go-waku/examples/filter2/README.md

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 obbject).
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.