Manage Your Filter Subscriptions

This guide provides detailed steps to manage Filter subscriptions and handle node disconnections in your application. Have a look at the Send and Receive Messages Using Light Push and Filter guide for using the Light Push and Filter protocols.

Overview

Occasionally, your Filter subscriptions might disconnect from the Waku Network, resulting in messages not being received by your application. To manage your subscriptions, periodically ping peers to check for an active connection. The error message "peer has no subscriptions" indicates a failed ping due to disconnection. You can stop the pings if the disconnection/unsubscription is deliberate.

Pinging filter subscriptions

The @waku/sdk package provides a Filter.ping() function to ping subscriptions and check for an active connection. To begin, create a Filter subscription:

// Create a Filter subscription
const { error, subscription } = await node.filter.createSubscription({ contentTopics: [contentTopic] });

if (error) {
    // handle errors if happens
    throw Error(error);
}

// Subscribe to content topics and process new messages
await subscription.subscribe([decoder], callback);

Next, create a function to ping and reinitiate the subscription:

const pingAndReinitiateSubscription = async () => {
    try {
        // Ping the subscription
        await subscription.ping();
    } catch (error) {
        if (
            // Check if the error message includes "peer has no subscriptions"
            error instanceof Error &&
            error.message.includes("peer has no subscriptions")
        ) {
            // Reinitiate the subscription if the ping fails
            await subscription.subscribe([decoder], callback);
        } else {
            throw error;
        }
    }
};

// Periodically ping the subscription
await pingAndReinitiateSubscription();

info

Pings will fail when there are temporary network degradations or reachability issues. This does not mean that the underlying connection has been closed.

Congratulations!

You have successfully managed your Filter subscriptions to handle node disconnections in your application.