Blog

Retrying an RPC Subscription with Web3.js 2.0

Using Web3.js 2.0, establishing a long-lived WebSocket connection can be a bit more challenging than in previous versions of the library. One common issue is reconnecting after a connection is dropped, which can lead to lost transactions or multiple data transmissions.

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

Why retry?

RPC (Remote Procedure Call) subscriptions allow you to execute blockchain functions remotely without having to worry about establishing a direct connection between the client and the server. However, as with all asynchronous operations, there is always the possibility of the connection being dropped or failing.

When a connection is dropped, your application may lose its position in the blockchain transactions in progress. As a result, all pending transactions may be sent multiple times, which can lead to wasted gas and loss of value.

Solution: Retry Mechanism

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

Here is an example of how you can modify your code to include retry:

const web3 = request('web3');
const { retry } = request('web3');
// Replace with the Web3.js provider URL
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 Web3 instance with your provider
const web3Instance = new web3(provider);
return web3Instance;
}
// Create an RPC subscription
async function createRpcSubscription() {
try {
const wsSubscription = await createWeb3RpcSubscription(
'0xYourPublicKey', // Your RPC endpoint
{ network: 'mainnet' } // Specify the blockchain network (e.g. mainnet, testnet)
);
console.log(RPC subscription created successfully!);
return wsSubscription;
} catch (error) {
if (error.message.includes('Disconnected')) {
// Retry after disconnecting
retry(error, 5);
}
console.error('Error creating RPC subscription:', error);
throw error;
}
}
// Main entry point of the application
async function main() {
const web3Instance = await connectToBlockchain();
const wsSubscription = await createRpcSubscription();
// Handle errors during connection
try {
console.log('Websocket connection established.');
} catch (error) {
throw error;
}
return wsSubscription;
}

How ​​it works:

• The “connectToBlockchain” function creates a new Web3 instance on the provider.

• The establishRpcSubscription function attempts to establish an RPC subscription using the created connection.

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

• Otherwise, if the connection is lost, the retry mechanism is triggered after a short delay (5 seconds) using the web3 retry function.

• Once the retries are exhausted or successful, the original error is rethrown.

Conclusion:

By implementing a retry mechanism like this, you can ensure that your Web3.js applications remain responsive and efficient even when dealing with blockchain transaction interruptions or errors. This approach helps minimize wasted gas and loss of value due to repeated retries.

Market Liquidation Order