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This guide provides practical instructions for interacting with the Contract Manager module, including handling failures and resubmitting failed operations.

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Handling IBC Acknowledgments in Smart Contracts

When developing contracts that use IBC functionality on Neutron, you need to properly handle acknowledgments: 
// Example of a proper IBC acknowledgment handler in CosmWasm
#[entry_point]
pub fn sudo(deps: DepsMut, env: Env, msg: SudoMsg) -> Result<Response, ContractError> {
    match msg {
        SudoMsg::Response { request, data } => {
            // Store the data instead of processing it immediately
            PENDING_RESPONSES.save(deps.storage, &data)?;
            
            // Return success - failures will be captured by Contract Manager
            Ok(Response::new().add_attribute("action", "response_received"))
        },
        _ => Err(ContractError::UnknownSudoMsg {}),
    }
}

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Best Practices

  1. Keep Sudo Handlers Light: Due to gas limitations, sudo handlers should only store data without complex processing
  2. Separate Processing Logic: Use separate execute messages to process the stored data
  3. Handle All Message Types: Implement handlers for all expected sudo message types
  4. Prepare for Resubmission: Design your contract to handle potential resubmission of messages

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Checking for Contract Failures

To check if your contract has experienced any failures, you can use the Contract Manager query functionality:

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Using CLI

neutrond query contractmanager failures [contract-address]
Example output: 
{
  "failures": [
    {
      "address": "neutron1...",
      "id": "1",
      "error": "codespace: wasm, code: 5",
      "sudo_payload": "..."
    }
  ]
}

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Via CosmWasm Contract

You can query failures from within another contract using bindings: 
// Query failures from a CosmWasm contract
pub fn query_failures(
    querier: &QuerierWrapper,
    contract_address: String,
) -> StdResult<FailuresResponse> {
    let request = NeutronQuery::ContractManagerFailures { 
        address: contract_address,
        pagination: None,
    };
    
    querier.query(&QueryRequest::Custom(request))
}

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Getting Detailed Failure Information

For more detailed error information (beyond the redacted error in state): 
neutrond query contractmanager failure-details [address] [failure_id]
Note: This query requires a node that indexes transactions and still has the relevant blocks available.

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Resubmitting Failed Operations

If your contract experiences a failure due to gas limits or other temporary issues, you can resubmit the operation:

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Using CosmWasm Bindings

// Example of resubmitting a failed operation
pub fn resubmit_failure(
    deps: DepsMut,
    env: Env,
    failure_id: u64,
) -> Result<Response, ContractError> {
    // Create the resubmit message
    let resubmit_msg = NeutronMsg::ResubmitFailure { 
        failure_id,
    };
    
    // Return a response with the message
    Ok(Response::new()
        .add_message(resubmit_msg)
        .add_attribute("action", "resubmit_failure")
        .add_attribute("failure_id", failure_id.to_string()))
}
Important rules for resubmission:
  1. Only the original contract that received the IBC message can resubmit the failure
  2. Resubmission still runs with the same sudo gas limit constraints as the original call
  3. You should fix any issues in your contract before resubmitting (e.g., optimize gas usage or simplify logic)
If your contract failed due to running out of gas within the sudo gas limit, simply resubmitting will likely fail again. You must either optimize your contract’s sudo handler to use less gas, or the sudo gas limit parameter must be increased through governance.

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Implementing Error Handling Patterns

Here’s a pattern for robust IBC acknowledgment handling: 
// Store received acknowledgment for later processing
#[entry_point]
pub fn sudo(deps: DepsMut, env: Env, msg: SudoMsg) -> Result<Response, ContractError> {
    match msg {
        SudoMsg::IbcAcknowledgement { ack, .. } => {
            // Just store the acknowledgment with minimal processing
            PENDING_ACKS.save(deps.storage, &ack)?;
            
            Ok(Response::new().add_attribute("action", "ack_stored"))
        },
        _ => Err(ContractError::UnknownSudoMsg {}),
    }
}

// Process stored acknowledgments with separate message
#[entry_point]
pub fn execute(deps: DepsMut, env: Env, info: MessageInfo, msg: ExecuteMsg) -> Result<Response, ContractError> {
    match msg {
        ExecuteMsg::ProcessPendingAcks {} => {
            let acks = PENDING_ACKS.load(deps.storage)?;
            // Process acks with full gas available
            // ...
            
            Ok(Response::new().add_attribute("action", "processed_acks"))
        },
        // Handle resubmission of failures
        ExecuteMsg::ResubmitFailure { id } => {
            Ok(Response::new()
                .add_message(NeutronMsg::ResubmitFailure { failure_id: id })
                .add_attribute("action", "resubmit"))
        },
        // Other execute messages
        // ...
    }
}

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Monitoring Contract Failures

For production applications, implement a monitoring system that:
  1. Regularly queries the Contract Manager for failures related to your contracts
  2. Alerts operators about new failures
  3. Provides tooling to diagnose and resubmit failures when appropriate
This can be implemented as a separate service that uses the Neutron RPC endpoints to monitor your contract’s status.

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Testing Contract Manager Integration

When testing contracts that interact with IBC:
  1. Test how your contract handles out-of-gas scenarios
  2. Verify that resubmission logic works correctly
  3. Ensure error states are properly captured and can be recovered from
You can use Neutron’s testnet environment to test these scenarios with actual IBC interactions.
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