Timer

Verisense provides a powerful timer module that enables developers to schedule delayed or recurring function executions. The module consists of:

• #[init]
• #[timer]
• set_timer!()

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#[init]: Initialization Hook

A Rust function decorated with the #[init] attribute macro serves as a special initialization handler. This function is automatically invoked when a new version of the WASM module is deployed or upgraded.

Example:

#[init]
pub fn timer_init() {
    storage::put(b"delay", format!("init").as_bytes());
}

In this example, timer_init() will be called automatically upon deployment of a new AVS WASM version, allowing you to perform any necessary initialization tasks.

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set_timer! and #[timer]: Scheduling Timers

The set_timer! macro is used to schedule a new timer that triggers a handler function after a specified delay. Its syntax is:

set_timer!(Duration, timer_handler(params));

Basic Usage

#[post]
pub fn test_set_timer() {
    storage::put(b"delay", format!("init").as_bytes());

    let a = "abc".to_string();
    let b = 123;

    set_timer!(std::time::Duration::from_secs(4), test_delay(a, b));
}

#[timer]
pub fn test_delay(a: String, b: i32) {
    storage::put(b"delay", format!("delay_complete {} {}", a, b).as_bytes()).unwrap();
}

In this example:

• The test_set_timer function sets a timer that will trigger after 4 seconds.
• When the timer fires, the test_delay function is executed with the provided arguments.
• All timer handler functions must be decorated with the #[timer] attribute.

The set_timer! macro allows you to directly pass arguments to the timer handler, which are safely serialized and deserialized by the runtime.

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Implementing Intervals (Recurring Timers)

By default, set_timer! schedules one-shot timers. To implement periodic execution (intervals), you can schedule the next timer within the timer handler itself, effectively creating a recursive loop.

Example:

#[post]
pub fn test_set_timer() {
    set_timer!(std::time::Duration::from_secs(2), run_interval());
}

#[timer]
pub fn run_interval() {
    // Business logic executed on each interval
    storage::put(b"interval", b"running");

    // Schedule the next execution
    set_timer!(std::time::Duration::from_secs(1), run_interval());
}

In this pattern:

1. An initial timer is set to trigger after 2 seconds.
2. Inside run_interval, your business logic is executed.
3. At the end of each execution, a new timer is scheduled to run after 1 second.
4. This creates a continuous periodic execution loop.

This recursive approach allows you to implement interval-like behavior without native interval support.

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Summary

Component	Description
#[init]	Automatically called on WASM deployment or upgrade for initialization tasks.
set_timer!()	Schedules a one-shot timer to invoke a handler after a specified delay.
#[timer]	Marks a function as a valid timer handler callable by the runtime.
Intervals	Achieved by recursively scheduling timers within timer handlers.