Debunking the Enigma: “Error: "execution reverted" when calling Chainlink Data Feed function in Remix on Polygon Cardano Testnet”

If you’re reading this, chances are you’ve stumbled upon the infamous “Error: "execution reverted"” message while attempting to call a Chainlink Data Feed function in Remix on the Polygon Cardano Testnet. Worry not, dear developer, for we’re about to embark on a journey to demystify this error and get your project back on track!

Understanding the Error

Before we dive into the solution, it’s essential to understand the root cause of the issue. The “Error: "execution reverted"” message is a generic error thrown by the Ethereum Virtual Machine (EVM) when a transaction reverts during execution. This can occur due to various reasons, including:

• Invalid or malformed contract code
• Insufficient gas provided for the transaction
• Reentrancy attacks or recursive function calls
• Unmatched or invalid function signatures
• Chainlink Data Feed function not properly configured

Prerequisites

Before we proceed, ensure you have the following setup:

• A Remix account and a Polygon Cardano Testnet project set up
• A Chainlink Data Feed contract deployed on the Polygon Cardano Testnet
• A basic understanding of Solidity and Remix

Troubleshooting Steps

Let’s go through a series of troubleshooting steps to identify and resolve the issue:

Step 1: Verify Contract Code

Review your contract code to ensure it’s correctly written and compiled. Pay attention to the following:

• Function signatures: Ensure they match the Chainlink Data Feed function signature
• Function implementation: Verify that the function is properly implemented and doesn’t contain any syntax errors
• Modifier usage: Check that modifiers, such as `onlyOwner`, are correctly used

pragma solidity ^0.8.0;

import "https://github.com/Chainlink/chainlink-external-adapter/blob/master/contracts/src/v0.8/ChainlinkClient.sol";

contract MyContract {
    address private oracle;
    bytes32 public jobId;
    uint256 public fee;

    constructor(address _oracle, bytes32 _jobId, uint256 _fee) {
        oracle = _oracle;
        jobId = _jobId;
        fee = _fee;
    }

    function requestPrice() public {
        // Verify function implementation and signature
        Chainlink.Request memory req = buildChainlinkRequest(jobId, address(this), this.fulfill.selector);
        req.add("get", "https://api.example.com/data");
        req.add("path", "price");
        req.addInt("times", 100);
        req.add("Multiplier", 1000);
        sendChainlinkRequestTo(oracle, req, fee);
    }

    function fulfill(bytes32 _requestId, uint256 _price) public recordChainlinkFulfillment(_requestId) {
        // Implement your logic here
    }
}

Step 2: Check Gas Provision

Ensure that you’re providing sufficient gas for the transaction. You can do this by:

• Increasing the gas limit for the transaction
• Optimizing your contract code to reduce gas consumption

// Increase gas limit for the transaction
tx.gas = 2000000;

Step 3: Verify Chainlink Data Feed Configuration

Double-check your Chainlink Data Feed configuration:

• Verify the oracle address and jobId
• Ensure the Chainlink node is properly configured and funded
• Check the data feed URL and path

// Verify Chainlink Data Feed configuration
address private oracle = 0x...;
bytes32 public jobId = "0x...";

// Verify Chainlink node configuration and funding
// ...

Step 4: Test Function Calls

Test individual function calls to isolate the issue:

• Call the Chainlink Data Feed function directly using Remix’s built-in debugger
• Verify that the function call returns the expected result

// Test Chainlink Data Feed function call
requestPrice();

Common Pitfalls and Solutions

Let’s address some common pitfalls and their solutions:

Pitfall 1: Unmatched Function Signatures

Solution:

// Ensure function signatures match
function requestPrice() public {
    // ...
}

function fulfill(bytes32 _requestId, uint256 _price) public {
    // ...
}

Pitfall 2: Insufficient Gas

Solution:

// Increase gas limit for the transaction
tx.gas = 2000000;

Pitfall 3: Chainlink Data Feed Misconfiguration

Solution:

// Verify Chainlink Data Feed configuration
address private oracle = 0x...;
bytes32 public jobId = "0x...";

// Verify Chainlink node configuration and funding
// ...

Conclusion

By following these troubleshooting steps and avoiding common pitfalls, you should be able to resolve the “Error: "execution reverted"” issue when calling the Chainlink Data Feed function in Remix on the Polygon Cardano Testnet. Remember to carefully review your contract code, gas provision, and Chainlink Data Feed configuration to ensure a seamless experience.

If you’re still facing issues, feel free to reach out to the Chainlink community or Remix support for further assistance.

Additional Resources

For further learning and troubleshooting, explore these resources:

• Chainlink VRF on Polygon
• Remix Documentation
• Chainlink External Adapter Repository

Troubleshooting Checklist
Verify contract code and compilation
Check gas provision and optimization
Verify Chainlink Data Feed configuration and node setup
Test individual function calls and isolate the issue

Happy debugging, and may the blockchain be with you!

Frequently Asked Question

Error "execution reverted" can be frustrating when working with Chainlink Data Feed function in Remix on Polygon Cardano Testnet. Here are some answers to commonly asked questions that might help you troubleshoot and resolve the issue: