App Engine Backend with Google Cloud Messaging sending message to more than 1000 users

Question

I want to send a message (e.g. Update available) to all users(~15,000). I have implemented App Engine Backend with Google Cloud Messaging to send message.

I have tested on 2 devices. Got message on both. But as google docs says "GCM is support for up to 1,000 recipients for a single message."

My question is how to send same message to remaining 14,000 users in my case? Or the code below will take care of it?

Below is the code which sends message

import com.google.android.gcm.server.Constants;
import com.google.android.gcm.server.Message;
import com.google.android.gcm.server.Result;
import com.google.android.gcm.server.Sender;
import com.google.api.server.spi.config.Api;
import com.google.api.server.spi.config.ApiNamespace;

import java.io.IOException;
import java.util.List;
import java.util.logging.Logger;

import javax.inject.Named;

import static com.example.shani.myapplication.backend.OfyService.ofy;

/**
 * An endpoint to send messages to devices registered with the backend
 * <p/>
 * For more information, see
 * https://developers.google.com/appengine/docs/java/endpoints/
 * <p/>
 * NOTE: This endpoint does not use any form of authorization or
 * authentication! If this app is deployed, anyone can access this endpoint! If
 * you'd like to add authentication, take a look at the documentation.
 */
@Api(name = "messaging", version = "v1", namespace = @ApiNamespace(ownerDomain = "backend.myapplication.shani.example.com", ownerName = "backend.myapplication.shani.example.com", packagePath = ""))
public class MessagingEndpoint {
    private static final Logger log = Logger.getLogger(MessagingEndpoint.class.getName());

    /**
     * Api Keys can be obtained from the google cloud console
     */
    private static final String API_KEY = System.getProperty("gcm.api.key");

    /**
     * Send to the first 10 devices (You can modify this to send to any number of devices or a specific device)
     *
     * @param message The message to send
     */
    public void sendMessage(@Named("message") String message) throws IOException {
        if (message == null || message.trim().length() == 0) {
            log.warning("Not sending message because it is empty");
            return;
        }
        // crop longer messages
        if (message.length() > 1000) {
            message = message.substring(0, 1000) + "[...]";
        }
        Sender sender = new Sender(API_KEY);

         Message msg = new Message.Builder().addData("message", message).build();

        List<RegistrationRecord> records = ofy().load().type(RegistrationRecord.class).limit(1000).list();
        for (RegistrationRecord record : records) {
            Result result = sender.send(msg, record.getRegId(), 5);
            if (result.getMessageId() != null) {
                log.info("Message sent to " + record.getRegId());
                String canonicalRegId = result.getCanonicalRegistrationId();
                if (canonicalRegId != null) {
                    // if the regId changed, we have to update the datastore
                    log.info("Registration Id changed for " + record.getRegId() + " updating to " + canonicalRegId);
                    record.setRegId(canonicalRegId);
                    ofy().save().entity(record).now();
                }
            } else {
                String error = result.getErrorCodeName();
                if (error.equals(Constants.ERROR_NOT_REGISTERED)) {
                    log.warning("Registration Id " + record.getRegId() + " no longer registered with GCM, removing from datastore");
                    // if the device is no longer registered with Gcm, remove it from the datastore
                    ofy().delete().entity(record).now();
                } else {
                    log.warning("Error when sending message : " + error);
                }
            }
        }
    }
}

I know there are simillar questions but I am using Java language. I found questions which uses php language at backend. so not helpful to me!

1. Google Cloud Messaging: Send message to "all" users
2. Sending Push Notification on multiple devices

Is there anyone who has successfully implemented App Engine+Google Cloud Messaging JAVA language?

In the below code line if I replace 1000 with 15,000 Will it solve my problem?

List<RegistrationRecord> records = ofy().load().type(RegistrationRecord.class).limit(1000).list();

Please please help as soon as possible. And very sorry for my English.. If anyone need other details you are welcome to ask.

Thanks for your time.

Answer 1

A few considerations,

1) Sending notifications to a possibly huge number of users might take significant time, consider using Task Queues to queue that work to be done "offline" outside the 60 sec limit.

2) Now as for the GCM limit, if you need to all your users but GCM allow you 1000 at a time just split them in batches of 1000 and send every batch a message separately.

If you combine both recommendations you should have a fairly scalable process where you query for all your users in 1 request , split that list and just queue sending the message to those users 1000 at a time.

Answer 2

Extension to the @jirungaray answer below is code for sending GCM messages to all registered users,

Here I assume that from android you are registering each mobile-devices for GCM services and storing those device tokens in database.

public class GCM {
    private final static Logger LOGGER = Logger.getLogger(GCM.class.getName());
    private static final String API_KEY = ConstantUtil.GCM_API_KEY;
    public static void doSendViaGcm(List<String> tocken,String message) throws IOException {
        Sender sender = new Sender(API_KEY);
    // Trim message if needed.
    if (message.length() > 1000) {
      message = message.substring(0, 1000) + "[...]";
     }
     Message msg = new Message.Builder().addData("message", message).build();
    try{
    MulticastResult result = sender.send(msg, tocken, 5);
    }catch(Exception ex){
    LOGGER.severe("error is"+ex.getMessage());
    ex.printStackTrace();
    }
}

}

In above code snippet API_KEY can be obtain from google console project ,here I assume that you have already created one google console project and enable GCM api,

you can generate API_KEY as follows

your_google_console_project>> Credentials>> Create New Key >> Server key >> enter ip address Which you want to allow access to GCM api[i used 0.0.0.0/0]

Now doSendViaGcm(List tocken,String message) of GCM class performs task of sending messages to all register android mobile devices

here List<String> token is array-list of all device token on which messages will be delivered ,remember this list size should not more than 1000 or else http call will fail.

hope this will help you thanks