AppChain Setup

After integrating the memlogger-enabled Cosmos SDK, you need to add streaming listeners to your chain’s application code. This enables real-time state change tracking.

Overview

The setup involves modifying your chain’s app.go file to:

1. Enable in-memory listeners on all KV stores
2. Attach the debug change logger to the streaming manager
3. Configure the streaming manager in your base app

Code Changes

Step 1: Add Required Imports

Add these imports to your app.go:

import (
    // ... your existing imports ...
 
    storetypes "cosmossdk.io/store/types"
    streamingabci "cosmossdk.io/store/streaming/abci"
)

Step 2: Add Streaming Listener Configuration

Find where your baseApp is initialized (typically after baseapp.NewBaseApp(...)), and add this code block immediately after:

// Always enable in-memory listeners on all KV stores so we can retrieve the
// per-block change set at commit time, regardless of external streaming config.
{
    var exposeStoreKeys []storetypes.StoreKey
    for _, k := range keys {
        exposeStoreKeys = append(exposeStoreKeys, k)
    }
    bApp.CommitMultiStore().AddListeners(exposeStoreKeys)
 
    // Append our in-process debug change logger to the streaming manager so it
    // receives the commit-time change set and logs a summary.
    sm := bApp.StreamingManager()
    sm.ABCIListeners = append(sm.ABCIListeners, &streamingabci.DebugChangeLogger{})
    bApp.SetStreamingManager(sm)
}

Complete Example

Here’s a complete example of the integration. The code should be placed right after your baseApp initialization:

// Create base app
bApp := baseapp.NewBaseApp(
    appName,
    logger,
    db,
    txConfig.TxDecoder(),
    baseAppOptions...,
)
 
// ========== ADD THIS BLOCK ==========
// Enable in-memory streaming listeners for state change tracking
{
    var exposeStoreKeys []storetypes.StoreKey
    for _, k := range keys {
        exposeStoreKeys = append(exposeStoreKeys, k)
    }
    bApp.CommitMultiStore().AddListeners(exposeStoreKeys)
 
    // Add debug change logger to streaming manager
    sm := bApp.StreamingManager()
    sm.ABCIListeners = append(sm.ABCIListeners, &streamingabci.DebugChangeLogger{})
    bApp.SetStreamingManager(sm)
}
// ====================================
 
// Continue with rest of app initialization...

Reference Implementation

For a complete working example, see the EVM chain integration:

• Repository: bft-labs/evm
• Release: v0.5.0-bft-labs-memlogger
• Commit: 9ba9acdfb37bd1d73b7e13b2534278a9fd60a0a1

This commit shows exactly how to set up app.go in a real-world chain.

Understanding the Code

Store Keys Collection

var exposeStoreKeys []storetypes.StoreKey
for _, k := range keys {
    exposeStoreKeys = append(exposeStoreKeys, k)
}

This collects all KV store keys from your application, ensuring every state change is tracked.

Adding Listeners

bApp.CommitMultiStore().AddListeners(exposeStoreKeys)

Registers listeners on all stores to capture state changes during block commits.

Debug Change Logger

sm.ABCIListeners = append(sm.ABCIListeners, &streamingabci.DebugChangeLogger{})

Adds the debug change logger that will output detailed state change information to the memlogger.

Verification

After making these changes, rebuild your chain:

# Build your chain
go build -o ./build/chaind ./cmd/chaind
 
# Verify the build succeeded
./build/chaind version

What Gets Tracked

With this setup enabled, the following information is captured for each block:

• Store changes: All KV store write operations
• Change sets: Complete diff of state changes per block
• Consensus events: Critical ABCI events
• Timing information: When changes occurred

Next Steps

Now that your application is configured, proceed to:

1. Node Configuration - Configure config.toml and app.toml settings

Troubleshooting

Build Errors

If you encounter build errors:

# Ensure dependencies are updated
go mod tidy
go mod vendor  # if using vendoring
 
# Clean build cache
go clean -cache

Missing Imports

If imports are not found:

• Verify you’re using the memlogger-enabled Cosmos SDK
• Check your go.mod replace directive
• Run go mod download

Runtime Errors

If you see runtime errors about streaming:

• Verify the code is placed AFTER baseApp initialization
• Ensure keys variable is defined and populated
• Check that you’re using the correct bApp variable name