Create Automation-Compatible Contracts

Learn how to make smart contracts that are compatible with Automation.

Automation Compatible Contracts

A contract is Automation-compatible when it follows a specified interface that allows the Chainlink Automation Network to determine if, when, and how the contract should be automated.

The interface you use will depend on the type of trigger you want to use:

• If you want a log event to trigger your upkeep, use the ILogAutomation interface.
• If you want to use on-chain state in a custom calculation to trigger your upkeep, use AutomationCompatibleInterface interface.
• If you want to call a function just based on time, you don't need an interface. Consider instead using a time-based upkeep.
• If you want to use Automation with Data Streams, use StreamsLookupCompatibleInterface interface.

You can learn more about these interfaces here.

Example Automation-compatible contract using custom logic trigger

Custom logic Automation compatible contracts must meet the following requirements:

• Import AutomationCompatible.sol. You can refer to the Chainlink Contracts on GitHub to find the latest version.
• Use the AutomationCompatibleInterface from the library to ensure your checkUpkeep and performUpkeep function definitions match the definitions expected by the Chainlink Automation Network.
• Include a checkUpkeep function that contains the logic that will be executed off-chain to see if performUpkeep should be executed. checkUpkeep can use on-chain data and a specified checkData parameter to perform complex calculations off-chain and then send the result to performUpkeep as performData.
• Include a performUpkeep function that will be executed on-chain when checkUpkeep returns true.

Use these elements to create a compatible contract that will automatically increment a counter after every updateInterval seconds. After you register the contract as an upkeep, the Chainlink Automation Network frequently simulates your checkUpkeep off-chain to determine if the updateInterval time has passed since the last increment (timestamp). When checkUpkeep returns true, the Chainlink Automation Network calls performUpkeep on-chain and increments the counter. This cycle repeats until the upkeep is cancelled or runs out of funding.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

// AutomationCompatible.sol imports the functions from both ./AutomationBase.sol and
// ./interfaces/AutomationCompatibleInterface.sol
import "@chainlink/contracts/src/v0.8/automation/AutomationCompatible.sol";

/**
 * @dev Example contract, use the Forwarder as needed for additional security.
 *
 * @notice important to implement {AutomationCompatibleInterface}
 */

/**
 * THIS IS AN EXAMPLE CONTRACT THAT USES HARDCODED VALUES FOR CLARITY.
 * THIS IS AN EXAMPLE CONTRACT THAT USES UN-AUDITED CODE.
 * DO NOT USE THIS CODE IN PRODUCTION.
 */

contract Counter is AutomationCompatibleInterface {
    /**
     * Public counter variable
     */
    uint256 public counter;

    /**
     * Use an interval in seconds and a timestamp to slow execution of Upkeep
     */
    uint256 public immutable interval;
    uint256 public lastTimeStamp;

    constructor(uint256 updateInterval) {
        interval = updateInterval;
        lastTimeStamp = block.timestamp;

        counter = 0;
    }

    function checkUpkeep(
        bytes calldata /* checkData */
    )
        external
        view
        override
        returns (bool upkeepNeeded, bytes memory /* performData */)
    {
        upkeepNeeded = (block.timestamp - lastTimeStamp) > interval;
        // We don't use the checkData in this example. The checkData is defined when the Upkeep was registered.
    }

    function performUpkeep(bytes calldata /* performData */) external override {
        if ((block.timestamp - lastTimeStamp) > interval) {
            lastTimeStamp = block.timestamp;
            counter = counter + 1;
        }
        // We don't use the performData in this example. The performData is generated by the Automation Node's call to your checkUpkeep function
    }
}

Compile and deploy your own Automation Counter onto a supported Testnet.

1. In the Remix example, select the compile tab on the left and press the compile button. Make sure that your contract compiles without any errors. Note that the Warning messages in this example are acceptable and will not block the deployment.
2. Select the Deploy tab and deploy the Counter smart contract in the injected web3 environment. When deploying the contract, specify the updateInterval value. For this example, set a short interval of 60. This is the interval at which the performUpkeep function will be called.
3. After deployment is complete, copy the address of the deployed contract. This address is required to register your upkeep in the Automation UI. The example in this document uses custom logic automation.

To see more complex examples, go to the Quick Starts page.

Now register your upkeep.

Vyper example

You can find a KeepersConsumer example here. Read the apeworx-starter-kit README to learn how to run the example.