How to use gcs-resumable-upload with signed url

Question

I want to be able to do resumable uploads to Google Cloud Storage in a node.js client application using the gcs-resumable-upload package, in conjunction with signed urls (since the client app is invoked by unauthenticated users).

My server generates a signed url by calling getSignedUrl with {action: 'resumable'}. The server then sends a POST to the signed url with header { 'x-goog-resumable': 'start' } and an empty body, and receives a response with a location header that looks something like the following:

https://storage.googleapis.com/<bucket_name/<file_path>?GoogleAccessId=<service_account>&Expires=<expiry_time>&Signature=<signature>&upload_id=<upload_id>

My question is: If I return the above location header to my client, can the client use it to perform a resumable upload using gcs-resumable-upload, and if so, how exactly? If anyone has an example, that would be greatly appreciated!

Rakesh Choyal Rakesh Choyal · Accepted Answer · 2020-09-08T07:43:20

If you are using java then.

According to the google doc here It is clear how to create a signed URL to upload the object to a bucket.

But you need to add an extra header for resumable upload ("x-goog-resumable: start"). which is not mentioned in the doc.

import com.google.auth.oauth2.GoogleCredentials;
import com.google.auth.oauth2.ServiceAccountCredentials;
import com.google.cloud.storage.*;

import java.io.*;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

public class GenerateV4PutObjectSignedUrl {

    public static void generateV4GPutObjectSignedUrl(
            String projectId, String bucketName, String objectName) throws StorageException, IOException {
        File initialFile = new File("src/main/java/credentials.json");
        InputStream serviceAccountJson = new FileInputStream(initialFile);

        ServiceAccountCredentials credentials = (ServiceAccountCredentials)
                GoogleCredentials.fromStream(serviceAccountJson);
        Storage storage = StorageOptions.newBuilder().setProjectId(projectId).setCredentials(credentials).build().getService();

        // Define Resource
        BlobInfo blobInfo = BlobInfo.newBuilder(BlobId.of(bucketName, objectName)).build();

        // Generate Signed URL
        Map<String, String> header = new HashMap<>();
        header.put("x-goog-resumable", "start");

        URL url =
                storage.signUrl(
                        blobInfo,
                        15,
                        TimeUnit.MINUTES,
                        Storage.SignUrlOption.httpMethod(HttpMethod.POST),
                        Storage.SignUrlOption.withExtHeaders(header),
                        Storage.SignUrlOption.withV4Signature());


        System.out.println("Generated PUT signed URL:");
        System.out.println(url);
    }

    public static void main(String[] args) throws IOException {
        generateV4GPutObjectSignedUrl("projectId", "bucketName", "objectName");
    }
}

Use the generated URL to make a POST call. I used cURL for the request.
The response would something like this.

Host: storage.googleapis.com
> User-Agent: curl/7.54.0
> Accept: */*
> x-goog-resumable: start
>

< HTTP/2 201
< content-type: text/plain; charset=utf-8
< x-guploader-uploadid: some-id
< location: session URL for actual resumable upload
< content-length: 0
< date: Mon, 07 Sep 2020 12:18:00 GMT
< server: UploadServer

Now use the location to make a PUT call to upload the object. For more info on which headers to use on interruption see link

How to use gcs-resumable-upload with signed url

2 Answers