Expand description

Allows you to define some service work that can be recognized by a script or an off-chain worker.

Such a script can then create and submit all such work items at any given time.

These work items are defined as instances of the Task trait. pallet:tasks_experimental when attached to an impl block inside a pallet, will generate an enum Task<T> whose variants are mapped to functions inside this impl block.

Each such function must have the following set of attributes:

All of such Tasks are then aggregated into a RuntimeTask by construct_runtime.

Finally, the RuntimeTask can then used by a script or off-chain worker to create and submit such tasks via an extrinsic defined in frame_system called do_task.

When submitted as unsigned transactions (for example via an off-chain workder), note that the tasks will be executed in a random order.


impl<T: Config> Pallet<T> {
	/// Add a pair of numbers into the totals and remove them.
	#[pallet::task_condition(|i| Numbers::<T>::contains_key(i))]
	pub fn add_number_into_total(i: u32) -> DispatchResult {
		let v = Numbers::<T>::take(i).ok_or(Error::<T>::NotFound)?;
		Total::<T>::mutate(|(total_keys, total_values)| {
			*total_keys += i;
			*total_values += v;

Now, this can be executed as follows:

fn tasks_work() {
	new_test_ext().execute_with(|| {
		Numbers::<Runtime>::insert(0, 1);

		let task = RuntimeTask::System(super::frame_system::Task::<Runtime>::AddNumberIntoTotal {
			i: 0u32,

		assert_ok!(System::do_task(RuntimeOrigin::signed(1), task.clone(),));
		assert_eq!(Numbers::<Runtime>::get(0), None);
		assert_eq!(Total::<Runtime>::get(), (0, 1));

Rust-Analyzer users: See the documentation of the Rust item in frame_support::pallet_macros::tasks_experimental.