All notifications are resent after each reconnection

[dupuydauby]

Hello,

It seems that after a deconnection and reconnection: Connection to MCS server lost MCS socket closed after 49 minutes Trying to reconnect MCS client connected

I receive again all notifications since the beginning of the app.

In your blog you said you should have fixed it I think? But for now, I just skip them if they have already been received.

Tested on last version 1.2.0

[MatthieuLemoine]

That's weird because electron-push-receiver saves all the notification ids that has been received to avoid this issue.

The ids are saved using electron-config. You can see it using :

const Config = require('electron-config');
const persistentIds = config.get('persistentIds') 

console.log(persistentIds);

[dupuydauby]

Thanks for the feedback.

I understand that we have a list of notification Ids saved in order to avoid receiving twice the same notification.

But is this list also given at the reconnection if there is a deconnection to the MCS server? Or are the Ids of the list changing when we reconnect with same credentials?

[MatthieuLemoine]

For now the list is not sent when reconnecting so the client will receive all/some notifications again but they are filtered client side. Already received notifications are discarded by the client.

// Already received
if (persistentIds.includes(object.persistentId)) {
  return;
}

[PedroKantar]

I reproduce this issue: after losing connection all the notifications are resent, looks like persistentIds is lost. A candidate fix in push-receiver\src\client\socket\index.js would be to reload ```persistentIds" before performing the retry :

persistentIds = config.get('persistentIds') || [];

I'm going to test it...

[MatthieuLemoine]

I think I know why you have this issue.

In retry, we are using the persistentIds passed on the first connection attempt. So if new notifications are received during a connection, we will receive them again on subsequent retries.

How to reproduce :

• Connect
• Send a notification
• Disable internet connection
• Enable internet connection
• The notification is received again

Can you confirm this @PedroKantar and @dupuydauby ?

[MatthieuLemoine]

But you shouldn't receive all the notifications. Only those which have been received since the first connection attempt. All the previous notifications from previous sessions should not be received again.

[MatthieuLemoine]

The solution is simple, we just have to update the persistentIds array when we receive a new notification.

Should be done in push-receiver

[PedroKantar]

"Can you confirm this @PedroKantar and @dupuydauby ?" Yes I do. This exactly the sequence I observed, only the "delta" notifications between the last connect and the retry are received.

[PedroKantar]

@MatthieuLemoine : what do you think in this line , as a first candidate fix?

persistentIds = config.get('persistentIds') || [],

[MatthieuLemoine]

Well we don't have access to electron in push-receiver as it should work also in Node without electron.

A better way will be to update the persistentIds array on each notification here

persistentIds.push(object.persistentId);

[PedroKantar]

OK, my previous fix worked, but I did not catch the "should work also in Node without electron" point, I'm going to test your candidate.. And get back asap.

[PedroKantar]

It works!

[MatthieuLemoine]

Great ! Can you submit a PR on push-receiver @PedroKantar ?

[PedroKantar]

Yes!

[MatthieuLemoine]

Fixed in v1.2.2

[dupuydauby]

Thanks guys, working very well!