How to determine if object exists AWS S3 Node.JS s

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

You can also use the waitFor method together with the state objectExists. This will use S3.headObject() internally.

var params = {
  Bucket: config.get('s3bucket'),
  Key: path
};
s3.waitFor('objectExists', params, function(err, data) {
  if (err) console.log(err, err.stack); // an error occurred
  else     console.log(data);           // successful response
});

Answer 2

Synchronous Put Operation

var request = require("request");
var AWS = require("aws-sdk");

AWS.config.update({
    accessKeyId: "*****",
    secretAccessKey: "***"
});


const s3 = new AWS.S3();


var response;

function initialize(bucket,key) {
    // Setting URL and headers for request
    const params = {
        Bucket: bucket,
        Key: key
    };
    // Return new promise 
    return new Promise(function(resolve, reject) {
        s3.putObject(params, function(err, resp, body) {  
            if (err) {  
                reject();
            } else {  
                resolve();
            }
          })
    })
}

function main() {

    var promiseArray = [];
    var prefix = 'abc/test/';
    for(var i=0;i<10;i++)
    {
        var key = prefix +'1234'+ i;
        promiseArray[i] = initialize('bucket',key);
        promiseArray[i].then(function(result) {
            console.log (" Successful ");
        }, function(err) {
            console.log (" Error ");
        });
    }


      console.log('Promises ' + promiseArray);


    Promise.all(promiseArray).then(function(values) {
        console.log("******TESTING****");
      });


}


main();

Answer 3

Use getObject method like this:

var params = {
    Bucket: config.get('s3bucket'),
    Key: path
};
s3.getObject(params, function(err, data){
    if(err) {
        console.log(err);
    }else {
      var signedURL = s3.getSignedUrl('getObject', params, callback);
      console.log(signedURL);
   }
});

Answer 4

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  
  }
}

Answer 5

Synchronous call on S3 in Nodejs instead of asynchronous call using Promise

var request = require("request");
var AWS = require("aws-sdk");

AWS.config.update({
    accessKeyId: "*****",
    secretAccessKey: "********"
});


const s3 = new AWS.S3();


var response;

function initialize(bucket,key) {
    // Setting URL and headers for request
    const params = {
        Bucket: bucket,
        Key: key
    };
    // Return new promise 
    return new Promise(function(resolve, reject) {
        s3.headObject(params, function(err, resp, body) {  
            if (err) {  
                console.log('Not Found : ' + params.Key );
                reject(params.Key);
            } else {  
                console.log('Found : ' + params.Key );
                resolve(params.Key);
            }
          })
    })
}

function main() {

    var foundArray = new Array();
    var notFoundArray = new Array();
    for(var i=0;i<10;i++)
    {
        var key = '1234'+ i;
        var initializePromise = initialize('****',key);
        initializePromise.then(function(result) {
            console.log('Passed for : ' + result);
            foundArray.push(result);
            console.log (" Found Array : "+ foundArray);
        }, function(err) {
            console.log('Failed for : ' + err);
            notFoundArray.push(err);
            console.log (" Not Found Array : "+ notFoundArray);
        });
    }


}

main();

Answer 6

by using headObject method

AWS.config.update({
        accessKeyId: "*****",
        secretAccessKey: "****",
        region: region,
        version: "****"
    });
const s3 = new AWS.S3();

const params = {
        Bucket: s3BucketName,
        Key: "filename" //if any sub folder-> path/of/the/folder.ext
}
try {
        await s3.headObject(params).promise()
        console.log("File Found in S3")
    } catch (err) {
        console.log("File not Found ERROR : " + err.code)
}

As params are constant, the best way to use it with const. If the file is not found in the s3 it throws the error NotFound : null.

If you want to apply any operations in the bucket, you have to change the permissions of CORS Configuration in the respective bucket in the AWS. For changing permissions Bucket->permission->CORS Configuration and Add this code.

<CORSConfiguration>
<CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>PUT</AllowedMethod>
    <AllowedMethod>POST</AllowedMethod>
    <AllowedMethod>DELETE</AllowedMethod>
    <AllowedMethod>GET</AllowedMethod>
    <AllowedMethod>HEAD</AllowedMethod>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>

for more information about CORS Configuration : https://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html