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Blockchain Operation Errors

Blockchain Error Messages

The receipt for a FireFly blockchain operation contains an extraInfo section that records additional information about the transaction. For example:

"receipt": {
  ...
  "extraInfo": [
    {
      {
        "contractAddress":"0x87ae94ab290932c4e6269648bb47c86978af4436",
        "cumulativeGasUsed":"33812",
        "from":"0x2b1c769ef5ad304a4889f2a07a6617cd935849ae",
        "to":"0x302259069aaa5b10dc6f29a9a3f72a8e52837cc3",
        "gasUsed":"33812",
        "status":"0",
        "errorMessage":"Not enough tokens", 
      }
    }
  ],
  ...
},

The errorMessage field can be be set by a blockchain connector to provide FireFly and the end-user with more information about the reason why a tranasction failed. The blockchain connector can choose what information to include in errorMessage field. It may be set to an error message relating to the blockchain connector itself or an error message passed back from the blockchain or smart contract that was invoked.

Default Error Format With Hyperledger FireFly 1.3 and Hyperledger Besu 24.3.0

If FireFly is configured to connect to a Besu EVM client, and Besu has been configured with the revert-reason-enabled=true setting (note - the default value for Besu is false) error messages passed to FireFly from the blockchain client itself will be set correctly in the FireFly blockchain operation. For example:

  • "errorMessage":"Not enough tokens" for a revert error string from a smart contract

If the smart contract uses a custom error type, Besu will return the revert reason to FireFly as a hexadecimal string but FireFly will be unable to decode it into. In this case the blockchain operation error message and return values will be set to:

  • "errorMessage":"FF23053: Error return value for custom error: <revert hex string>
  • "returnValue":"<revert hex string>"

A future update to FireFly could be made to automatically decode custom error revert reasons if FireFly knows the ABI for the custom error. See FireFly issue 1466 which describes the current limitation.

If FireFly is configured to connect to Besu without revert-reason-enabled=true the error message will be set to:

  • "errorMessage":"FF23054: Error return value unavailable"

Error Retrieval Details

The precise format of the error message in a blockchain operation can vary based on different factors. The sections below describe in detail how the error message is populted, with specific references to the firefly-evmconnect blockchain connector.

Format of a firefly-evmconnect Error Message

The following section describes the way that the firefly-evmconnect plugin uses the errorMessage field. This serves both as an explanation of how EVM-based transaction errors will be formatted, and as a guide that other blockchain connectors may decide to follow.

The errorMessage field for a firefly-evmconnect transaction may contain one of the following:

  1. An error message from the FireFly blockchain connector
  2. For example "FF23054: Error return value unavailable"
  3. A decoded error string from the blockchain transaction
  4. For example Not enough tokens
  5. This could be an error string from a smart contract e.g. require(requestedTokens <= allowance, "Not enough tokens");
  6. An un-decoded byte string from the blockchain transaction
  7. For example 
    FF23053: Error return value for custom error: 0x1320fa6a00000000000000000000000000000000000000000000000000000000000000640000000000000000000000000000000000000000000000000000000000000010
  8. This could be a custom error from a smart contract e.g. 
    error AllowanceTooSmall(uint256 requested, uint256 allowance);
...
revert AllowanceTooSmall({ requested: 100, allowance: 20 });
  9. If an error reason cannot be decoded the returnValue of the extraInfo will be set to the raw byte string. For example: 
    "receipt": {
  ...
  "extraInfo": [
     {
       {
         "contractAddress":"0x87ae94ab290932c4e6269648bb47c86978af4436",
         "cumulativeGasUsed":"33812",
         "from":"0x2b1c769ef5ad304a4889f2a07a6617cd935849ae",
         "to":"0x302259069aaa5b10dc6f29a9a3f72a8e52837cc3",
         "gasUsed":"33812",
         "status":"0",
         "errorMessage":"FF23053: Error return value for custom error: 0x1320fa6a00000000000000000000000000000000000000000000000000000000000000640000000000000000000000000000000000000000000000000000000000000010", 
         "returnValue":"0x1320fa6a00000000000000000000000000000000000000000000000000000000000000640000000000000000000000000000000000000000000000000000000000000010"
       }
     }
  ],
  ...
},

Retrieving EVM Blockchain Transaction Errors

The ability of a blockchain connector such as firefly-evmconnect to retrieve the reason for a transaction failure, is dependent on by the configuration of the blockchain it is connected to. For an EVM blockchain the reason why a transaction failed is recorded with the REVERT op code, with a REASON set to the reason for the failure. By default, most EVM clients do not store this reason in the transaction receipt. This is typically to reduce resource consumption such as memory usage in the client. It is usually possible to configure an EVM client to store the revert reason in the transaction receipt. For example Hyperledger Besu™ provides the --revert-reason-enabled configuration option. If the transaction receipt does not contain the revert reason it is possible to request that an EVM client re-run the transaction and return a trace of all of the op-codes, including the final REVERT REASON. This can be a resource intensive request to submit to an EVM client, and is only available on archive nodes or for very recent blocks.

The firefly-evmconnect blockchain connector attempts to obtain the reason for a transaction revert and include it in the extraInfo field. It uses the following mechanisms, in this order:

  1. Checks if the blockchain transaction receipt contains the revert reason.
  2. If the revert reason is not in the receipt, and the connector.traceTXForRevertReason configuration option is set to true, calls debug_traceTransaction to obtain a full trace of the transaction and extract the revert reason. By default, connector.traceTXForRevertReason is set to false to avoid submitting high-resource requests to the EVM client.

If the revert reason can be obtained using either mechanism above, the revert reason bytes are decoded in the following way: - Attempts to decode the bytes as the standard Error(string) signature format and includes the decoded string in the errorMessage - If the reason is not a standard Error(String) error, sets the errorMessage to FF23053: Error return value for custom error: <raw hex string> and includes the raw byte string in the returnValue field.