承诺或asynchronous与节点js
我有大量的代码从S3存储桶中获取图像，将其保存到Lambda上的临时文件中，将其大小调整为4种不同的大小，并根据大小将其保存到不同的文件夹中，然后将图像存回s3存储桶也进入不同的文件夹。
但是，在Lambda上运行时，必须在整个过程结束时调用context.done() ，否则上下文将保持活动状态，直到Lambda超时。
所以我需要在最后一次upload返回时调用context.done() 。
看看这两个选项， async和promises ，这可能需要更less的重构我的代码工作？
// dependencies var AWS = require('aws-sdk'); var gm = require('gm').subClass({ imageMagick: true }); var fs = require("fs"); // get reference to S3 client var s3 = new AWS.S3(); var _800px = { width: 800, destinationPath: "large" }; var _500px = { width: 500, destinationPath: "medium" }; var _200px = { width: 200, destinationPath: "small" }; var _45px = { width: 45, destinationPath: "thumbnail" }; var _sizesArray = [_800px, _500px, _200px, _45px]; var len = _sizesArray.length; module to be exported when in production ports.AwsHandler = function(event, context) { // Read options from the event. var srcBucket = event.Records[0].s3.bucket.name; var srcKey = event.Records[0].s3.object.key; var dstnFolder = "/tmp"; // function to determine paths function _filePath (directory, i) { if ( directory === false ) { return "dst/" + _sizesArray[i].destinationPath + "/" + srcKey; } else if ( directory === true ) { return dstnFolder + "/" + _sizesArray[i].destinationPath + "/" + srcKey; } }; for ( var i = 0; i<len; i++) { fs.mkdir("/tmp" + "/" + _sizesArray[i].destinationPath, function (err) { if (err) { console.log(err); } }); }; // Infer the image type. var typeMatch = srcKey.match(/\.([^.]*)$/); if (!typeMatch) { console.error('unable to infer image type for key ' + srcKey); return; }; var imageType = typeMatch[1]; if (imageType != "jpg" && imageType != "png") { console.log('skipping non-image ' + srcKey); return; }; function download () { s3.getObject({ Bucket: srcBucket, Key: srcKey }, function (err, response) { if (err) { console.error(err); } fs.writeFile("/tmp" + "/" + srcKey, response.Body, function (err) { transform(); }) } ); }; function transform () { var _Key, _Size; for ( var i = 0; i<len; i++ ) { // define path for image write _Key = _filePath (true, i); // define sizes to resize to _Size = _sizesArray[i].width; // resize images gm("/tmp/" + srcKey) .resize(_Size) .write(_Key, function (err) { if (err) { return handle(err); } if (!err) { // get the result of write var readPath = this.outname; var iniPath = this.outname.slice(4); var writePath = "dst".concat(iniPath); read(err, readPath, writePath, upload); } }); }; }; function read (err, readPath, writePath, callback) { // read file from temp directory fs.readFile(readPath, function (err, data) { if (err) { console.log("NO READY FILE FOR YOU!!!"); console.error(err); } callback(data, writePath); }); }; function upload (data, path) { // upload images to s3 bucket s3.putObject({ Bucket: srcBucket, Key: path, Body: data, ContentType: data.type }, function (err) { if (err) { console.error(err); } console.log("Uploaded with success!"); }); } download();
看看这个例子中他们如何使用Q.
你的代码最终会非常相似
download() .then(transform) .then(read) .then(upload) .catch(function (error) { // Handle any error from all above steps console.error(error); }) .done(function() { console.log('Finished processing image'); context.done(); });
你也可以看看asynchronous并使用它，就像在这个例子中显示的一样。