Subscription Sharing

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Background

Ethereum JSON RPC subscriptions are a powerful feature that allows clients to receive real-time updates from the blockchain. Unlike http requests, subscriptions are not request-response based, and thus cannot be cached. Another reason they cannot be cached is that the data is constantly changing, and the client is only interested in the latest data in real-time.

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Introduction

Ethereum subscriptions present a unique challenge when multiple clients are interested in the same data, as each client would have to subscribe to the same data separately. This can lead to a high number of subscriptions, which can be expensive in terms of resources. Nexus solves this problem by sharing subscriptions across multiple clients, reducing the number of outbound subscriptions onto the node provider. Subscription sharing is enabled by default in Nexus, which automatically applies to newHeads and newPendingTransactions subscriptions.

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Configuration

Subscription sharing is enabled by default in Nexus, and can be disabled by setting the sharedSubscriptions.enabled option to false in the Nexus configuration. For more information on WebSocket configuration, see WebSockets.

const nexus = Nexus.create({
  sharedSubscriptions: {
    enabled: false
  }
  //...
});

const server = createServer(nexus);
nexus.ws(server);

server.listen(nexus.port, () => {
  nexus.logger.info(`🚀 Server ready at http://localhost:${nexus.port}`);
});