How to add node retry policies

There are many use cases where you may wish for your node to have a custom retry policy. Some examples of when you may wish to do this is 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 retryPolicy parameter to the addNode function. The retryPolicy parameter takes in a RetryPolicy named tuple object. Below we instantiate a RetryPolicy object with the default parameters:

import { RetryPolicy } from "@langchain/langgraph"

const retryPolicy: RetryPolicy = {};

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 addNode function. In the example below we pass two different retry policies to each of our nodes:

import Database from "better-sqlite3"
import { ChatAnthropic } from "@langchain/anthropic"
import { MessagesAnnotation, StateGraph, START, END } from "@langchain/langgraph"
import { AIMessage } from "@langchain/core/messages"

// Create an in-memory database
const db: typeof Database.prototype = new Database(':memory:');

const model = new ChatAnthropic({ model: "claude-3-5-sonnet-20240620" });

const callModel = async (state: typeof MessagesAnnotation.State) => {
    const response = await model.invoke(state.messages);
    return { messages: [response] };
}

const queryDatabase = async (state: typeof MessagesAnnotation.State) => {
    const queryResult: string = JSON.stringify(db.prepare("SELECT * FROM Artist LIMIT 10;").all());

    return { messages: [new AIMessage({content: "queryResult"})]};
};

const workflow = new StateGraph(MessagesAnnotation)
    // Define the two nodes we will cycle between
    .addNode("call_model", callModel, { retryPolicy: {maxAttempts: 5}})
    .addNode("query_database", queryDatabase, { retryPolicy: { retryOn: (e: any): boolean => {
        if (e instanceof Database.SqliteError) {
          // Retry on "SQLITE_BUSY" error
          return e.code === 'SQLITE_BUSY';
        }
        return false; // Don't retry on other errors
      }}})
    .addEdge(START, "call_model")
    .addEdge("call_model", "query_database")
    .addEdge("query_database", END);

const graph = workflow.compile();