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*   [LangChain Expression Language](/v0.1/docs/expression_language/)
*   How to
*   Cancelling requests

Cancelling requests
===================

You can cancel a LCEL request by binding a `signal`.

tip

See [this section for general instructions on installing integration packages](/v0.1/docs/get_started/installation/#installing-integration-packages).

*   npm
*   Yarn
*   pnpm

    npm install @langchain/openai

    yarn add @langchain/openai

    pnpm add @langchain/openai

    import { ChatOpenAI } from "@langchain/openai";import { PromptTemplate } from "@langchain/core/prompts";const controller = new AbortController();// Create a new LLMChain from a PromptTemplate and an LLM in streaming mode.const llm = new ChatOpenAI({ temperature: 0.9 });const model = llm.bind({ signal: controller.signal });const prompt = PromptTemplate.fromTemplate(  "Please write a 500 word essay about {topic}.");const chain = prompt.pipe(model);// Call `controller.abort()` somewhere to cancel the request.setTimeout(() => {  controller.abort();}, 3000);try {  // Call the chain with the inputs and a callback for the streamed tokens  const stream = await chain.stream({ topic: "Bonobos" });  for await (const chunk of stream) {    console.log(chunk);  }} catch (e) {  console.log(e);  // Error: Cancel: canceled}

#### API Reference:

*   [ChatOpenAI](https://api.js.langchain.com/classes/langchain_openai.ChatOpenAI.html) from `@langchain/openai`
*   [PromptTemplate](https://api.js.langchain.com/classes/langchain_core_prompts.PromptTemplate.html) from `@langchain/core/prompts`

Note, this will only cancel the outgoing request if the underlying provider exposes that option. LangChain will cancel the underlying request if possible, otherwise it will cancel the processing of the response.

* * *

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