How to use Async and Await with AWS SDK Javascript

问题:

I am working with the AWS SDK using the KMS libary. I would like to use async and await instead of callbacks.

import AWS, { KMS } from "aws-sdk";

this.kms = new AWS.KMS();

const key = await this.kms.generateDataKey();

However this does not work, when wrapped in an async function.

How can i use async and await here?

回答1:

If you are using aws-sdk with version > 2.x, you can tranform a aws.Request to a promise with chain .promise() function. For your case:

  try {
    let key = await kms.generateDataKey().promise();
  } catch (e) {
    console.log(e);
  }

the key is a KMS.Types.GenerateDataKeyResponse - the first param of callback(in callback style).

The e is a AWSError - The second param of callback func

note: await expression only allowed within an async function

回答2:

await requires a Promise. generateDataKey() returns a AWS.Request, not a Promise. AWS.Request are EventEmitters (more or less) but have a promise method that you can use.

import AWS, {
  KMS
} from "aws-sdk";

(async function() {
  const kms = new AWS.KMS();
  const keyReq = kms.generateDataKey()
  const key = await keyReq.promise();

  // Or just:
  // const key = await kms.generateDataKey().promise()
}());