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如何分派自定义回调事件

先决条件

本指南假设你熟悉以下概念

在某些情况下,您可能希望从 Runnable 中分派自定义回调事件,以便可以在自定义回调处理程序中或通过 Astream 事件 API 显示该事件。

例如,如果您的工具有多个步骤且运行时间较长,则可以在步骤之间分派自定义事件,并使用这些自定义事件来监视进度。您还可以将这些自定义事件展示给应用程序的最终用户,以向他们显示当前任务的进展情况。

要分派自定义事件,您需要为事件确定两个属性:namedata

属性类型描述
namestr事件的用户定义名称。
dataAny与事件关联的数据。这可以是任何内容,但我们建议将其设为 JSON 可序列化。
重要提示
  • 分派自定义回调事件需要 langchain-core>=0.2.15
  • 自定义回调事件只能从现有的 Runnable 中分派。
  • 如果使用 astream_events,则必须使用 version='v2' 才能看到自定义事件。
  • LangSmith 尚不支持发送或渲染自定义回调事件。
兼容性

如果您在 python<=3.10 中运行异步代码,LangChain 无法自动将配置(包括 astream_events() 所需的回调)传播到子 runnable。这是您可能无法看到从自定义 runnable 或工具发出事件的常见原因。

如果您正在运行 python<=3.10,则需要在异步环境中手动将 RunnableConfig 对象传播到子 runnable。有关如何手动传播配置的示例,请参阅下面 bar RunnableLambda 的实现。

如果您正在运行 python>=3.11,则 RunnableConfig 将自动传播到异步环境中的子 runnable。但是,如果您的代码可能在其他 Python 版本中运行,手动传播 RunnableConfig 仍然是一个好主意。

Astream 事件 API

使用自定义事件的最有效方法是通过 Astream 事件 API

我们可以使用 async adispatch_custom_event API 在异步设置中发出自定义事件。

重要提示

要通过 astream 事件 API 查看自定义事件,您需要使用较新的 v2 API 的 astream_events

from langchain_core.callbacks.manager import (
adispatch_custom_event,
)
from langchain_core.runnables import RunnableLambda
from langchain_core.runnables.config import RunnableConfig


@RunnableLambda
async def foo(x: str) -> str:
await adispatch_custom_event("event1", {"x": x})
await adispatch_custom_event("event2", 5)
return x


async for event in foo.astream_events("hello world", version="v2"):
print(event)
{'event': 'on_chain_start', 'data': {'input': 'hello world'}, 'name': 'foo', 'tags': [], 'run_id': 'f354ffe8-4c22-4881-890a-c1cad038a9a6', 'metadata': {}, 'parent_ids': []}
{'event': 'on_custom_event', 'run_id': 'f354ffe8-4c22-4881-890a-c1cad038a9a6', 'name': 'event1', 'tags': [], 'metadata': {}, 'data': {'x': 'hello world'}, 'parent_ids': []}
{'event': 'on_custom_event', 'run_id': 'f354ffe8-4c22-4881-890a-c1cad038a9a6', 'name': 'event2', 'tags': [], 'metadata': {}, 'data': 5, 'parent_ids': []}
{'event': 'on_chain_stream', 'run_id': 'f354ffe8-4c22-4881-890a-c1cad038a9a6', 'name': 'foo', 'tags': [], 'metadata': {}, 'data': {'chunk': 'hello world'}, 'parent_ids': []}
{'event': 'on_chain_end', 'data': {'output': 'hello world'}, 'run_id': 'f354ffe8-4c22-4881-890a-c1cad038a9a6', 'name': 'foo', 'tags': [], 'metadata': {}, 'parent_ids': []}

在 python <= 3.10 中,您必须手动传播配置!

from langchain_core.callbacks.manager import (
adispatch_custom_event,
)
from langchain_core.runnables import RunnableLambda
from langchain_core.runnables.config import RunnableConfig


@RunnableLambda
async def bar(x: str, config: RunnableConfig) -> str:
"""An example that shows how to manually propagate config.

You must do this if you're running python<=3.10.
"""
await adispatch_custom_event("event1", {"x": x}, config=config)
await adispatch_custom_event("event2", 5, config=config)
return x


async for event in bar.astream_events("hello world", version="v2"):
print(event)
{'event': 'on_chain_start', 'data': {'input': 'hello world'}, 'name': 'bar', 'tags': [], 'run_id': 'c787b09d-698a-41b9-8290-92aaa656f3e7', 'metadata': {}, 'parent_ids': []}
{'event': 'on_custom_event', 'run_id': 'c787b09d-698a-41b9-8290-92aaa656f3e7', 'name': 'event1', 'tags': [], 'metadata': {}, 'data': {'x': 'hello world'}, 'parent_ids': []}
{'event': 'on_custom_event', 'run_id': 'c787b09d-698a-41b9-8290-92aaa656f3e7', 'name': 'event2', 'tags': [], 'metadata': {}, 'data': 5, 'parent_ids': []}
{'event': 'on_chain_stream', 'run_id': 'c787b09d-698a-41b9-8290-92aaa656f3e7', 'name': 'bar', 'tags': [], 'metadata': {}, 'data': {'chunk': 'hello world'}, 'parent_ids': []}
{'event': 'on_chain_end', 'data': {'output': 'hello world'}, 'run_id': 'c787b09d-698a-41b9-8290-92aaa656f3e7', 'name': 'bar', 'tags': [], 'metadata': {}, 'parent_ids': []}

异步回调处理程序

您还可以通过异步回调处理程序使用分派的事件。

from typing import Any, Dict, List, Optional
from uuid import UUID

from langchain_core.callbacks import AsyncCallbackHandler
from langchain_core.callbacks.manager import (
adispatch_custom_event,
)
from langchain_core.runnables import RunnableLambda
from langchain_core.runnables.config import RunnableConfig


class AsyncCustomCallbackHandler(AsyncCallbackHandler):
async def on_custom_event(
self,
name: str,
data: Any,
*,
run_id: UUID,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
**kwargs: Any,
) -> None:
print(
f"Received event {name} with data: {data}, with tags: {tags}, with metadata: {metadata} and run_id: {run_id}"
)


@RunnableLambda
async def bar(x: str, config: RunnableConfig) -> str:
"""An example that shows how to manually propagate config.

You must do this if you're running python<=3.10.
"""
await adispatch_custom_event("event1", {"x": x}, config=config)
await adispatch_custom_event("event2", 5, config=config)
return x


async_handler = AsyncCustomCallbackHandler()
await foo.ainvoke(1, {"callbacks": [async_handler], "tags": ["foo", "bar"]})
Received event event1 with data: {'x': 1}, with tags: ['foo', 'bar'], with metadata: {} and run_id: a62b84be-7afd-4829-9947-7165df1f37d9
Received event event2 with data: 5, with tags: ['foo', 'bar'], with metadata: {} and run_id: a62b84be-7afd-4829-9947-7165df1f37d9
1

同步回调处理程序

让我们看看如何在同步环境中使用 dispatch_custom_event 发出自定义事件。

必须从现有的 Runnable 中调用 dispatch_custom_event

from typing import Any, Dict, List, Optional
from uuid import UUID

from langchain_core.callbacks import BaseCallbackHandler
from langchain_core.callbacks.manager import (
dispatch_custom_event,
)
from langchain_core.runnables import RunnableLambda
from langchain_core.runnables.config import RunnableConfig


class CustomHandler(BaseCallbackHandler):
def on_custom_event(
self,
name: str,
data: Any,
*,
run_id: UUID,
tags: Optional[List[str]] = None,
metadata: Optional[Dict[str, Any]] = None,
**kwargs: Any,
) -> None:
print(
f"Received event {name} with data: {data}, with tags: {tags}, with metadata: {metadata} and run_id: {run_id}"
)


@RunnableLambda
def foo(x: int, config: RunnableConfig) -> int:
dispatch_custom_event("event1", {"x": x})
dispatch_custom_event("event2", {"x": x})
return x


handler = CustomHandler()
foo.invoke(1, {"callbacks": [handler], "tags": ["foo", "bar"]})
Received event event1 with data: {'x': 1}, with tags: ['foo', 'bar'], with metadata: {} and run_id: 27b5ce33-dc26-4b34-92dd-08a89cb22268
Received event event2 with data: {'x': 1}, with tags: ['foo', 'bar'], with metadata: {} and run_id: 27b5ce33-dc26-4b34-92dd-08a89cb22268
1

后续步骤

您已经了解了如何发出自定义事件,您可以查看有关 astream 事件 的更深入指南,这是利用自定义事件的最简单方法。


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