Single Sequencer

Integrating single.Sequencer into Your System

This guide walks you through integrating the single.Sequencer from Rollkit into your custom system application. The process is modeled after the testapp example, focusing on the main steps and required components.

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1. Import Required Packages

In your main application (e.g., your cmd/run.go), import the following:

import (
    "context"
    "fmt"
    "path/filepath"

    "cosmossdk.io/log"
    "github.com/rollkit/rollkit/da/jsonrpc"
    "github.com/rollkit/rollkit/pkg/cmd"
    "github.com/rollkit/rollkit/pkg/config"
    "github.com/rollkit/rollkit/pkg/p2p"
    "github.com/rollkit/rollkit/pkg/p2p/key"
    "github.com/rollkit/rollkit/pkg/store"
    "github.com/rollkit/rollkit/sequencers/single"
    // ...other imports as needed
)

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2. Set Up Configuration and Logger

Parse your node configuration and set up logging:

nodeConfig, err := rollcmd.ParseConfig(cmd)
if err != nil {
    return err
}
logger := rollcmd.SetupLogger(nodeConfig.Log)

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3. Initialize the Data Availability (DA) Layer

Create a JSON-RPC DA client:

ctx, cancel := context.WithCancel(context.Background())
defer cancel()

daJrpc, err := jsonrpc.NewClient(ctx, logger, nodeConfig.DA.Address, nodeConfig.DA.AuthToken, nodeConfig.DA.Namespace)
if err != nil {
    return err
}

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4. Set Up the Datastore

Create a persistent key-value store for your system:

datastore, err := store.NewDefaultKVStore(nodeConfig.RootDir, nodeConfig.DBPath, "yourapp")
if err != nil {
    return err
}

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5. Initialize Sequencer Metrics (Optional)

If you want metrics, set them up (or use NopMetrics for no-op):

singleMetrics, err := single.NopMetrics()
if err != nil {
    return err
}

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6. Create the Single Sequencer

Instantiate the sequencer with the required parameters:

sequencer, err := single.NewSequencer(
    ctx,
    logger,
    datastore,
    &daJrpc.DA, // Pass the DA client
    []byte(nodeConfig.ChainID), // System ID
    nodeConfig.Node.BlockTime.Duration, // Batch time
    singleMetrics,
    nodeConfig.Node.Aggregator, // Proposer flag
)
if err != nil {
    return err
}

---

7. Set Up P2P Networking (Optional, but recommended)

If your system uses P2P, initialize the client:

nodeKey, err := key.LoadNodeKey(filepath.Dir(nodeConfig.ConfigPath()))
if err != nil {
    return err
}

p2pClient, err := p2p.NewClient(nodeConfig, nodeKey, datastore, logger, p2p.NopMetrics())
if err != nil {
    return err
}

---

8. Start Your Node

Finally, start your node with all the components:

return rollcmd.StartNode(
    logger,
    cmd,
    executor,    // Your application executor
    sequencer,   // The single sequencer
    &daJrpc.DA,  // DA client
    nodeKey,
    p2pClient,
    datastore,
    nodeConfig,
)

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9. (Optional) Start Any Application-Specific Services

For example, if you have an HTTP server for your executor, start it before the main node loop.

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Summary of Required Components

• Logger: For structured logging.
• Config: Node and application configuration.
• DA Client: JSON-RPC client for Data Availability.
• Datastore: Persistent storage for batches and state.
• Sequencer: The single.Sequencer instance.
• P2P Client: For networking (if needed).
• Executor: Your system’s application logic.

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Tips

• The single.Sequencer expects a batch submission channel to be set if you use batch submission loops.
• The DA client must implement the coreda.DA interface.
• The System ID should be unique for your chain.
• The batch time controls how frequently batches are produced.

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For a full working example, see the [testapp]https://github.com/rollkit/rollkit/blob/main/rollups/testapp/cmd/run.go in the Rollkit repo. Adapt the above steps to your own application’s needs.