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Use Case: Reactive Network Demo

Overview​

This article focuses on building and deploying a reactive contract, using the basic Reactive Network Demo that provides:

  • Low-latency monitoring of logs emitted by contracts on the origin chain (Sepolia testnet).
  • Executing calls from the Reactive Network to contracts on the destination chain, also on Sepolia.

Basic Demo Smart Contract

Contracts​

Origin Chain Contract: BasicDemoL1Contract receives Ether and returns it to the sender, emitting a Received event with transaction details.

Reactive Contract: BasicDemoReactiveContract demonstrates a reactive subscription model on Ethereum Sepolia. It listens for logs from a specified contract and emits an Event for each incoming log while incrementing a local counter. If the incoming log’s topic_3 value is at least 0.01 Ether, it emits a Callback event containing a payload to invoke a callback function externally.

function react(LogRecord calldata log) external vmOnly {
    emit Event(
        log.chain_id,
        log._contract,
        log.topic_0,
        log.topic_1,
        log.topic_2,
        log.topic_3,
        log.data,
        ++counter
    );

    if (log.topic_3 >= 0.01 ether) {
        bytes memory payload = abi.encodeWithSignature("callback(address)", address(0));
        emit Callback(log.chain_id, _callback, GAS_LIMIT, payload);
    }
}

Destination Chain Contract: BasicDemoL1Callback logs callback details upon receiving a call, capturing the origin, sender, and reactive sender addresses. It could also be a third-party contract.

Further Considerations​

The demo highlights just a subset of Reactive Network's features. Potential improvements include:

  • Enhanced Event Subscriptions: Subscribing to multiple event origins, including callback logs, to maintain consistency.
  • Dynamic Subscriptions: Allowing real-time adjustments to subscriptions based on conditions.
  • State Management: Introducing persistent state handling for more complex, context-aware reactions.
  • Flexible Callbacks: Supporting arbitrary transaction payloads to increase adaptability.

Deployment​

To deploy the contracts to Ethereum Sepolia and Reactive Kopli, clone the project and follow the Deployment & Testing steps. Replace the relevant keys, addresses, and endpoints as needed. Make sure all environment variables are correctly configured before proceeding.

Conclusion​

In this article, we explored how reactive contracts operate and deployed a simple system using one. We examined the process step by step, including event emission, tracking, and performing post-actions on the destination Ethereum contract through the reactive one. While this example doesn't include practical logic, it demonstrates the technology's functionality and sets the stage for real-world applications.