block-sdk/lanes/free

Free Lane

Leverage the free lane to encourage certain activity (such as staking) on your chain.

📖 Overview

The Free Lane is a lane that allows transactions to be included in the next block for free. By default, transactions that are staking related (e.g. delegation, undelegation, redelegate, etc.) are included in the Free Lane, however, this can be easily replaced! For more information on that, please see the MatchHandler section in the README found in block-sdk/block/base.

🏗️ Setup

Note

For a more in depth example of how to use the Block SDK, check out our example application in block-sdk/tests/app/app.go.

📦 Dependencies

The Block SDK is built on top of the Cosmos SDK. The Block SDK is currently compatible with Cosmos SDK versions greater than or equal to v0.47.0.

📥 Installation

To install the Block SDK, run the following command:

$ go get github.com/skip-mev/block-sdk/abci
$ go get github.com/skip-mev/block-sdk/lanes/free

📚 Usage

1. First determine the set of lanes that you want to use in your application. The available lanes can be found in our Lane App Store in block-sdk/lanes. In your base application, you will need to create a LanedMempool composed of the lanes that you want to use.
2. Next, order the lanes by priority. The first lane is the highest priority lane and the last lane is the lowest priority lane. Determine exactly where you want the free lane to be in the priority order.
3. Set up your FeeDeductorDecorator to ignore the free lane where ever you initialize your AnteHandler. This will ensure that the free lane is not subject to deducting transaction fees.
4. You will also need to create a PrepareProposalHandler and a ProcessProposalHandler that will be responsible for preparing and processing proposals respectively. Configure the order of the lanes in the PrepareProposalHandler and ProcessProposalHandler to match the order of the lanes in the LanedMempool.

import (
    "github.com/skip-mev/block-sdk/abci"
    "github.com/skip-mev/block-sdk/lanes/free"
)

...

func NewApp() {
    ...
    // 1. Create the lanes.
    //
    // NOTE: The lanes are ordered by priority. The first lane is the highest priority
    // lane and the last lane is the lowest priority lane. Top of block lane allows
    // transactions to bid for inclusion at the top of the next block.
    //
    // For more information on how to utilize the LaneConfig please
    // visit the README in block-sdk/block/base.
    //
    // MEV lane hosts an action at the top of the block.
    mevConfig := constructor.LaneConfig{
        Logger:        app.Logger(),
        TxEncoder:     app.txConfig.TxEncoder(),
        TxDecoder:     app.txConfig.TxDecoder(),
        MaxBlockSpace: math.LegacyZeroDec(), 
        MaxTxs:        0,
    }
    mevLane := mev.NewMEVLane(
        mevConfig,
        mev.NewDefaultAuctionFactory(app.txConfig.TxDecoder()),
    )

    // Free lane allows transactions to be included in the next block for free.
    freeConfig := constructor.LaneConfig{
        Logger:        app.Logger(),
        TxEncoder:     app.txConfig.TxEncoder(),
        TxDecoder:     app.txConfig.TxDecoder(),
        MaxBlockSpace: math.LegacyZeroDec(),
        MaxTxs:        0,
    }
    freeLane := free.NewFreeLane(
        freeConfig,
        constructor.DefaultTxPriority(),
        free.DefaultMatchHandler(),
    )

    // Default lane accepts all other transactions.
    defaultConfig := constructor.LaneConfig{
        Logger:        app.Logger(),
        TxEncoder:     app.txConfig.TxEncoder(),
        TxDecoder:     app.txConfig.TxDecoder(),
        MaxBlockSpace: math.LegacyZeroDec(),
        MaxTxs:        0,
    }
    defaultLane := base.NewStandardLane(defaultConfig)

    // 2. Set up the relateive priority of lanes
    lanes := []block.Lane{
        mevLane,
        freeLane,
        defaultLane,
    }
    mempool := block.NewLanedMempool(app.Logger(), true, lanes...)
    app.App.SetMempool(mempool)

    ...

    // 3. Set up the ante handler.
    anteDecorators := []sdk.AnteDecorator{
		ante.NewSetUpContextDecorator(),
        ...
		utils.NewIgnoreDecorator(
			ante.NewDeductFeeDecorator(
				options.BaseOptions.AccountKeeper,
				options.BaseOptions.BankKeeper,
				options.BaseOptions.FeegrantKeeper,
				options.BaseOptions.TxFeeChecker,
			),
			options.FreeLane,
		),
        ...
	}

    anteHandler := sdk.ChainAnteDecorators(anteDecorators...)

    // Set the lane ante handlers on the lanes.
    for _, lane := range lanes {
        lane.SetAnteHandler(anteHandler)
    }
    app.App.SetAnteHandler(anteHandler)

    // 4. Set the abci handlers on base app
    proposalHandler := abci.NewProposalHandler(
        app.Logger(),
        app.TxConfig().TxDecoder(),
        lanes,
    )
    app.App.SetPrepareProposal(proposalHandler.PrepareProposalHandler())
    app.App.SetProcessProposal(proposalHandler.ProcessProposalHandler())

    ...
}