Request RPC subscription with Web3.js 2.0

When using Web3.js 2.0, establishing a long-term WebSocket connection can be a little more difficult than in earlier versions of the library. One of the common problems is reconnecting after disconnection, which can lead to the loss of transactions or repeated sending of data.

In this article, we will look at how to repeat an RPC subscription using Web3.js 2.0.

Why repeat?

RPC (Remote Procedure Call) subscriptions allow you to perform blockchain functions remotely without having to worry about establishing a direct connection between the client and the server. However, as with any asynchronous operation, there is always the possibility of a shutdown or failure.

When a shutdown occurs, your application may lose its position in the processed transactions of the block chain. As a result, it may resend all pending transactions multiple times, resulting in wasted gas and loss of value.

Solution: Mechanism of repetition

To solve this problem, we implement a retry mechanism using the built-in error handling functions of Web3.js 2.0. Our solution will use the retry function from the web3 package to automatically reconnect when necessary.

Here’s an example of how you can change the code to include repetition:

const web3 = require('web3');
const { retry } = require('web3');
// Replace with the URL of your Web3.js provider
const provider = new web3.providers.HttpProvider("
// Initialize the connection to the blockchain network
async function connectToBlockchain() {
const chainId = await web3.eth.getChainId();
console.log(Connected to blockchain ${chainId}...);
// Create a new instance of Web3 with your provider
const web3Instance = new web3(provider);
return web3Instance;
}
// Establish the RPC subscription
async function EstablishRpcSubscription() {
try {
const wsSubscription = await createWeb3RpcSubscription(
'0xYourPublicKey', // Your RPC endpoint
{ network: 'mainnet' } // Specify the blockchain network (for example, mainnet, testnet)
);
console.log(RPC subscription successfully established!);
return wsSubscription;
} catch (error) {
if (error.message.includes('Disconnected')) {
// Retry connection request after disconnection
retry(error, 5);
}
console.error('Error setting up RPC subscription:', error);
throw error;
}
}
// The main entry point for your application
async function main() {
const web3Instance = await connectToBlockchain();
const wsSubscription = await EstablishRpcSubscription();
// Handle any errors that occur during connection
try {
console.log('Websocket connection established.');
} catch (error) {
throw error;
}
return wsSubscription;
}

How ​​it works:

• The connectToBlockchain function establishes a new instance of Web3 with your provider.

• The installRpcSubscription function attempts to create an RPC subscription using the established connection.

• If the subscription is successfully created, it returns a newly created WebSocket object (wsSubscription).

• Otherwise, if a shutdown occurs, the replay mechanism is enabled after a short delay (5 seconds) using the `retry’ function from web3.

• After retries are exhausted or successful, the original error is re-issued.

Conclusion:

By implementing such a replay mechanism, you can ensure that your Web3.js applications remain responsive and efficient even when dealing with outages or failures in blockchain transactions. This approach also helps minimize gas wastage and cost due to repeats.

ETHEREUM OPENING FUTURES