Postman转k6脚本后Content-Type未更新致请求报错排查

前提 #

Postman中对应的请求可正常运行。

执行的操作 #

• 运行postman-to-k6转换命令：

  postman-to-k6 loadTest.postman_collection.json -o k6-script.js
  

• 带HTTP调试参数执行k6脚本：

  k6 run --out csv=test_results.csv k6-script.js --http-debug="full"
  

自动生成的k6脚本 #

// Auto-generated by the postman-to-k6 converter
export let options = { maxRedirects: 4 };

const Request = Symbol.for("request");
postman[Symbol.for("initial")]({
  options
});

export default function() {
  postman[Request]({
    name: "Campaigns",
    id: "189fa369-87c7-4dcb-bf9d-e812d4efd6e8",
    method: "POST",
    address: "https://api.beta.detail-page.journeys.a2z.com/graphql",
    data:
      '{"query":"\n        query campaigns($projectId: ID!) {\n            campaigns(projectId: $projectId) {\n                id\n                createdAt\n                createdBy\n                typeId\n                originalPodData\n                useReactAppUrl\n            }\n        }\n        ","variables":{"projectId":"ghost:PublishTest 2:US"}}',
    headers: {
      "Content-Type": "application/json",
      identitytoken: <Backend-JWT-Token>
    },
    auth(config, Var) {
      const address = new URI(config.address);
      const options = {
        method: "POST",
        protocol: address.protocol(),
        hostname: address.hostname(),
        port: address.port(),
        path: address.path() + address.search(),
        body: config.data,
        region: "us-west-2",
        service: <Service-Name>
      };
      const credential = {
        accessKeyId: <accessKey-ID>,
        secretAccessKey: <Secret-key>,
        sessionToken: <Session-token>
      };
      const signed = aws4.sign(options, credential);
      const [path, query = ""] = signed.path.split("?");
      config.address = new URI()
        .protocol(address.protocol())
        .hostname(signed.hostname)
        .path(path)
        .query(query)
        .toString();
      Object.assign(config.headers, signed.headers);
    }
  });
}

请求日志 #

POST /graphql HTTP/1.1
Host: api.beta.detail-page.journeys.a2z.com
User-Agent: k6/0.40.0 (https://k6.io/)
Content-Length: 354
Authorization: AWS4-HMAC-SHA256 Credential=ASIAVGC47R5TZOZXHHNM/20221025/us-west-2/execute-api/aws4_request, SignedHeaders=content-length;content-type;host;x-amz-date;x-amz-security-token, Signature=9dceffc3e3376fd6f9b860025ce9a82454f740bd189ffa8da3c0a6d8d83e230f
Content-Type: application/x-www-form-urlencoded; charset=utf-8
Identitytoken: <Identity-token>
X-Amz-Date: 20221025T200827Z
X-Amz-Security-Token: <Security-token>
Accept-Encoding: gzip

响应日志 #

HTTP/2.0 500 Internal Server Error
Content-Length: 61
Access-Control-Allow-Origin: *
Content-Type: text/html; charset=utf-8
Date: Tue, 25 Oct 2022 20:08:27 GMT
Etag: W/"3d-hTSca7jJI4XwK3C0Li5aF8JIkvc"
X-Amz-Apigw-Id: ak9JUEu-PHcFefQ=
X-Amzn-Remapped-Connection: close
X-Amzn-Remapped-Content-Length: 61
X-Amzn-Remapped-Date: Tue, 25 Oct 2022 20:08:27 GMT
X-Amzn-Requestid: bee58104-704c-4cb0-9ec4-399e6f69450d
X-Amzn-Trace-Id: Root=1-6358423b-5dc39ed81536364944f6bd11
X-Powered-By: Express

错误提示 #

POST body missing. Did you forget use body-parser middleware? group= iter=0 request_id=ad10989c-1023-46c9-5f34-e381a7d5795b scenario=default source=http-debug vu=1

问题分析 #

从请求日志可见，实际发送的Content-Type被篡改成了application/x-www-form-urlencoded，但脚本里明明配置了application/json。根源在AWS签名流程：

1. aws4.sign方法若未收到明确的Content-Type，会默认设置为application/x-www-form-urlencoded
2. 后续Object.assign(config.headers, signed.headers)用签名后的头部覆盖了原配置，导致正确的Content-Type丢失

服务器因Content-Type不匹配，无法解析JSON格式的请求体，因此抛出"POST body missing"错误。

解决方法 #

修改脚本中的auth函数，在签名配置里明确指定Content-Type，并在签名完成后强制保留正确的头部：

auth(config, Var) {
  const address = new URI(config.address);
  const options = {
    method: "POST",
    protocol: address.protocol(),
    hostname: address.hostname(),
    port: address.port(),
    path: address.path() + address.search(),
    body: config.data,
    region: "us-west-2",
    service: <Service-Name>,
    // 新增：将原请求的Content-Type加入签名配置
    headers: {
      "Content-Type": config.headers["Content-Type"]
    }
  };
  const credential = {
    accessKeyId: <accessKey-ID>,
    secretAccessKey: <Secret-key>,
    sessionToken: <Session-token>
  };
  const signed = aws4.sign(options, credential);
  const [path, query = ""] = signed.path.split("?");
  config.address = new URI()
    .protocol(address.protocol())
    .hostname(signed.hostname)
    .path(path)
    .query(query)
    .toString();
  Object.assign(config.headers, signed.headers);
  // 强制覆盖Content-Type，确保最终发送的是application/json
  config.headers["Content-Type"] = "application/json";
}

修改后重新运行k6脚本，请求日志中的Content-Type会变为application/json，服务器就能正确解析请求体，错误将消失。

内容的提问来源于stack exchange，提问作者Dharight