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"""Directed Graph Multi-Agent Pattern Implementation.
This module provides a deterministic graph-based agent orchestration system where
agents or MultiAgentBase instances (like Swarm or Graph) are nodes in a graph,
executed according to edge dependencies, with output from one node passed as input
to connected nodes.
Key Features:
- Agents and MultiAgentBase instances (Swarm, Graph, etc.) as graph nodes
- Deterministic execution based on dependency resolution
- Output propagation along edges
- Support for cyclic graphs (feedback loops)
- Clear dependency management
- Supports nested graphs (Graph as a node in another Graph)
"""
import asyncio
import copy
import logging
import time
from concurrent.futures import ThreadPoolExecutor
from dataclasses import dataclass, field
from typing import Any, Callable, Optional, Tuple
from opentelemetry import trace as trace_api
from ..agent import Agent
from ..agent.state import AgentState
from ..telemetry import get_tracer
from ..types.content import ContentBlock, Messages
from ..types.event_loop import Metrics, Usage
from .base import MultiAgentBase, MultiAgentResult, NodeResult, Status
logger = logging.getLogger(__name__)
@dataclass
class GraphState:
"""Graph execution state.
Attributes:
status: Current execution status of the graph.
completed_nodes: Set of nodes that have completed execution.
failed_nodes: Set of nodes that failed during execution.
execution_order: List of nodes in the order they were executed.
task: The original input prompt/query provided to the graph execution.
This represents the actual work to be performed by the graph as a whole.
Entry point nodes receive this task as their input if they have no dependencies.
"""
# Task (with default empty string)
task: str | list[ContentBlock] = ""
# Execution state
status: Status = Status.PENDING
completed_nodes: set["GraphNode"] = field(default_factory=set)
failed_nodes: set["GraphNode"] = field(default_factory=set)
execution_order: list["GraphNode"] = field(default_factory=list)
start_time: float = field(default_factory=time.time)
# Results
results: dict[str, NodeResult] = field(default_factory=dict)
# Accumulated metrics
accumulated_usage: Usage = field(default_factory=lambda: Usage(inputTokens=0, outputTokens=0, totalTokens=0))
accumulated_metrics: Metrics = field(default_factory=lambda: Metrics(latencyMs=0))
execution_count: int = 0
execution_time: int = 0
# Graph structure info
total_nodes: int = 0
edges: list[Tuple["GraphNode", "GraphNode"]] = field(default_factory=list)
entry_points: list["GraphNode"] = field(default_factory=list)
def should_continue(
self,
max_node_executions: Optional[int],
execution_timeout: Optional[float],
) -> Tuple[bool, str]:
"""Check if the graph should continue execution.
Returns: (should_continue, reason)
"""
# Check node execution limit (only if set)
if max_node_executions is not None and len(self.execution_order) >= max_node_executions:
return False, f"Max node executions reached: {max_node_executions}"
# Check timeout (only if set)
if execution_timeout is not None:
elapsed = time.time() - self.start_time
if elapsed > execution_timeout:
return False, f"Execution timed out: {execution_timeout}s"
return True, "Continuing"
@dataclass
class GraphResult(MultiAgentResult):
"""Result from graph execution - extends MultiAgentResult with graph-specific details."""
total_nodes: int = 0
completed_nodes: int = 0
failed_nodes: int = 0
execution_order: list["GraphNode"] = field(default_factory=list)
edges: list[Tuple["GraphNode", "GraphNode"]] = field(default_factory=list)
entry_points: list["GraphNode"] = field(default_factory=list)
@dataclass
class GraphEdge:
"""Represents an edge in the graph with an optional condition."""
from_node: "GraphNode"
to_node: "GraphNode"
condition: Callable[[GraphState], bool] | None = None
def __hash__(self) -> int:
"""Return hash for GraphEdge based on from_node and to_node."""
return hash((self.from_node.node_id, self.to_node.node_id))
def should_traverse(self, state: GraphState) -> bool:
"""Check if this edge should be traversed based on condition."""
if self.condition is None:
return True
return self.condition(state)
@dataclass
class GraphNode:
"""Represents a node in the graph.
The execution_status tracks the node's lifecycle within graph orchestration:
- PENDING: Node hasn't started executing yet
- EXECUTING: Node is currently running
- COMPLETED/FAILED: Node finished executing (regardless of result quality)
"""
node_id: str
executor: Agent | MultiAgentBase
dependencies: set["GraphNode"] = field(default_factory=set)
execution_status: Status = Status.PENDING
result: NodeResult | None = None
execution_time: int = 0
_initial_messages: Messages = field(default_factory=list, init=False)
_initial_state: AgentState = field(default_factory=AgentState, init=False)
def __post_init__(self) -> None:
"""Capture initial executor state after initialization."""
# Deep copy the initial messages and state to preserve them
if hasattr(self.executor, "messages"):
self._initial_messages = copy.deepcopy(self.executor.messages)
if hasattr(self.executor, "state") and hasattr(self.executor.state, "get"):
self._initial_state = AgentState(self.executor.state.get())
def reset_executor_state(self) -> None:
"""Reset GraphNode executor state to initial state when graph was created.
This is useful when nodes are executed multiple times and need to start
fresh on each execution, providing stateless behavior.
"""
if hasattr(self.executor, "messages"):
self.executor.messages = copy.deepcopy(self._initial_messages)
if hasattr(self.executor, "state"):
self.executor.state = AgentState(self._initial_state.get())
# Reset execution status
self.execution_status = Status.PENDING
self.result = None
def __hash__(self) -> int:
"""Return hash for GraphNode based on node_id."""
return hash(self.node_id)
def __eq__(self, other: Any) -> bool:
"""Return equality for GraphNode based on node_id."""
if not isinstance(other, GraphNode):
return False
return self.node_id == other.node_id
def _validate_node_executor(
executor: Agent | MultiAgentBase, existing_nodes: dict[str, GraphNode] | None = None
) -> None:
"""Validate a node executor for graph compatibility.
Args:
executor: The executor to validate
existing_nodes: Optional dict of existing nodes to check for duplicates
"""
# Check for duplicate node instances
if existing_nodes:
seen_instances = {id(node.executor) for node in existing_nodes.values()}
if id(executor) in seen_instances:
raise ValueError("Duplicate node instance detected. Each node must have a unique object instance.")
# Validate Agent-specific constraints
if isinstance(executor, Agent):
# Check for session persistence
if executor._session_manager is not None:
raise ValueError("Session persistence is not supported for Graph agents yet.")
class GraphBuilder:
"""Builder pattern for constructing graphs."""
def __init__(self) -> None:
"""Initialize GraphBuilder with empty collections."""
self.nodes: dict[str, GraphNode] = {}
self.edges: set[GraphEdge] = set()
self.entry_points: set[GraphNode] = set()
# Configuration options
self._max_node_executions: Optional[int] = None
self._execution_timeout: Optional[float] = None
self._node_timeout: Optional[float] = None
self._reset_on_revisit: bool = False
def add_node(self, executor: Agent | MultiAgentBase, node_id: str | None = None) -> GraphNode:
"""Add an Agent or MultiAgentBase instance as a node to the graph."""
_validate_node_executor(executor, self.nodes)
# Auto-generate node_id if not provided
if node_id is None:
node_id = getattr(executor, "id", None) or getattr(executor, "name", None) or f"node_{len(self.nodes)}"
if node_id in self.nodes:
raise ValueError(f"Node '{node_id}' already exists")
node = GraphNode(node_id=node_id, executor=executor)
self.nodes[node_id] = node
return node
def add_edge(
self,
from_node: str | GraphNode,
to_node: str | GraphNode,
condition: Callable[[GraphState], bool] | None = None,
) -> GraphEdge:
"""Add an edge between two nodes with optional condition function that receives full GraphState."""
def resolve_node(node: str | GraphNode, node_type: str) -> GraphNode:
if isinstance(node, str):
if node not in self.nodes:
raise ValueError(f"{node_type} node '{node}' not found")
return self.nodes[node]
else:
if node not in self.nodes.values():
raise ValueError(f"{node_type} node object has not been added to the graph, use graph.add_node")
return node
from_node_obj = resolve_node(from_node, "Source")
to_node_obj = resolve_node(to_node, "Target")
# Add edge and update dependencies
edge = GraphEdge(from_node=from_node_obj, to_node=to_node_obj, condition=condition)
self.edges.add(edge)
to_node_obj.dependencies.add(from_node_obj)
return edge
def set_entry_point(self, node_id: str) -> "GraphBuilder":
"""Set a node as an entry point for graph execution."""
if node_id not in self.nodes:
raise ValueError(f"Node '{node_id}' not found")
self.entry_points.add(self.nodes[node_id])
return self
def reset_on_revisit(self, enabled: bool = True) -> "GraphBuilder":
"""Control whether nodes reset their state when revisited.
When enabled, nodes will reset their messages and state to initial values
each time they are revisited (re-executed). This is useful for stateless
behavior where nodes should start fresh on each revisit.
Args:
enabled: Whether to reset node state when revisited (default: True)
"""
self._reset_on_revisit = enabled
return self
def set_max_node_executions(self, max_executions: int) -> "GraphBuilder":
"""Set maximum number of node executions allowed.
Args:
max_executions: Maximum total node executions (None for no limit)
"""
self._max_node_executions = max_executions
return self
def set_execution_timeout(self, timeout: float) -> "GraphBuilder":
"""Set total execution timeout.
Args:
timeout: Total execution timeout in seconds (None for no limit)
"""
self._execution_timeout = timeout
return self
def set_node_timeout(self, timeout: float) -> "GraphBuilder":
"""Set individual node execution timeout.
Args:
timeout: Individual node timeout in seconds (None for no limit)
"""
self._node_timeout = timeout
return self
def build(self) -> "Graph":
"""Build and validate the graph with configured settings."""
if not self.nodes:
raise ValueError("Graph must contain at least one node")
# Auto-detect entry points if none specified
if not self.entry_points:
self.entry_points = {node for node_id, node in self.nodes.items() if not node.dependencies}
logger.debug(
"entry_points=<%s> | auto-detected entrypoints", ", ".join(node.node_id for node in self.entry_points)
)
if not self.entry_points:
raise ValueError("No entry points found - all nodes have dependencies")
# Validate entry points and check for cycles
self._validate_graph()
return Graph(
nodes=self.nodes.copy(),
edges=self.edges.copy(),
entry_points=self.entry_points.copy(),
max_node_executions=self._max_node_executions,
execution_timeout=self._execution_timeout,
node_timeout=self._node_timeout,
reset_on_revisit=self._reset_on_revisit,
)
def _validate_graph(self) -> None:
"""Validate graph structure."""
# Validate entry points exist
entry_point_ids = {node.node_id for node in self.entry_points}
invalid_entries = entry_point_ids - set(self.nodes.keys())
if invalid_entries:
raise ValueError(f"Entry points not found in nodes: {invalid_entries}")
# Warn about potential infinite loops if no execution limits are set
if self._max_node_executions is None and self._execution_timeout is None:
logger.warning("Graph without execution limits may run indefinitely if cycles exist")
class Graph(MultiAgentBase):
"""Directed Graph multi-agent orchestration with configurable revisit behavior."""
def __init__(
self,
nodes: dict[str, GraphNode],
edges: set[GraphEdge],
entry_points: set[GraphNode],
max_node_executions: Optional[int] = None,
execution_timeout: Optional[float] = None,
node_timeout: Optional[float] = None,
reset_on_revisit: bool = False,
) -> None:
"""Initialize Graph with execution limits and reset behavior.
Args:
nodes: Dictionary of node_id to GraphNode
edges: Set of GraphEdge objects
entry_points: Set of GraphNode objects that are entry points
max_node_executions: Maximum total node executions (default: None - no limit)
execution_timeout: Total execution timeout in seconds (default: None - no limit)
node_timeout: Individual node timeout in seconds (default: None - no limit)
reset_on_revisit: Whether to reset node state when revisited (default: False)
"""
super().__init__()
# Validate nodes for duplicate instances
self._validate_graph(nodes)
self.nodes = nodes
self.edges = edges
self.entry_points = entry_points
self.max_node_executions = max_node_executions
self.execution_timeout = execution_timeout
self.node_timeout = node_timeout
self.reset_on_revisit = reset_on_revisit
self.state = GraphState()
self.tracer = get_tracer()
def __call__(
self, task: str | list[ContentBlock], invocation_state: dict[str, Any] | None = None, **kwargs: Any
) -> GraphResult:
"""Invoke the graph synchronously.
Args:
task: The task to execute
invocation_state: Additional state/context passed to underlying agents.
Defaults to None to avoid mutable default argument issues.
**kwargs: Keyword arguments allowing backward compatible future changes.
"""
if invocation_state is None:
invocation_state = {}
def execute() -> GraphResult:
return asyncio.run(self.invoke_async(task, invocation_state, **kwargs))
with ThreadPoolExecutor() as executor:
future = executor.submit(execute)
return future.result()
async def invoke_async(
self, task: str | list[ContentBlock], invocation_state: dict[str, Any] | None = None, **kwargs: Any
) -> GraphResult:
"""Invoke the graph asynchronously.
Args:
task: The task to execute
invocation_state: Additional state/context passed to underlying agents.
Defaults to None to avoid mutable default argument issues - a new empty dict
is created if None is provided.
**kwargs: Keyword arguments allowing backward compatible future changes.
"""
if invocation_state is None:
invocation_state = {}
logger.debug("task=<%s> | starting graph execution", task)
# Initialize state
start_time = time.time()
self.state = GraphState(
status=Status.EXECUTING,
task=task,
total_nodes=len(self.nodes),
edges=[(edge.from_node, edge.to_node) for edge in self.edges],
entry_points=list(self.entry_points),
start_time=start_time,
)
span = self.tracer.start_multiagent_span(task, "graph")
with trace_api.use_span(span, end_on_exit=True):
try:
logger.debug(
"max_node_executions=<%s>, execution_timeout=<%s>s, node_timeout=<%s>s | graph execution config",
self.max_node_executions or "None",
self.execution_timeout or "None",
self.node_timeout or "None",
)
await self._execute_graph(invocation_state)
# Set final status based on execution results
if self.state.failed_nodes:
self.state.status = Status.FAILED
elif self.state.status == Status.EXECUTING: # Only set to COMPLETED if still executing and no failures
self.state.status = Status.COMPLETED
logger.debug("status=<%s> | graph execution completed", self.state.status)
except Exception:
logger.exception("graph execution failed")
self.state.status = Status.FAILED
raise
finally:
self.state.execution_time = round((time.time() - start_time) * 1000)
return self._build_result()
def _validate_graph(self, nodes: dict[str, GraphNode]) -> None:
"""Validate graph nodes for duplicate instances."""
# Check for duplicate node instances
seen_instances = set()
for node in nodes.values():
if id(node.executor) in seen_instances:
raise ValueError("Duplicate node instance detected. Each node must have a unique object instance.")
seen_instances.add(id(node.executor))
# Validate Agent-specific constraints for each node
_validate_node_executor(node.executor)
async def _execute_graph(self, invocation_state: dict[str, Any]) -> None:
"""Unified execution flow with conditional routing."""
ready_nodes = list(self.entry_points)
while ready_nodes:
# Check execution limits before continuing
should_continue, reason = self.state.should_continue(
max_node_executions=self.max_node_executions,
execution_timeout=self.execution_timeout,
)
if not should_continue:
self.state.status = Status.FAILED
logger.debug("reason=<%s> | stopping execution", reason)
return # Let the top-level exception handler deal with it
current_batch = ready_nodes.copy()
ready_nodes.clear()
# Execute current batch of ready nodes concurrently
tasks = [asyncio.create_task(self._execute_node(node, invocation_state)) for node in current_batch]
for task in tasks:
await task
# Find newly ready nodes after batch execution
# We add all nodes in current batch as completed batch,
# because a failure would throw exception and code would not make it here
ready_nodes.extend(self._find_newly_ready_nodes(current_batch))
def _find_newly_ready_nodes(self, completed_batch: list["GraphNode"]) -> list["GraphNode"]:
"""Find nodes that became ready after the last execution."""
newly_ready = []
for _node_id, node in self.nodes.items():
if self._is_node_ready_with_conditions(node, completed_batch):
newly_ready.append(node)
return newly_ready
def _is_node_ready_with_conditions(self, node: GraphNode, completed_batch: list["GraphNode"]) -> bool:
"""Check if a node is ready considering conditional edges."""
# Get incoming edges to this node
incoming_edges = [edge for edge in self.edges if edge.to_node == node]
# Check if at least one incoming edge condition is satisfied
for edge in incoming_edges:
if edge.from_node in completed_batch:
if edge.should_traverse(self.state):
logger.debug(
"from=<%s>, to=<%s> | edge ready via satisfied condition", edge.from_node.node_id, node.node_id
)
return True
else:
logger.debug(
"from=<%s>, to=<%s> | edge condition not satisfied", edge.from_node.node_id, node.node_id
)
return False
async def _execute_node(self, node: GraphNode, invocation_state: dict[str, Any]) -> None:
"""Execute a single node with error handling and timeout protection."""
# Reset the node's state if reset_on_revisit is enabled and it's being revisited
if self.reset_on_revisit and node in self.state.completed_nodes:
logger.debug("node_id=<%s> | resetting node state for revisit", node.node_id)
node.reset_executor_state()
# Remove from completed nodes since we're re-executing it
self.state.completed_nodes.remove(node)
node.execution_status = Status.EXECUTING
logger.debug("node_id=<%s> | executing node", node.node_id)
start_time = time.time()
try:
# Build node input from satisfied dependencies
node_input = self._build_node_input(node)
# Execute with timeout protection (only if node_timeout is set)
try:
# Execute based on node type and create unified NodeResult
if isinstance(node.executor, MultiAgentBase):
if self.node_timeout is not None:
multi_agent_result = await asyncio.wait_for(
node.executor.invoke_async(node_input, invocation_state),
timeout=self.node_timeout,
)
else:
multi_agent_result = await node.executor.invoke_async(node_input, invocation_state)
# Create NodeResult with MultiAgentResult directly
node_result = NodeResult(
result=multi_agent_result, # type is MultiAgentResult
execution_time=multi_agent_result.execution_time,
status=Status.COMPLETED,
accumulated_usage=multi_agent_result.accumulated_usage,
accumulated_metrics=multi_agent_result.accumulated_metrics,
execution_count=multi_agent_result.execution_count,
)
elif isinstance(node.executor, Agent):
if self.node_timeout is not None:
agent_response = await asyncio.wait_for(
node.executor.invoke_async(node_input, **invocation_state),
timeout=self.node_timeout,
)
else:
agent_response = await node.executor.invoke_async(node_input, **invocation_state)
# Extract metrics from agent response
usage = Usage(inputTokens=0, outputTokens=0, totalTokens=0)
metrics = Metrics(latencyMs=0)
if hasattr(agent_response, "metrics") and agent_response.metrics:
if hasattr(agent_response.metrics, "accumulated_usage"):
usage = agent_response.metrics.accumulated_usage
if hasattr(agent_response.metrics, "accumulated_metrics"):
metrics = agent_response.metrics.accumulated_metrics
node_result = NodeResult(
result=agent_response, # type is AgentResult
execution_time=round((time.time() - start_time) * 1000),
status=Status.COMPLETED,
accumulated_usage=usage,
accumulated_metrics=metrics,
execution_count=1,
)
else:
raise ValueError(f"Node '{node.node_id}' of type '{type(node.executor)}' is not supported")
except asyncio.TimeoutError:
timeout_msg = f"Node '{node.node_id}' execution timed out after {self.node_timeout}s"
logger.exception(
"node=<%s>, timeout=<%s>s | node execution timed out after timeout",
node.node_id,
self.node_timeout,
)
raise Exception(timeout_msg) from None
# Mark as completed
node.execution_status = Status.COMPLETED
node.result = node_result
node.execution_time = node_result.execution_time
self.state.completed_nodes.add(node)
self.state.results[node.node_id] = node_result
self.state.execution_order.append(node)
# Accumulate metrics
self._accumulate_metrics(node_result)
logger.debug(
"node_id=<%s>, execution_time=<%dms> | node completed successfully", node.node_id, node.execution_time
)
except Exception as e:
logger.error("node_id=<%s>, error=<%s> | node failed", node.node_id, e)
execution_time = round((time.time() - start_time) * 1000)
# Create a NodeResult for the failed node
node_result = NodeResult(
result=e, # Store exception as result
execution_time=execution_time,
status=Status.FAILED,
accumulated_usage=Usage(inputTokens=0, outputTokens=0, totalTokens=0),
accumulated_metrics=Metrics(latencyMs=execution_time),
execution_count=1,
)
node.execution_status = Status.FAILED
node.result = node_result
node.execution_time = execution_time
self.state.failed_nodes.add(node)
self.state.results[node.node_id] = node_result # Store in results for consistency
raise
def _accumulate_metrics(self, node_result: NodeResult) -> None:
"""Accumulate metrics from a node result."""
self.state.accumulated_usage["inputTokens"] += node_result.accumulated_usage.get("inputTokens", 0)
self.state.accumulated_usage["outputTokens"] += node_result.accumulated_usage.get("outputTokens", 0)
self.state.accumulated_usage["totalTokens"] += node_result.accumulated_usage.get("totalTokens", 0)
self.state.accumulated_metrics["latencyMs"] += node_result.accumulated_metrics.get("latencyMs", 0)
self.state.execution_count += node_result.execution_count
def _build_node_input(self, node: GraphNode) -> list[ContentBlock]:
"""Build input text for a node based on dependency outputs.
Example formatted output:
```
Original Task: Analyze the quarterly sales data and create a summary report
Inputs from previous nodes:
From data_processor:
- Agent: Sales data processed successfully. Found 1,247 transactions totaling $89,432.
- Agent: Key trends: 15% increase in Q3, top product category is Electronics.
From validator:
- Agent: Data validation complete. All records verified, no anomalies detected.
```
"""
# Get satisfied dependencies
dependency_results = {}
for edge in self.edges:
if (
edge.to_node == node
and edge.from_node in self.state.completed_nodes
and edge.from_node.node_id in self.state.results
):
if edge.should_traverse(self.state):
dependency_results[edge.from_node.node_id] = self.state.results[edge.from_node.node_id]
if not dependency_results:
# No dependencies - return task as ContentBlocks
if isinstance(self.state.task, str):
return [ContentBlock(text=self.state.task)]
else:
return self.state.task
# Combine task with dependency outputs
node_input = []
# Add original task
if isinstance(self.state.task, str):
node_input.append(ContentBlock(text=f"Original Task: {self.state.task}"))
else:
# Add task content blocks with a prefix
node_input.append(ContentBlock(text="Original Task:"))
node_input.extend(self.state.task)
# Add dependency outputs
node_input.append(ContentBlock(text="\nInputs from previous nodes:"))
for dep_id, node_result in dependency_results.items():
node_input.append(ContentBlock(text=f"\nFrom {dep_id}:"))
# Get all agent results from this node (flattened if nested)
agent_results = node_result.get_agent_results()
for result in agent_results:
agent_name = getattr(result, "agent_name", "Agent")
result_text = str(result)
node_input.append(ContentBlock(text=f" - {agent_name}: {result_text}"))
return node_input
def _build_result(self) -> GraphResult:
"""Build graph result from current state."""
return GraphResult(
status=self.state.status,
results=self.state.results,
accumulated_usage=self.state.accumulated_usage,
accumulated_metrics=self.state.accumulated_metrics,
execution_count=self.state.execution_count,
execution_time=self.state.execution_time,
total_nodes=self.state.total_nodes,
completed_nodes=len(self.state.completed_nodes),
failed_nodes=len(self.state.failed_nodes),
execution_order=self.state.execution_order,
edges=self.state.edges,
entry_points=self.state.entry_points,
)