filter2

Using the filter2 application

Background

The filter2 application is a basic example app that demonstrates how to subscribe to and publish messages using waku2-filter

Preparation

make

Basic application usage

To start the filter2 application run the following from the project directory

./build/filter2

The app will run 2 nodes ("full" node and "light" node), with light node subscribing to full node in order to receive filtered messages.

Flow description

Light Node

1. A light node is created with option WithWakuFilterLightNode.
2. Starting this node sets stream handler on wakunode.Host for WakuFilterProtocolId.
3. Light node submits a FilterSubscribeRequest through WakuFilterLightNode.Subscribe. This request is submitted to a particular peer. Filter is stored in WakuFilterLightNode.subscriptions map. That's it.
4. Now we wait on WakuFilterLightNode.onRequest to process any further messages.
5. On receiving a message check and notify all subscribers on relevant channel (which is part of subscription object).
6. If a broadcaster is specified, WakuNode.Subscribe has a message loop extracting WakuMessages from a wakurelay.Subscription object. It denotes a pubsub topic subscription. All envelopes are then submitted to node.broadcaster.

Full Node

1. Full node is created with option WithWakuFilterFullNode.
2. We read incoming messages in WithWakuFilterFullNode.onRequest(). It is set as a stream handler on wakunode.Host for WakuFilterProtocolId.
3. In WakuFilter.onRequest

• We check the type of FilterRequest and handle accordingly.
• If it's a FilterRequest for subscribe, add a subscriber.
• If it is a SubscriberPing request, check if subscriptions exists or not and respond accordingly.
• If it is an unsubscribe/unsubscribeAll request, check and remove relevant subscriptions.