Why does Web3j listen to events every 15 seconds?

Question

I use web3j in my Java application. In the smart contract, an event is defined.

 event sendEvent(string name);

I subscribed to that event in my app.

contract.sendEventEventFlowable(filter)
        .subscribe(doc -> {           
            System.out.println(doc.name);
        }, throwable -> {
            throwable.printStackTrace();
        }, () -> {
            System.out.println("End of research");
        });

It works, But I noticed that Web3j listens to the Blockchain every 15 seconds.

That is not suitable for my application and I need to listen to what is happening inside the blockchain all the time.

How can I change the default value (15 sec)?

This is my code

WebSocketService ws = new WebSocketService("ws://localhost:8545", true);
        ws.connect();
        web3 = Web3j.build(ws);

Answer 1

On ethereum mainnet a block is generated each 15 seconds. that is why 15 is the default value for events. however you can change this by using this build method:

    /**
     * Construct a new Web3j instance.
     *
     * @param web3jService web3j service instance - i.e. HTTP or IPC
     * @param pollingInterval polling interval for responses from network nodes
     * @param scheduledExecutorService executor service to use for scheduled tasks. <strong>You are
     *     responsible for terminating this thread pool</strong>
     * @return new Web3j instance
     */
    static Web3j build(
            Web3jService web3jService,
            long pollingInterval,
            ScheduledExecutorService scheduledExecutorService) {
        return new JsonRpc2_0Web3j(web3jService, pollingInterval, scheduledExecutorService);
    }

I found this in this issue about slow events https://github.com/web3j/web3j/issues/233 and the answer referenced to this method and link https://github.com/web3j/web3j/blob/master/core/src/main/java/org/web3j/protocol/Web3j.java#L17