Javascript 嵌套异步等待函数未在 AWS Lambda 函数中执行

你的代码有几个问题:

1. 嵌套异步函数——您正在创建它，但从未执行它

async () => { // creates an async anonymous arrow function, that's it

}

两种解决方案:

// wrapping the function in an IIFE create and executes it
(async () => {

})();

// give it a name and execute it later
async main() => {

}

main();

2. 通过将传递给forEach的回调声明为async，可以摆脱嵌套的async函数:

data.Items.forEach(async (item, index, array) => { // <--- this is async
  // ...

  const req = new AWS.HttpRequest(appsyncUrl, region);
  const item = {
    input: {
      id: event.sensorId,
      sensorId: event.sensorId,
    },
  };

  // ...
});

3. 末尾的try/catch块不会捕获任何错误.相反，将创建的promise 封装在try/catch块中，并在发生错误事件时从内部拒绝:

try {
  const data = await new Promise((resolve, reject) => {
    const httpRequest = https.request(
      { ...req, host: endpoint },
      (result) => {
        // ...

        result.on("error", (error) => {
          reject(error);
        });

        // ...
      }
    );

    // ...
  });

  return {
    statusCode: 200,
    body: data,
  };
} catch (err) {
  console.log("error", err);
}

4. 在forEach中运行异步操作并不能达到您的目的.您可能打算响应after所有传感器SID都已创建.真正发生的事情是，当第一个sensorId被创建时，你会立即做出响应.这是因为forEach同时触发data.Items次回调.解决这个问题的一个方法是使用map，并返回一系列promise ，然后您可以带着promise 等待.全部的

下面是最终的代码，以及我将如何解决它.作为一个额外的例子，我promise 了ddb.scan个，所以你不会把回调和promise 以及异步/等待混为一谈:

const scanAsync = util.promisify(ddb.scan);

exports.handler = async (event) => {
  const sensorId = event.sensorId;

  try {
    const data = await scanAsync(params);

    const responses = await Promise.all(
      data.Items.map((item) => {
        if (item.sensorId.S == sensorId) {
          console.log("New sensorId was not created. Already Exists.");
          return;
        }

        const req = new AWS.HttpRequest(appsyncUrl, region);
        const item = {
          input: {
            id: event.sensorId,
            sensorId: event.sensorId,
          },
        };

        req.method = "POST";
        req.path = "/graphql";
        req.headers.host = endpoint;
        req.headers["Content-Type"] = "application/json";
        req.body = JSON.stringify({
          query: print(createSensor),
          operationName: "createSensor",
          variables: item,
        });

        if (apiKey) {
          req.headers["x-api-key"] = apiKey;
        } else {
          const signer = new AWS.Signers.V4(req, "appsync", true);
          signer.addAuthorization(
            AWS.config.credentials,
            AWS.util.date.getDate()
          );
        }

        return new Promise((resolve, reject) => {
          const httpRequest = https.request(
            { ...req, host: endpoint },
            (result) => {
              let data = "";

              result.on("data", (chunk) => {
                data += chunk;
              });

              result.on("error", (error) => {
                reject(error);
              });

              result.on("end", () => {
                resolve(JSON.parse(data.toString()));
              });
            }
          );

          httpRequest.write(req.body);
          httpRequest.end();
        });
      })
    );

    return {
      statusCode: 200,
      body: responses,
    };
  } catch (error) {
    console.log("error", error);
  }
};

我希望你能从我的回答中学到一两件事:).如果你有任何问题，请告诉我.