Crank Counter

Automated execution with scheduled cranks in Ephemeral Rollups

Crank Counter

The Crank Counter example demonstrates how to use MagicBlock’s scheduled crank system to automatically execute instructions at specified intervals within Ephemeral Rollups. This advanced pattern enables autonomous program execution without manual intervention.

What Are Cranks?

Cranks are scheduled tasks that automatically execute specified instructions at regular intervals within an Ephemeral Rollup. This is particularly useful for:

• Automated game state updates
• Periodic reward distributions
• Scheduled maintenance operations
• Time-based game mechanics

Cranks execute entirely within the Ephemeral Rollup environment, providing low-latency automated execution without base layer transaction costs.

How It Works

Crank Parameters

Crank Arguments Structure

#[derive(AnchorSerialize, AnchorDeserialize)]
pub struct ScheduleIncrementArgs {
    pub task_id: u64,                      // Unique identifier for the crank task
    pub execution_interval_millis: u64,     // Time between executions in milliseconds
    pub iterations: u64,                    // Number of times to execute (0 = infinite)
}

Make sure your delegated account has sufficient commitment interval set to allow the crank to execute multiple times before automatic commits.

Program Setup

Your program must be annotated with the #[ephemeral] macro:

programs/crank-counter/src/lib.rs

use ephemeral_rollups_sdk::anchor::{commit, delegate, ephemeral};
use ephemeral_rollups_sdk::consts::MAGIC_PROGRAM_ID;
use magicblock_magic_program_api::{args::ScheduleTaskArgs, instruction::MagicBlockInstruction};

#[ephemeral]
#[program]
pub mod anchor_counter {
    use super::*;
    // ... your program code
}

Local Development

Use Cases

Cranks are particularly powerful for:

• Gaming: Auto-advance turn-based games, periodic resource regeneration
• DeFi: Scheduled interest calculations, automated liquidations
• NFTs: Time-based trait updates, dynamic metadata changes
• Social: Periodic content refresh, scheduled notifications

Next Steps

• Explore Magic Actions for executing base chain handlers on commit
• Learn about Session Keys for gasless transactions
• Check the full source code