req.form.onPart not called when defined in a callback function

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I have a simple form, that sends multipart POST data to my Node.JS(v0.10.26) server, with Express(v3.1.2). This is the form:

<form id  =  "uploadForm"
enctype   =  "multipart/form-data"
action    =  "/upload"
method    =  "post">
<input type="file" name="userFile" />
<input type="submit" value="Upload File" name="submit">
</form>

On the server side, I am supposed to stream this file over to an S3 bucket. But before I do, I need to make sure that the bucket does not contain a file with the same name. So, I am getting a list of files present in the bucket and checking if a file with the same name exists.

handleUpload = function(req,res){
    console.log('Upload request.');

    var client = knox.createClient(s3AccessDetails);

    client.list({},function(err,fileListData){

        if(err){
            /* Handle error. */
        }

        else{
            if( fileListData.Contents.length == 0 ){
                fileListData = null;
            }
            console.log('Calling streamFile.');
            streamFile(req, res, fileListData, client);
        }

    });
}

I am over-riding the req.form.onPart in streamFile. streamFile is defined here.

var streamFile = function(req, res, fileListData, client){

    var i = 0;
    var errorObj = {};

    req.form.on('end',function(){
        console.log('Received end.');
        /*Handle end.*/
    });

    req.form.on('error',function(){
        console.log('Received error.');
        /*Handle error.*/
    });

    req.form.onPart = function(part){

        console.log('Received part.');

        if( part.filename != undefined ){

            console.log('On part.');

            if( fileListData != null ){
                /*Code to check if it is a duplicate file name.*/
                /*Iterate through fileListData and compare with part.filename.*/
                /*Handle a duplicate with appropriate error.*/
            }

            /* Else continue with the file streaming. */

            var headers = {};

            headers['Content-Length'] = req.headers['content-length'];

            console.log('Headers ' + JSON.stringify(req.headers));

            client.putStream(part, part.filename,headers,function(err,uploadresp){
                if(err){
                    console.log('Upload to s3 returned error. ' + err);
                    /* Handle error. */
                }
                else{

                    if( uploadresp == null || uploadresp == undefined){
                        console.log('Upload response is null.');
                        /* Handle error. */
                    }

                    console.log('S3 response code ' + uploadresp.statusCode);

                    res.statusCode = uploadresp.statusCode;
                    uploadresp.pipe(res);

                }
            })
        }
    }

    req.form.parse(req, function(error){
        console.log('In parse.');
        if(error){
            console.log('Parse error ' + error);
            /* Handle error. */
        }
    });

}

The problem I am facing is, the debug "console.log('Received part.');" is never seen! I tried this using files of size 1KB, 1MB and 15MB.

If I remove the call to client.list and call streamFile directly, this is working. But I need it to work in the callback for client.list. I'm using Knox(v0.9.2) to communicate with the S3 bucket.

This is how I have defined the middlwares in my express app.

app.use(express.json());
app.use(express.urlencoded());
app.use(express.multipart({ defer: true }));
app.use(express.methodOverride());
app.use(app.router);

This is my first question, apologies if I've gone wrong somewhere. Any leads appreciated!

asked 53 secs ago

the_kulk

1

req.form.onPart not called when defined in a callback function