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.

Contracts

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

• Reactive Contract: BasicDemoReactiveContract subscribes to events on Sepolia, emits logs, and triggers callbacks when conditions are met, such as topic_3 being at least 0.1 Ether. It manages event subscriptions and tracks processed events.

function react(
    uint256 chain_id,
    address _contract,
    uint256 topic_0,
    uint256 topic_1,
    uint256 topic_2,
    uint256 topic_3,
    bytes calldata data,
    uint256 /* block_number */,
    uint256 /* op_code */
) external vmOnly {
    emit Event(chain_id, _contract, topic_0, topic_1, topic_2, topic_3, data, ++counter);
    if (topic_3 >= 0.1 ether) {
        bytes memory payload = abi.encodeWithSignature("callback(address)", address(0));
        emit Callback(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.