amazon web services - How to determine if object exists AWS S3 Node.JS sdk

Question

I need to check if a file exists using AWS SDK. Here is what I'm doing:

var params = {
    Bucket: config.get('s3bucket'),
    Key: path
};

s3.getSignedUrl('getObject', params, callback);

It works but the problem is that when the object doesn't exists, the callback (with arguments err and url) returns no error, and when I try to access the URL, it says "NoSuchObject".

Shouldn't this getSignedUrl method return an error object when the object doesn't exists? How do I determine if the object exists? Do I really need to make a call on the returned URL?

Answer 1

Before creating the signed URL, you need to check if the file exists directly from the bucket. One way to do that is by requesting the HEAD metadata.

// Using callbacks
s3.headObject(params, function (err, metadata) {  
  if (err && err.code === 'NotFound') {  
    // Handle no object on cloud here  
  } else {  
    s3.getSignedUrl('getObject', params, callback);  
  }
});

// Using async/await (untested)
try { 
  const headCode = await s3.headObject(params).promise();
  const signedUrl = s3.getSignedUrl('getObject', params);
  // Do something with signedUrl
} catch (headErr) {
  if (headErr.code === 'NotFound') {
    // Handle no object on cloud here  
  }
}