Firebase HTTP v1 API and no batch send anymore?

I received an email from Google informing me that the following service is being decommissioned:

"Including multiple send requests in a single HTTP request to FCM known as Batch Send."

The recommended approach is to:

"Send messages via the HTTP v1 API, which has been optimized for fanout performance."

On this page:

https://firebase.google.com/support/faq#fcm-23-deprecation

it is mentioned that:

https://fcm.googleapis.com/batch

"Requests to the endpoint will start failing after 6/21/2024."

The recommended action is to:

"Migrate to the standard HTTP v1 API send method, which supports HTTP/2 for multiplexing."

Now, I have a question regarding this matter.

Currently, I am sending FCM messages using PHP and cURL via fcm.googleapis.com/batch. Since this will no longer work next year, I have already discontinued this method and now I have put the message sending process in a foreach (while) loop. This means that if, for example, I send 400 FCM messages, I will trigger or contact the following URL 400 times in succession / row:

https://fcm.googleapis.com/v1/projects/my-app/messages:send

Is this the intended behavior and not a problem? My project already uses HTTP/2. I'm just wondering if this is the correct approach, as I can't imagine that it is better than sending in batches or all at once. Thank you for clarifying.

Please let me know if you need any further assistance.

Here my foreach code:

foreach ($deviceTokens as $token) {
  $data = json_encode(array(
    "message" => array(
      "token" => $token,
      "notification" => array(
        "message_title" => "Test",
        "message_body" => "Test", 
        "website_link" => "example.com", 
        "notification_type" => "message",
        "image" => "example.com/test.jpg"
      )      
    )
  ));

$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => 'https://fcm.googleapis.com/v1/projects/my-app/messages:send',
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => true,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => 'POST',
  CURLOPT_POSTFIELDS => $request,
  CURLOPT_HTTPHEADER => array(
    'Content-Type: multipart/mixed; boundary="subrequest_boundary"',
    'Authorization: Bearer ' . $accessToken 
  ),
));

$response = curl_exec($curl);
echo $response . '<br />';

curl_close($curl);
}

If you'd like to continue raw cURL requests, you could have a look at the asynchronous curl_multi_* functions - truth be told, it's been a while since I've used cURL directly, so I will just refer to the PHP docs which also provide a usage example that you could use as a template.

However, the way I would recommend to take is using the google/auth PHP Library, the Guzzle HTTP Client to authenticate and send requests to the FCM API, and Guzzle Promises to execute the requests asynchronously.

To make things "worse", you not only have to use the HTTP V1 endpoint, but the HTTP V1 FCM message format as well. The code below shows how the message in your original post would change.

So, here's how I would do it from scratch in a single script with the help of Composer:

# Initialize the project
mkdir myproject
cd myproject
composer require google/auth

<?php
# run.php

# This example uses Google Application Credentials exposed via the
# `GOOGLE_APPLICATION_CREDENTIALS` environment variable
# See https://github.com/googleapis/google-auth-library-php/blob/main/README.md
# for more alternative ways to authenticate requests

declare(strict_types=1);

require 'vendor/autoload.php';

use Google\Auth\ApplicationDefaultCredentials;
use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Promise;

### Create a Guzzle client that authenticates requests to the FCM API Endpoints

putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/credentials.json');

// https://developers.google.com/identity/protocols/oauth2/scopes#fcm
$scopes = [
    'https://www.googleapis.com/auth/cloud-platform',
    'https://www.googleapis.com/auth/firebase.messaging',
];

// create middleware
$middleware = ApplicationDefaultCredentials::getMiddleware($scopes);
$stack = HandlerStack::create();
$stack->push($middleware);

$client = new Client([
  'handler' => $stack,
  'auth' => 'google_auth'
]);

### Setup the messages

$deviceTokens = [/* ... */];
$messages = [];

foreach ($deviceTokens as $token) {
	$messages[] = [
		'token' => $token,
		'notification' => [
			'title' => 'Notification Title',
			'body' => 'Notification Body',
			'image' => 'https://example.com/test.jpg',
		],
		'webpush' => [
			'fcm_options' => [
				'link' => 'https://example.com'
			],
		],
	];
}

### Create message request promises

$promises = function() use ($client, $messages) {
	foreach ($messages as $message) {
		yield $client->requestAsync('POST', 'https://fcm.googleapis.com/v1/projects/my-app/messages:send', [
			'json' => ['message' => $message],
		]);
	}
};

### Create response handler

$handleResponses = function (array $responses) {
	foreach ($responses as $response) {
		if ($response['state'] === Promise\PromiseInterface::FULFILLED) {
			// $response['value'] is an instance of \Psr\Http\Message\RequestInterface
			echo $response['value']->getBody();
		} elseif ($response['state'] === Promise\PromiseInterface::REJECTED) {
			// $response['reason'] is an exception
			echo $response['reason']->getMessage();
		}
	}
};

Promise\Utils::settle($promises())
	->then($handleResponses)
	->wait();

I tested this script with one valid and one invalid registration token and got this result:

❯ php run.php
Client error: `POST https://fcm.googleapis.com/v1/projects/beste-firebase/messages:send` resulted in a `400 Bad Request` response:
{
  "error": {
    "code": 400,
    "message": "The registration token is not a valid FCM registration token",
    "stat (truncated...)
{
  "name": "projects/beste-firebase/messages/e39032c2-866d-4263-83e6-b1ce3770dfe6"
}

Or, if you don't want to do this all manually, you could also use the (unofficial) Firebase Admin PHP SDK, which switch to this exact approach
in its latest 7.5.0 release. (Disclaimer: I'm the maintainer and obviously biased):

# Initialize the project
mkdir myproject
cd myproject
composer require kreait/firebase-php

<?php
# run.php

# Again, this example uses Google Application Credentials exposed via the
# `GOOGLE_APPLICATION_CREDENTIALS` environment variable. The SDK picks
# them up automatically.

declare(strict_types=1);

require 'vendor/autoload.php';

use Kreait\Firebase\Factory;

### Initialize FCM
putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/credentials.json');
$fcm = (new Factory())->createMessaging();

### Setup the message (without target)

$deviceTokens = [/* ... */];
$message = [
    'notification' => [
        'title' => 'Notification Title',
        'body' => 'Notification Body',
        'image' => 'https://example.com/test.jpg',
    ],
    'webpush' => [
        'fcm_options' => [
            'link' => 'https://example.com'
        ],
    ],
];

### Send the message to the given tokens

$reports = $fcm->sendMulticast($message, $deviceTokens);

# https://firebase-php.readthedocs.io/en/stable/cloud-messaging.html#send-messages-to-multiple-devices-multicast
# goes more into detail what you can do with the reports

I hope this helps!