时间旅行¶

LangGraph 提供 时间旅行 功能，可以 从先前的检查点恢复执行——既可以重播相同的状态，也可以修改状态以探索替代方案。在所有情况下，恢复过去的执行都会在历史中产生 一个新的分支。

使用时间旅行¶

要在 LangGraph 中使用时间旅行：

使用 LangGraph SDK 的 client.runs.wait 或 client.runs.stream API，以初始输入 运行图。
识别现有线程中的检查点：使用 client.threads.get_history 方法检索特定 thread_id 的执行历史并定位所需的 checkpoint_id。或者，在您希望执行暂停的节点之前设置一个断点。然后您可以找到在该断点之前记录的最新检查点。
（可选）修改图状态：使用 client.threads.update_state 方法修改检查点处的图状态，并从替代状态恢复执行。
从检查点恢复执行：使用 client.runs.wait 或 client.runs.stream API，并输入 None 以及适当的 thread_id 和 checkpoint_id。

示例¶

示例图

from typing_extensions import TypedDict, NotRequired
from langgraph.graph import StateGraph, START, END
from langchain.chat_models import init_chat_model
from langgraph.checkpoint.memory import InMemorySaver

class State(TypedDict):
    topic: NotRequired[str]
    joke: NotRequired[str]

llm = init_chat_model(
    "anthropic:claude-3-7-sonnet-latest",
    temperature=0,
)

def generate_topic(state: State):
    """LLM call to generate a topic for the joke"""
    msg = llm.invoke("Give me a funny topic for a joke")
    return {"topic": msg.content}

def write_joke(state: State):
    """LLM call to write a joke based on the topic"""
    msg = llm.invoke(f"Write a short joke about {state['topic']}")
    return {"joke": msg.content}

# Build workflow
builder = StateGraph(State)

# Add nodes
builder.add_node("generate_topic", generate_topic)
builder.add_node("write_joke", write_joke)

# Add edges to connect nodes
builder.add_edge(START, "generate_topic")
builder.add_edge("generate_topic", "write_joke")

# Compile
graph = builder.compile()

1. 运行图¶

PythonJavaScriptcURL

from langgraph_sdk import get_client
client = get_client(url=<DEPLOYMENT_URL>)

# Using the graph deployed with the name "agent"
assistant_id = "agent"

# create a thread
thread = await client.threads.create()
thread_id = thread["thread_id"]

# Run the graph
result = await client.runs.wait(
    thread_id,
    assistant_id,
    input={}
)

import { Client } from "@langchain/langgraph-sdk";
const client = new Client({ apiUrl: <DEPLOYMENT_URL> });

// Using the graph deployed with the name "agent"
const assistantID = "agent";

// create a thread
const thread = await client.threads.create();
const threadID = thread["thread_id"];

// Run the graph
const result = await client.runs.wait(
  threadID,
  assistantID,
  { input: {}}
);

创建线程

curl --request POST \
--url <DEPLOYMENT_URL>/threads \
--header 'Content-Type: application/json' \
--data '{}'

运行图

curl --request POST \
--url <DEPLOYMENT_URL>/threads/<THREAD_ID>/runs/wait \
--header 'Content-Type: application/json' \
--data "{
  \"assistant_id\": \"agent\",
  \"input\": {}
}"

2. 识别检查点¶

PythonJavaScriptcURL

# The states are returned in reverse chronological order.
states = await client.threads.get_history(thread_id)
selected_state = states[1]
print(selected_state)

// The states are returned in reverse chronological order.
const states = await client.threads.getHistory(threadID);
const selectedState = states[1];
console.log(selectedState);

curl --request GET \
--url <DEPLOYMENT_URL>/threads/<THREAD_ID>/history \
--header 'Content-Type: application/json'

3. 更新状态（可选）¶

update_state 将创建一个新的检查点。新的检查点将与同一线程关联，但具有新的检查点 ID。

PythonJavaScriptcURL

new_config = await client.threads.update_state(
    thread_id,
    {"topic": "chickens"},
    checkpoint_id=selected_state["checkpoint_id"]
)
print(new_config)

const newConfig = await client.threads.updateState(
  threadID,
  {
    values: { "topic": "chickens" },
    checkpointId: selectedState["checkpoint_id"]
  }
);
console.log(newConfig);

curl --request POST \
--url <DEPLOYMENT_URL>/threads/<THREAD_ID>/state \
--header 'Content-Type: application/json' \
--data "{
  \"assistant_id\": \"agent\",
  \"checkpoint_id\": <CHECKPOINT_ID>,
  \"values\": {\"topic\": \"chickens\"}
}"

4. 从检查点恢复执行¶

PythonJavaScriptcURL

await client.runs.wait(
    thread_id,
    assistant_id,
    input=None,
    checkpoint_id=new_config["checkpoint_id"]
)

await client.runs.wait(
  threadID,
  assistantID,
  {
    input: null,
    checkpointId: newConfig["checkpoint_id"]
  }
);

curl --request POST \
--url <DEPLOYMENT_URL>/threads/<THREAD_ID>/runs/wait \
--header 'Content-Type: application/json' \
--data "{
  \"assistant_id\": \"agent\",
  \"checkpoint_id\": <CHECKPOINT_ID>
}"

了解更多¶

LangGraph 时间旅行指南：了解更多关于在 LangGraph 中使用时间旅行的信息。