What happens if a user is on a poor connection that occasionally drops? Will they miss messages?

When a user is on a device that has a poor Internet connection, the connection to Pusher may occasionally be dropped. When they are not connected to Pusher any messages that were intended for them will not be delivered.

Dealing with poor Internet connectivity in your application

The Pusher client libraries expose connectivity through connection states. Your application can therefore detect any connectivity problems so that it is aware that it may have missed messages.

When the application becomes connected again you - which the app will be informed about through the connection state functionality - you can query the source of your data to see if you have missed any information. This can be done by keeping track of the last message you received and sending that (or a unique message identifier) as part of the query.

You may also be able to benefit from using Cache Channels.

When an event is triggered on a cache channel, Pusher Channels caches this event. Then when a client subscribes to a cache channel, if a cached value exists, it’s sent to the client as the first event on that channel. This behavior helps developers provide the initial state without adding additional logic to fetch it from elsewhere.

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