugin name
+
+        Returns:
+            True if plugin exists and can be created
+        """
+        try:
+            self.resolve(name)
+            return True
+        except ValueError:
+            return False

src/praisonai/praisonai/agents_generator.py

@@ -19,7 +19,7 @@
 
 # Import new architecture components
 from .framework_adapters.base import FrameworkAdapter
-from .framework_adapters.registry import FrameworkAdapterRegistry
+from .framework_adapters.registry import FrameworkAdapterRegistry, get_default_registry
 from .tool_registry import ToolRegistry
 
 # Import availability flags
@@ -179,7 +179,7 @@ def _resolve_yaml_cli_backend(cli_backend_config, logger):
 
 
 class AgentsGenerator:
-    def __init__(self, agent_file, framework, config_list, log_level=None, agent_callback=None, task_callback=None, agent_yaml=None, tools=None, cli_config=None):
+    def __init__(self, agent_file, framework, config_list, log_level=None, agent_callback=None, task_callback=None, agent_yaml=None, tools=None, cli_config=None, adapter_registry=None):
         """
         Initialize the AgentsGenerator object.
 
@@ -193,6 +193,7 @@ def __init__(self, agent_file, framework, config_list, log_level=None, agent_cal
             agent_yaml (str, optional): The content of the YAML file. Defaults to None.
             tools (dict, optional): A dictionary containing the tools to be used for the agents. Defaults to None.
             cli_config (dict, optional): CLI configuration to override YAML settings. Defaults to None.
+            adapter_registry (FrameworkAdapterRegistry, optional): Registry for framework adapters. Defaults to process default.
 
         Attributes:
             agent_file (str): The path to the agent file.
@@ -233,6 +234,10 @@ def __init__(self, agent_file, framework, config_list, log_level=None, agent_cal
         self.tool_registry = ToolRegistry()
         self.tool_registry.register_builtin_autogen_adapters()
 
+        # DI-friendly: tests/multi-tenant runtimes pass their own registry;
+        # CLI users get the process default.
+        self._adapter_registry = adapter_registry or get_default_registry()
+
         # Get framework adapter (availability already validated at CLI entry)
         self.framework_adapter = self._get_framework_adapter(framework)
 
@@ -249,8 +254,7 @@ def _get_framework_adapter(self, framework: str) -> FrameworkAdapter:
         Raises:
             ValueError: If framework is not supported
         """
-        adapter_registry = FrameworkAdapterRegistry.get_instance()
-        return adapter_registry.create(framework)
+        return self._adapter_registry.create(framework)
 
     def _merge_cli_config(self, config, cli_config):
         """

src/praisonai/praisonai/auto.py

@@ -628,7 +628,8 @@ class AutoGenerator(BaseAutoGenerator):
 
     def __init__(self, topic="Movie Story writing about AI", agent_file="test.yaml", 
                  framework="crewai", config_list: Optional[List[Dict]] = None,
-                 pattern: str = "sequential", single_agent: bool = False):
+                 pattern: str = "sequential", single_agent: bool = False, 
+                 adapter_registry=None):
         """
         Initialize the AutoGenerator class with the specified topic, agent file, and framework.
 
@@ -646,15 +647,15 @@ def __init__(self, topic="Movie Story writing about AI", agent_file="test.yaml",
         super().__init__(config_list=config_list)
 
         # Validate framework availability using adapter registry
-        from .framework_adapters.registry import FrameworkAdapterRegistry
+        from .framework_adapters.registry import get_default_registry
 
-        registry = FrameworkAdapterRegistry.get_instance()
+        self._adapter_registry = adapter_registry or get_default_registry()
         try:
-            adapter = registry.create(framework)
+            adapter = self._adapter_registry.create(framework)
         except ValueError as e:
             raise ImportError(
                 f"Unknown framework '{framework}'. Available frameworks: "
-                f"{', '.join(registry.list_registered())}"
+                f"{', '.join(self._adapter_registry.list_registered())}"
             ) from e
 
         # Use safe fallbacks for new adapter attributes