gm aws lambda中的錯誤：string產生空緩衝區

Question

我試圖使用亞馬遜lambda進行自動定向轉換後將緩衝區上傳到s3。 我從API的NodeJS發送緩衝區像這樣：

var data = request.payload; 
 
      if (data.file) { 
 
      var Media = request.server.plugins.dogwater.media; 
 

 
      var name = data.file.hapi.filename; 
 
      var local_path = "./uploads/" + name; 
 
      var file = fs.createWriteStream(local_path); 
 
      console.log('adding media...') 
 
      file.on('error', function(err) { 
 
       console.error(err) 
 
      }); 
 

 
      data.file.pipe(file); 
 

 
      data.file.on('end', function(err) { 
 
       var pic = { 
 
       gallery_id: request.params.gallery_id, 
 
       type: 1 
 
       }; 
 
       console.log("\n\n\ndata.file = ",data.file) 
 
    
 
       Media.create(pic) 
 
       .then(function(media) { 
 
        httpRequest({ 
 
         url: 'secret', 
 
         method: 'POST', 
 
         json: { 
 
          media_id: media._id, 
 
          file_name: data.file.hapi.filename, 
 
          bucket: 'secret', 
 
          file: data.file 
 
         }, 
 
         headers: { 
 
         'x-api-key': 'someapikey' 
 
         }

當我控制檯登錄data.file._data在API我得到的東西，像這樣：

_data: <Buffer ff d8 ff e0 00 10 4a 46 49 46 00 01 01 01 00 48 00 48 00 00 ff e2 0b f8 49 43 43 5f 50 52 4f 46 49 4c 45 00 01 01 00 00 0b e8 00 00 00 00 02 00 00 00 ... >, 

在lambda（也nodejs）我有這樣的代碼：

// dependencies 
 
var async = require('async'); 
 
var AWS = require('aws-sdk'); 
 
var gm = require('gm').subClass({ 
 
    imageMagick: true 
 
}); 
 
var util = require('util'); 
 
var path = require('path'); 
 

 
// get reference to S3 client 
 
var s3 = new AWS.S3(); 
 
exports.handler = function(event, context) { 
 

 
    // payload data 
 
    var mediaId = event.media_id; 
 
    var filename = event.file_name; 
 
    var bucket = event.bucket; 
 
    var file = event.file._data; 
 

 
    console.log("file = ",file); 
 

 
    // Infer the image type. 
 
    var typeMatch = filename.match(/\.([^.]*)$/); 
 
    if (!typeMatch) { 
 
     console.error('unable to infer image type for file ' + filename); 
 
     return; 
 
    } 
 
    var imageType = typeMatch[1].toLowerCase(); 
 

 
    var acceptedTypes = ['jpg','gif','png','eps','jpeg']; 
 
    if (acceptedTypes.indexOf(imageType)===-1) { 
 
     console.log('skipping non-image '); 
 
     return; 
 
    } 
 

 

 
    async.waterfall([ 
 
     function process(next) { 
 
      // Transform the image buffer in memory. 
 
      gm(file).autoOrient().toBuffer(
 
       imageType.toUpperCase(), function(err, 
 
        buffer) { 
 
        if (err) { 
 
         //newly added line below: 
 
         console.log(err); 
 
         console.log("hit"); 
 
         next(err); 
 
        } else { 
 
         console.log("buffer = ",buffer); 
 
         next(null,buffer); 
 
        } 
 
       } 
 
      ); 
 
     }, 
 
     function upload(data, next) { 
 
      // Stream the image to folder. 
 
      s3.putObject({ 
 
       Bucket: bucket, 
 
       Key: mediaId + "/" + filename, 
 
       Body: data, 
 
       ContentType: imageType.toUpperCase() 
 
      }, next); 
 
     } 
 
     ], function(err, result) { 
 
      if (err) { 
 
       console.error(err); 
 
      } 
 
      // return data to api here 
 
      context.done(); 
 
     } 
 
    )// end async waterfall 
 
}// end exports handler

所以。當我嘗試上傳的圖像，這是什麼file._data打印爲GM命令之前：

{type:'Buffer',data:[234,234,234,random numbers etc ...]} 

但GM命令中的這個打印的錯誤：

Error: Stream yields empty buffer

Answer 1

發現了發出─

傳入aws lambda的數據必須重新映射到緩衝區對象才能被gm接受。代碼改變一行（內部exports.handler，在那裏我定義文件）

// dependencies 
 
var async = require('async'); 
 
var AWS = require('aws-sdk'); 
 
var gm = require('gm').subClass({ 
 
    imageMagick: true 
 
}); 
 
var util = require('util'); 
 
var path = require('path'); 
 

 
// get reference to S3 client 
 
var s3 = new AWS.S3(); 
 
exports.handler = function(event, context) { 
 

 
    // payload data 
 
    var mediaId = event.media_id; 
 
    var filename = event.file_name; 
 
    var bucket = event.bucket; 
 
    var file = new Buffer(event.file._data); 
 

 
    console.log("file = ",file); 
 

 
    // Infer the image type. 
 
    var typeMatch = filename.match(/\.([^.]*)$/); 
 
    if (!typeMatch) { 
 
     console.error('unable to infer image type for file ' + filename); 
 
     return; 
 
    } 
 
    var imageType = typeMatch[1].toLowerCase(); 
 

 
    var acceptedTypes = ['jpg','gif','png','eps','jpeg']; 
 
    if (acceptedTypes.indexOf(imageType)===-1) { 
 
     console.log('skipping non-image '); 
 
     return; 
 
    } 
 

 

 
    async.waterfall([ 
 
     function process(next) { 
 
      // Transform the image buffer in memory. 
 
      gm(file).autoOrient().toBuffer(
 
       imageType.toUpperCase(), function(err, 
 
        buffer) { 
 
        if (err) { 
 
         //newly added line below: 
 
         console.log(err); 
 
         console.log("hit"); 
 
         next(err); 
 
        } else { 
 
         console.log("buffer = ",buffer); 
 
         next(null,buffer); 
 
         //next(null, 'done'); 
 
        } 
 
       } 
 
      ); 
 
     }, 
 
     function upload(data, next) { 
 
      // Stream the image to folder. 
 
      s3.putObject({ 
 
       Bucket: bucket, 
 
       Key: mediaId + "/" + filename, 
 
       Body: data, 
 
       ContentType: imageType.toUpperCase() 
 
      }, next); 
 
     } 
 
     ], function(err, result) { 
 
      if (err) { 
 
       console.error(err); 
 
      } 
 
      // return data to api here 
 
      context.done(); 
 
     } 
 
    )// end async waterfall 
 
}// end exports handler