langgraph/examples/node-retries.ipynb

How to add node retry policies

There are many use cases where you may wish for your node to have a custom retry policy, for example if you are calling an API, querying a database, or calling an LLM, etc.

In order to configure the retry policy, you have to pass the retry parameter to the add_node function. The retry parameter takes in a RetryPolicy named tuple object. Below we instantiate a RetryPolicy object with the default parameters:

In [15]:

from langgraph.pregel import RetryPolicy

RetryPolicy()

Out [15]:

RetryPolicy(initial_interval=0.5, backoff_factor=2.0, max_interval=128.0, max_attempts=3, jitter=True, retry_on=<function default_retry_on at 0x1157419e0>)

If you want more information on what each of the parameters does, be sure to read the reference.

Passing a retry policy to a node

Lastly, we can pass RetryPolicy objects when we call the add_node function. In the example below we pass two different retry policies to each of our nodes:

In [21]:

import operator
import sqlite3
from typing import Annotated, Sequence, TypedDict

from langchain_anthropic import ChatAnthropic
from langchain_core.messages import BaseMessage

from langgraph.graph import END, StateGraph, START
from langchain_community.utilities import SQLDatabase
from langchain_core.messages import AIMessage

db = SQLDatabase.from_uri("sqlite:///:memory:")

model = ChatAnthropic(model_name="claude-2.1")


class AgentState(TypedDict):
    messages: Annotated[Sequence[BaseMessage], operator.add]


def query_database(state):
    query_result = db.run("SELECT * FROM Artist LIMIT 10;")
    return {"messages": [AIMessage(content=query_result)]}


def call_model(state):
    response = model.invoke(state["messages"])
    return {"messages": [response]}


# Define a new graph
workflow = StateGraph(AgentState)
workflow.add_node(
    "query_database",
    query_database,
    retry=RetryPolicy(retry_on=sqlite3.OperationalError),
)
workflow.add_node("model", call_model, retry=RetryPolicy(max_attempts=5))
workflow.add_edge(START, "model")
workflow.add_edge("model", "query_database")
workflow.add_edge("query_database", END)

app = workflow.compile()