Google pub/sub subscription data doesn't match with the app - php

Question

I'm trying to listen for subscription changes (new and existing) of my Google Play app on the server. Here's the code I'm using. This uses the google/cloud-pubsub composer package:
$projectId = 'app-name';
$keyFile = file_get_contents(storage_path('app/app-name.json'));
$pubsub = new PubSubClient([
'projectId' => $projectId,
'keyFile' => json_decode($keyFile, true)
]);
$httpPostRequestBody = file_get_contents('php://input');
$requestData = json_decode($httpPostRequestBody, true);
info(json_encode($requestData));
$message = $pubsub->consume($requestData);
info(json_encode($message));
The code above works but the problem is that the data I get doesn't match the one I'm getting in the app side. This is a sample data:
{
"message":{
"data":"eyJ2ZXJ...",
"messageId":"16797998xxxxxxxxx",
"message_id":"1679799xxxxxxxxx",
"publishTime":"2020-12-15T02:09:23.27Z",
"publish_time":"2020-12-15T02:09:23.27Z"
},
"subscription":"projects\/app-name\/subscriptions\/test-subs"
}
If you base64_decode() the data, you'll get something like this:
{
version: "1.0",
packageName: "com.dev.app",
eventTimeMillis: "1607997631636",
subscriptionNotification: {
version: "1.0",
notificationType: 4,
purchaseToken: "kmloa....",
subscriptionId: "app_subs1"
}
}
This is where I'm expecting the purchaseToken to be the same as the one I'm getting from the client side.
Here's the code in the client-side. I'm using Expo in-app purchases to implement subscriptions:
setPurchaseListener(async ({ responseCode, results, errorCode }) => {
if (responseCode === IAPResponseCode.OK) {
const { orderId, purchaseToken, acknowledged } = results[0];
if (!acknowledged) {
await instance.post("/subscribe", {
order_id: orderId,
order_token: purchaseToken,
data: JSON.stringify(results[0]),
});
finishTransactionAsync(results[0], true);
alert(
"You're now subscribed! You can now use the full functionality of the app."
);
}
}
});
I'm expecting the purchaseToken I'm extracting from results[0] to be the same as the one the Google server is returning when it pushes the notification to the endpoint. But it doesn't.
Update
I think my main problem is that I'm assumming all the data I need will be coming from Google Pay, so I'm just relying on the data published by Google when a user subscribes in the app.
This isn't actually the one that publishes the message:
await instance.post("/subscribe")
It just updates the database with the purchase token. I can just use this to subscribe the user but there's no guarantee that the request is legitimate. Someone can just construct the necessary credentials based on an existing user and they can pretty much subscribe without paying anything. Plus this method can't be used to keep the user subscribed. So the data really has to come from Google.
Based on the answer below, I now realized that you're supposed to trigger the publish from your own server? and then you listen for that? So when I call this from the client:
await instance.post("/subscribe", {
purchaseToken
});
I actually need to publish the message containing the purchase token like so:
$pubsub = new PubSubClient([
'projectId' => $projectId,
]);
$topic = $pubsub->topic($topicName);
$message = [
'purchaseToken' => request('purchaseToken')
];
$topic->publish(['data' => $message]);
Is that what you're saying? But the only problem with this approach is how to validate if the purchase token is legitimate, and how to renew the subscription in the server? I have a field that needs to be updated each month so the user stays "subscribed" in the eyes of the server.
Maybe, I'm just overcomplicating things by using pub/sub. If there's actually an API which I could pull out data from regularly (using cron) which allows me to keep the user subscription data updated then that will also be acceptable as an answer.

Answer 1

First of all - I have a really bad experience with php and pubsub because of the php PubSubClient. If your script is only waiting for push and checking the messages then remove the pubsub package and handle it with few lines of code.
Example:
$message = file_get_contents('php://input');
$message = json_decode($message, true);
if (is_array($message)) {
$message = (isset($message['message']) && isset($message['message']['data'])) ? base64_decode($message['message']['data']) : false;
if (is_string($message)) {
$message = json_decode($message, true);
if (is_array($message)) {
$type = (isset($message['type'])) ? $message['type'] : null;
$data = (isset($message['data'])) ? $message['data'] : [];
}
}
}
I'm not sure how everything works on your side but if this part publishes the message:
await instance.post("/subscribe", {
order_id: orderId,
order_token: purchaseToken,
data: JSON.stringify(results[0]),
});
It looks like it's a proxy method to publish your messages. Because payload sent with it is not like a PubSub described schema and in the final message it doesn't look like IAPQueryResponse
If I was in your situation I will check few things to debug the problem:
How I publish/read a message to/from PubSub (topic, subscription and message payload)
I will write the publish mechanism as it is described in Google PubSub publish documentation
I will check my project, topic and subscription
If everything is set-up correctly then I will compare all other message data
If the problem persist then I will try to publish to PubSub minimal amount of data - just purchaseToken at the start to check what breaks the messages
For easier debug:
Create pull subscription
When you publish a message check pull subscription messages with "View messages"
For me the problem is not directly in PubSub but in your implementation of publish/receiving of messages.
UPDATE 21-12-2020:
Flow:
Customer create/renew subscription
Publish to pubsub with authentication
PubSub transfers the message to analysis application via "push" to make your analysis.
If you need information like:
New subscribers count
Renews count
Active subscriptions count
You can create your own analysis application but if you need something more complicated then you have to pick a tool to met your needs.
You can get the messages from pubsub also with "pull" but there are few cases I've met:
Last time I've used pull pubsub returns random amount of messages - if my limit is 50 and I have more than 50 messages in the queue I'm expecting to get 50 messages but sometimes pubsub gives me less messages.
PubSub returned messages in random order - now there is an option to use ordering key but it's something new.
To implement "pull" you have to run crons or something with "push" you receive the message as soon as possible.
With "pull" you have to depend on library/package (or whatever in any language it's called) but on "push" you can handle the message with just few lines of code as my php exapmle.