Using the StreamsLookup error handler

The Chainlink Automation StreamsLookup error handler provides insight into potential errors or edge cases in StreamsLookup upkeeps. The table below outlines a range of error codes and the behavior associated with the codes. Use the checkErrorHandler function to specify how you want to respond to the error codes. checkErrorHandler is simulated offchain and determines what action for Automation to take onchain in performUpkeep.

Error handler

When Automation detects an event, it runs the checkLog function, which includes a StreamsLookup revert custom error. The StreamsLookup revert enables your upkeep to fetch a report from Data Streams. If reports are fetched successfully, the checkCallback function is evaluated offchain. Otherwise, the checkErrorHandler function is evaluated offchain to determine what Automation should do next. Both of these functions have the same output types (bool upkeepNeeded, bytes memory performData), which Automation uses to run performUpkeep onchain. The example code also shows each function outlined in the diagram below:

If the Automation network fails to get the requested reports, an error code is sent to the checkErrorHandler function in your contract. If your contract doesn't have the checkErrorHandler function, nothing will happen. If your contract has the checkErrorHandler function, it is evaluated offchain to determine what to do next. For example, you could intercept or ignore certain errors and decide not to run performUpkeep in those cases, in order to save time and gas. For other errors, you can execute an alternative path within performUpkeep, and the upkeep runs the custom logic you define in your performUpkeep function to handle those errors.

1. Add the checkErrorHandler function in your contract to specify how you want to handle error codes. For example, you could decide to ignore any codes related to bad requests or incorrect input, without running performUpkeep onchain:

   /**
    * @notice Determines the need for upkeep in response to an error from Data Streams.
    * @param errorCode The error code returned by the Data Streams lookup.
    * @param extraData Additional context or data related to the error condition.
    * @return upkeepNeeded Boolean indicating whether upkeep is needed based on the error.
    * @return performData Data to be used if upkeep is performed, encoded with success state and error context.
    */
   function checkErrorHandler(
     uint errorCode,
     bytes calldata extraData
   ) external returns (bool upkeepNeeded, bytes memory performData) {
     // Add custom logic to handle errors offchain here
     bool _upkeepNeeded = true;
     bool reportSuccess = false;
     if (errorCode == 808400) {
       // Handle bad request errors code offchain.
       // In this example, no upkeep needed for bad request errors.
       _upkeepNeeded = false;
     } else {
       // Handle other errors as needed.
     }
     return (_upkeepNeeded, abi.encode(reportSuccess, abi.encode(errorCode, extraData)));
   }
   

2. Define custom logic for the alternative path within performUpkeep, to handle any error codes you did not intercept offchain in checkErrorHandler:

   // function will be performed on-chain
   function performUpkeep(bytes calldata performData) external {
     // Decode incoming performData
     (bool reportSuccess, bytes memory payload) = abi.decode(performData, (bool, bytes));
   
     if (reportSuccess) {
       // Decode the performData bytes passed in by CL Automation.
       // This contains the data returned by your implementation in checkCallback().
       (bytes[] memory signedReports, bytes memory extraData) = abi.decode(payload, (bytes[], bytes));
       // Logic to verify and decode report
       // ...
     } else {
       // Handle error condition
       (uint errorCode, bytes memory extraData) = abi.decode(payload, (uint, bytes));
       // Custom logic to handle error codes
     }
   }
   

Testing checkErrorHandler

checkErrorHandler is simulated offchain. When upkeepNeeded returns true, Automation runs performUpkeep onchain using the performData from checkErrorHandler. If the checkErrorHandler function itself reverts, performUpkeep does not run.

If you need to force errors in StreamsLookup while testing, you can try the following methods:

• Not specifying any feedID to force error code 808400 (ErrCodeStreamsBadRequest)
• Specifying an incorrect feedID to force error code 808401 (ErrCodeStreamsBadRequest)
• Specifying a future timestamp to force error code 808206 (where partial content is received) for both single feedID and bulk feedID requests
• Specifying old timestamps for reports not available anymore yields either error code 808504 (no response) or 808600 (bad response), depending on which service calls the timeout request

If your StreamsLookup revert function is defined incorrectly in your smart contracts, the nodes will not be able to decode it.

Error codes

Example code

This example code includes the revert StreamsLookup, checkCallback, checkErrorHandler and performUpkeep functions. The full code example is available here.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

import {StreamsLookupCompatibleInterface} from "@chainlink/contracts/src/v0.8/automation/interfaces/StreamsLookupCompatibleInterface.sol";
import {ILogAutomation, Log} from "@chainlink/contracts/src/v0.8/automation/interfaces/ILogAutomation.sol";
import {IRewardManager} from "@chainlink/contracts/src/v0.8/llo-feeds/interfaces/IRewardManager.sol";
import {IVerifierFeeManager} from "@chainlink/contracts/src/v0.8/llo-feeds/interfaces/IVerifierFeeManager.sol";
import {IERC20} from "@chainlink/contracts/src/v0.8/vendor/openzeppelin-solidity/v4.8.3/contracts/interfaces/IERC20.sol";
import {Common} from "@chainlink/contracts/src/v0.8/llo-feeds/libraries/Common.sol";

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

// =====================
// INTERFACES
// =====================

interface IFeeManager {
    /**
     * @notice Calculates the fee and reward associated with verifying a report, including discounts for subscribers.
     * This function assesses the fee and reward for report verification, applying a discount for recognized subscriber addresses.
     * @param subscriber The address attempting to verify the report. A discount is applied if this address
     * is recognized as a subscriber.
     * @param unverifiedReport The report data awaiting verification. The content of this report is used to
     * determine the base fee and reward, before considering subscriber discounts.
     * @param quoteAddress The payment token address used for quoting fees and rewards.
     * @return fee The fee assessed for verifying the report, with subscriber discounts applied where applicable.
     * @return reward The reward allocated to the caller for successfully verifying the report.
     * @return totalDiscount The total discount amount deducted from the fee for subscribers.
     */
    function getFeeAndReward(
        address subscriber,
        bytes memory unverifiedReport,
        address quoteAddress
    ) external returns (Common.Asset memory, Common.Asset memory, uint256);

    function i_linkAddress() external view returns (address);

    function i_nativeAddress() external view returns (address);

    function i_rewardManager() external view returns (address);
}

interface IVerifierProxy {
    /**
     * @notice Verifies that the data encoded has been signed.
     * correctly by routing to the correct verifier, and bills the user if applicable.
     * @param payload The encoded data to be verified, including the signed
     * report.
     * @param parameterPayload Fee metadata for billing. In the current implementation,
     * this consists of the abi-encoded address of the ERC-20 token used for fees.
     * @return verifierResponse The encoded report from the verifier.
     */
    function verify(
        bytes calldata payload,
        bytes calldata parameterPayload
    ) external payable returns (bytes memory verifierResponse);

    function s_feeManager() external view returns (IVerifierFeeManager);
}

// ==========================
// CONTRACT IMPLEMENTATION
// ==========================

contract StreamsUpkeepWithErrorHandler is
    ILogAutomation,
    StreamsLookupCompatibleInterface
{
    struct Report {
        bytes32 feedId; // The feed ID the report has data for
        uint32 validFromTimestamp; // Earliest timestamp for which price is applicable
        uint32 observationsTimestamp; // Latest timestamp for which price is applicable
        uint192 nativeFee; // Base cost to validate a transaction using the report, denominated in the chain’s native token (WETH/ETH)
        uint192 linkFee; // Base cost to validate a transaction using the report, denominated in LINK
        uint32 expiresAt; // Latest timestamp where the report can be verified on-chain
        int192 price; // DON consensus median price, carried to 18 decimal places
        int192 bid; // Simulated price impact of a buy order up to the X% depth of liquidity utilisation
        int192 ask; // Simulated price impact of a sell order up to the X% depth of liquidity utilisation
    }

    struct Quote {
        address quoteAddress;
    }

    event PriceUpdate(int192 indexed price);
    event ErrorTestLog(uint indexed errorCode);

    IVerifierProxy public verifier;

    address public FEE_ADDRESS;
    string public constant STRING_DATASTREAMS_FEEDLABEL = "feedIDs";
    string public constant STRING_DATASTREAMS_QUERYLABEL = "timestamp";
    uint256 public s_error;
    bool public s_isError;
    string[] public feedIds = [
        "0x000359843a543ee2fe414dc14c7e7920ef10f4372990b79d6361cdc0dd1ba782" // Ex. ETH/USD Feed ID
    ];

    constructor(address _verifier) {
        verifier = IVerifierProxy(_verifier); //Arbitrum Sepolia: 0x2ff010debc1297f19579b4246cad07bd24f2488a
    }

    // This function uses revert to convey call information.
    // See https://eips.ethereum.org/EIPS/eip-3668#rationale for details.
    function checkLog(
        Log calldata log,
        bytes memory
    ) external returns (bool upkeepNeeded, bytes memory performData) {
        revert StreamsLookup(
            STRING_DATASTREAMS_FEEDLABEL,
            feedIds,
            STRING_DATASTREAMS_QUERYLABEL,
            log.timestamp,
            ""
        );
    }

    /**
     * @dev This function is intended for off-chain simulation by Chainlink Automation to pass in the data reports fetched from Data Streams.
     * @param values The bytes array of data reports fetched from Data Streams.
     * @param extraData Contextual or additional data related to the feed lookup process.
     * @return upkeepNeeded Indicates that upkeep is needed to pass the data to the on-chain performUpkeep function.
     * @return performData Encoded data indicating success and including the original `values` and `extraData`, to be used in `performUpkeep`.
     */
    function checkCallback(
        bytes[] calldata values,
        bytes calldata extraData
    ) external pure returns (bool upkeepNeeded, bytes memory) {
        bool reportSuccess = true; // Indicates successful data retrieval
        return (true, abi.encode(reportSuccess, abi.encode(values, extraData)));
    }

    /**
     * @notice Determines the need for upkeep in response to an error from Data Streams.
     * @dev This function serves as an example of how errors can be handled offchain.
     * @dev Developers can parameterize this logic as needed.
     * @dev All error codes are documented at: https://docs.chain.link/chainlink-automation/guides/streams-lookup-error-handler#error-codes
     * @param errorCode The error code returned by the Data Streams lookup.
     * @param extraData Additional context or data related to the error condition.
     * @return upkeepNeeded Boolean indicating whether upkeep is needed based on the error.
     * @return performData Data to be used if upkeep is performed, encoded with success state and error context.
     */
    function checkErrorHandler(
        uint errorCode,
        bytes calldata extraData
    ) external view returns (bool upkeepNeeded, bytes memory performData) {
        bool _upkeepNeeded = false;
        bool reportSuccess = false;
        if (errorCode == 0) {
            // If there is no error, proceed with the performUpkeep and
            // the report decoding/verification
            _upkeepNeeded = true;
            reportSuccess = true;
        } else if (errorCode == 808400 || errorCode == 808401) {
            // Mark upkeep as needed for bad requests (808400) and incorrect feed ID (808401)
            // to handle these specific errors onchain.
            _upkeepNeeded = true;
            // Note that reportSuccess remains false.
        } else {
            // For other error codes, decide not to perform upkeep.
            // This is the default behavior, explicitly noted for clarity in this example.
            _upkeepNeeded = false;
            reportSuccess = false;
        }
        return (
            _upkeepNeeded,
            abi.encode(reportSuccess, abi.encode(errorCode, extraData))
        );
    }

    function performUpkeep(bytes calldata performData) external {
        // Decode incoming performData
        (bool reportSuccess, bytes memory payload) = abi.decode(
            performData,
            (bool, bytes)
        );

        if (reportSuccess) {
            // Decode the performData bytes passed in by CL Automation.
            // This contains the data returned by your implementation in checkCallback().
            (bytes[] memory signedReports, bytes memory extraData) = abi.decode(
                payload,
                (bytes[], bytes)
            );
            // Logic to verify and decode report
            bytes memory unverifiedReport = signedReports[0];

            (, bytes memory reportData) = abi.decode(
                unverifiedReport,
                (bytes32[3], bytes)
            );

            // Report verification fees
            IFeeManager feeManager = IFeeManager(
                address(verifier.s_feeManager())
            );
            IRewardManager rewardManager = IRewardManager(
                address(feeManager.i_rewardManager())
            );

            address feeTokenAddress = feeManager.i_linkAddress();
            (Common.Asset memory fee, , ) = feeManager.getFeeAndReward(
                address(this),
                reportData,
                feeTokenAddress
            );

            // Approve rewardManager to spend this contract's balance in fees
            IERC20(feeTokenAddress).approve(address(rewardManager), fee.amount);

            // Verify the report
            bytes memory verifiedReportData = verifier.verify(
                unverifiedReport,
                abi.encode(feeTokenAddress)
            );

            // Decode verified report data into BasicReport struct
            Report memory verifiedReport = abi.decode(
                verifiedReportData,
                (Report)
            );

            // Log price from report
            emit PriceUpdate(verifiedReport.price);
        } else {
            // Handle error condition
            (uint errorCode, bytes memory extraData) = abi.decode(
                payload,
                (uint, bytes)
            );
            // Custom logic to handle error codes
            s_error = errorCode;
            s_isError = true;
        }
    }

    fallback() external payable {}

    receive() external payable {}
}