javascript - 同步链接 Promise

Question

我正在使用 AWS Lambda。我正在尝试解密异步函数中的 key ，然后向另一个 URL 发出 POST 请求，这取决于首先从第一次调用中获取 key 。

module.exports = function (payload) {
    return new Promise(function(resolve, reject) {
        var headers = config.Headers;
        decrypt(headers.Authorization)
            .then(function (auth_token) {
                headers.Authorization = 'Basic ' + auth_token;
                console.log('dispatch got the key from kms');
                return makePostCall(headers, payload);
            })
             .then(function (changeNumber){
                 console.log(changeNumber);
                 return resolve(changeNumber);
            })
            .catch (function (error) {
                console.error('Error during dispatch: ' + error);
                return reject(error);
            });
    });
};

decrypt 和 makePostCall 调用均返回 reject 或 resolve。在本地运行良好，但在 Lambda 上运行时，仅成功运行几次，这让我相信问题出在 makePostCall 函数的异步调用上。我得到的错误(来自 catch)是:

Error during dispatch: null

我需要先运行解密->获取 key ->然后MakePostCall。

编辑: makePostCall 如下所示:

function makePostCall(headers, payload) {
    return new Promise(function (resolve, reject) {
        const url = config.serviceNowEndpoint + config.serviceNowChangeUri;
        request.post({
            url: url,
            method: 'POST',
            headers: headers,
            json: payload
        }, function (error, response, body) {
            if (!error) {
                return resolve(body.change_request.number);
            }
            else {
                return reject(new Error('Returned with status code: ' + response.statusCode));
            }
        });
    });
}

更多编辑:根据@Jaromanda X的建议，将代码修改为:

module.exports = function (payload) {
    var headers = config.Headers;
    return decrypt(headers.Authorization)
        .then(function (auth_token) {
            headers.Authorization = 'Basic ' + auth_token;
            console.log('dispatch got the key from kms');
            return makePostCall(headers, payload);
        })
        .catch (function (error) {
            console.error('Error during dispatch: ' + error);
            return error;
        });
};

问题仍然存在。在本地运行良好，但在 Lambda 上异步

编辑添加解密代码:

const AWS = require('aws-sdk');
const config = require('../config/config');

module.exports = function(token)  {
    return new Promise(function (resolve, reject) {
        const kms = new AWS.KMS({ region: config.aws_region.region});

        const params = {
            CiphertextBlob: new Buffer(token, 'base64')
        };
        kms.decrypt(params, function (err, data) {
            if (!err) {
                console.log('decrypted successfully');
                return resolve(data.Plaintext.toString());
            } else {
                return reject(`${err.message}`);
            }
        });
    });
};

Answer 1

这是一个 AWS lambda 错误。请参阅issue at Bluebird's repo和 basic reproducing code对于这个问题。

这个问题实际上与 bluebird 无关，而是与 lambda 部署上的异步代码处理和调度有关。 https://github.com/nervous-systems/cljs-lambda/issues/62 。这是重现该错误的另一个问题:https://github.com/nervous-systems/cljs-lambda/issues/62 。

用户提出了一个常见问题:

Oh my god. Just in case anyone else lands here and makes my mistake: make sure you haven't accidentally deployed AWS.config.update(...) using a localhost endpoint instead of an actual AWS region-specific endpoint. That can present with similar symptoms as above (say, if the only async function you're using is accessing a DynamoDB document client) but for utterly different reasons.