javascript - s3.getObject().createReadStream() : How to catch the error?

Question

I am trying to write a program to get a zip file from s3, unzip it, then upload it to S3. But I found two exceptions that I can not catch.

1. StreamContentLengthMismatch: Stream content length mismatch. Received 980323883 of 5770104761 bytes. This occurs irregularly.

2. NoSuchKey: The specified key does not exist. This happens when I input the wrong key.

When these two exceptions occur, this program crashes.

I'd like to catch and handle these two exceptions correctly.

I want to prevent a crash.

   const unzipUpload = () => {
        return new Promise((resolve, reject) => {
            let rStream = s3.getObject({Bucket: 'bucket', Key: 'hoge/hoge.zip'})
                .createReadStream()
                    .pipe(unzip.Parse())
                    .on('entry', function (entry) {
                        if(entry.path.match(/__MACOSX/) == null){

                            // pause
                            if(currentFileCount - uploadedFileCount > 10) rStream.pause()

                            currentFileCount += 1
                            var fileName = entry.path;
                            let up = entry.pipe(uploadFromStream(s3,fileName))

                            up.on('uploaded', e => {
                                uploadedFileCount += 1
                                console.log(currentFileCount, uploadedFileCount)

                                //resume
                                if(currentFileCount - uploadedFileCount <= 10) rStream.resume()

                                if(uploadedFileCount === allFileCount) resolve()
                                entry.autodrain()
                            }).on('error', e => {
                                reject()
                            })
                        }

                    }).on('error', e => {
                        console.log("unzip error")
                        reject()
                    }).on('finish', e => {
                        allFileCount = currentFileCount
                    })
            rStream.on('error', e=> {
                console.log(e)
                reject(e)
            })
        })
    }

    function uploadFromStream(s3,fileName) {
        var pass = new stream.PassThrough();

        var params = {Bucket: "bucket", Key: "hoge/unzip/" + fileName, Body: pass};
        let request = s3.upload(params, function(err, data) {
            if(err) pass.emit('error')
            if(!err) pass.emit('uploaded')
        })
        request.on('httpUploadProgress', progress => {
            console.log(progress)
        })

        return pass
    }

This is the library I use when unzipping. https://github.com/mhr3/unzip-stream

Help me!!

Answer 1

If you'd like to catch the NoSuchKey error thrown by createReadStream you have 2 options:

1. Check if key exists before reading it.
2. Catch error from stream

First:

s3.getObjectMetadata(key)
  .promise()
  .then(() => {
    // This will not throw error anymore
    s3.getObject().createReadStream();
  })
  .catch(error => {
    if (error.statusCode === 404) {
      // Catching NoSuchKey
    }
  });

The only case when you won't catch error if file was deleted in a split second, between parsing response from getObjectMetadata and running createReadStream

Second:

s3.getObject().createReadStream().on('error', error => {
    // Catching NoSuchKey & StreamContentLengthMismatch
});

This is a more generic approach and will catch all other errors, like network problems.