Netlify Background Function POST请求CORS问题排查求助

我创建了一个Netlify Background Function处理POST请求，需求是接收请求、执行generateEmbeddings函数并返回响应。切换到Background Function前用Serverless Function时没有CORS问题，但因为大请求耗时超10秒，不得不改用Background Function，现在发起POST请求时遇到跨源被阻止的错误，即使在函数里设置了CORS头也无效。

报错信息 #

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://my-netlify-site.netlify.app/.netlify/functions/webhooks-background. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 202.
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://my-netlify-site.netlify.app/.netlify/functions/webhooks-background. (Reason: CORS request did not succeed). Status code: (null).

初始Background Function代码 #

exports.handler = async (event) => {
  const headers = {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "POST, OPTIONS",
    "Access-Control-Allow-Headers": "Content-Type",
    "Content-Type": "application/json",  
  };
  if (event.httpMethod === "OPTIONS") {
    return {
      statusCode: 204,  
      headers,
      body: '', 
    };
  } else if (event.httpMethod === "POST") {
    try {
      const parsedData = JSON.parse(event.body);
      await generateEmbeddings(parsedData);
      return {
        statusCode: 202,
        headers: headers,
        body: "Webhook data received",
      };
    } catch (error) {
      console.error("Error handling request:", error);
      return {
        statusCode: 500,
        headers: headers,
        body: "Internal Server Error",
      };
    }
  } else {
    return {
      statusCode: 405,  
      headers,
      body: JSON.stringify({ message: "HTTP Method not supported. Use OPTIONS or POST." }),
    };
  }
};

后续更新 #

我已经让Background Function在本地正常运行，但生产环境仍存在CORS问题，核心是请求头配置：本地开发时头设置正确，但生产环境无效，已通过curl验证这一点。

最初在netlify.toml文件中设置头，生产环境未生效，之后改用_headers文件，该文件放置在项目根目录。

更新后的Background Function代码 #

const { generateEmbeddings } = require("../../scripts/embedding");

exports.handler = async (event) => {
  if (event.httpMethod === "OPTIONS") {
    console.log("OPTIONS request received");
    return; 
  } 
  if (event.httpMethod === "POST") {
    try {
      const parsedData = JSON.parse(event.body);
      await generateEmbeddings(parsedData);
      console.log("Webhook data processed in the background");
    } catch (error) {
      console.error("Error handling request:", error);
    }
  }
};

_headers文件内容 #

/*
  Cache-Control: no-cache
  Access-Control-Allow-Origin: *

/.netlify/functions/*
  Access-Control-Allow-Origin: *
  Access-Control-Allow-Headers: Content-Type, Authorization
  Access-Control-Allow-Methods: GET, POST, OPTIONS

内容的提问来源于stack exchange，提问作者Matt