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// Copyright (C) Moondance Labs Ltd.
// This file is part of Tanssi.
// Tanssi is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Tanssi is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Tanssi. If not, see <http://www.gnu.org/licenses/>
#![cfg_attr(not(feature = "std"), no_std)]
use frame_system::offchain::CreateInherent;
use frame_system::offchain::CreateSignedTransaction;
use {
frame_system::{
self as system, ensure_none, ensure_root, offchain::SubmitTransaction,
pallet_prelude::BlockNumberFor,
},
sp_runtime::transaction_validity::{InvalidTransaction, TransactionValidity, ValidTransaction},
};
pub use pallet::*;
#[frame_support::pallet]
pub mod pallet {
use {super::*, frame_support::pallet_prelude::*, frame_system::pallet_prelude::*};
#[pallet::pallet]
pub struct Pallet<T>(_);
#[pallet::config]
pub trait Config:
CreateSignedTransaction<Call<Self>> + CreateInherent<Call<Self>> + frame_system::Config
{
/// The overarching event type.
type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
/// Number of blocks of cooldown after unsigned transaction is included.
///
/// This ensures that we only accept unsigned transactions once, every `UnsignedInterval`
/// blocks.
#[pallet::constant]
type UnsignedInterval: Get<BlockNumberFor<Self>>;
}
#[pallet::storage]
pub(super) type OffchainWorkerTestEnabled<T> = StorageValue<_, bool, ValueQuery>;
/// Defines the block when next unsigned transaction will be accepted.
/// To prevent spam of unsigned (and unpaid!) transactions on the network,
/// we only allow one transaction every `T::UnsignedInterval` blocks.
/// This storage entry defines when new transaction is going to be accepted.
pub(super) type NextUnsignedAt<T: Config> = StorageValue<_, BlockNumberFor<T>, ValueQuery>;
#[pallet::genesis_config]
pub struct GenesisConfig<T: Config> {
pub _phantom_data: PhantomData<T>,
#[pallet::genesis_build]
impl<T: Config> BuildGenesisConfig for GenesisConfig<T> {
fn build(&self) {
<OffchainWorkerTestEnabled<T>>::put(&false);
#[pallet::hooks]
impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
/// Offchain worker entry point.
/// By implementing `fn offchain_worker` you declare a new offchain worker.
/// This function will be called when the node is fully synced and a new best block is
/// successfully imported.
/// Note that it's not guaranteed for offchain workers to run on EVERY block, there might
/// be cases where some blocks are skipped, or for some the worker runs twice (re-orgs),
/// so the code should be able to handle that.
fn offchain_worker(block_number: BlockNumberFor<T>) {
log::info!("Entering off-chain worker.");
// The entry point of your code called by off-chain worker
let res = Self::send_raw_unsigned_transaction(block_number);
if let Err(e) = res {
log::error!("Error: {}", e);
#[pallet::call]
impl<T: Config> Pallet<T> {
/// Switches on or off the offchain worker
/// Only root (or specified authority account) should be able to switch
/// the off-chain worker on and off to avoid enabling it by default in production
#[pallet::call_index(0)]
#[pallet::weight(T::DbWeight::get().write)]
#[allow(clippy::useless_conversion)]
pub fn set_offchain_worker(
origin: OriginFor<T>,
is_testing_enabled: bool,
) -> DispatchResultWithPostInfo {
ensure_root(origin)?;
OffchainWorkerTestEnabled::<T>::put(is_testing_enabled);
Ok(().into())
/// Submits unsigned transaction that emits an event
/// Can be triggered only by an offchain worker
#[pallet::call_index(1)]
pub fn submit_event_unsigned(
_block_number: BlockNumberFor<T>,
// This ensures that the function can only be called via unsigned transaction.
ensure_none(origin)?;
ensure!(
OffchainWorkerTestEnabled::<T>::get(),
Error::<T>::OffchainWorkerNotEnabled,
);
// Increment the block number at which we expect next unsigned transaction.
let current_block = <frame_system::Pallet<T>>::block_number();
// Emits offchain event
Self::deposit_event(Event::SimpleOffchainEvent);
<NextUnsignedAt<T>>::put(current_block + T::UnsignedInterval::get());
/// Events for the pallet.
#[pallet::event]
#[pallet::generate_deposit(pub(super) fn deposit_event)]
pub enum Event<T: Config> {
/// Simple offchain event
SimpleOffchainEvent,
#[pallet::error]
pub enum Error<T> {
OffchainWorkerNotEnabled,
#[pallet::validate_unsigned]
impl<T: Config> ValidateUnsigned for Pallet<T> {
type Call = Call<T>;
/// Validate unsigned call to this module.
/// By default unsigned transactions are disallowed, but implementing the validator
/// here we make sure that some particular calls (the ones produced by offchain worker)
/// are being whitelisted and marked as valid.
fn validate_unsigned(_source: TransactionSource, call: &Self::Call) -> TransactionValidity {
if let Call::submit_event_unsigned { block_number } = call {
Self::validate_transaction_parameters(block_number)
} else {
InvalidTransaction::Call.into()
/// A helper function to sign payload and send an unsigned transaction
fn send_raw_unsigned_transaction(block_number: BlockNumberFor<T>) -> Result<(), &'static str> {
// Make sure offchain worker testing is enabled
let is_offchain_worker_enabled = OffchainWorkerTestEnabled::<T>::get();
if !is_offchain_worker_enabled {
return Err("Offchain worker is not enabled");
// Make sure transaction can be sent
let next_unsigned_at = NextUnsignedAt::<T>::get();
if next_unsigned_at > block_number {
return Err("Too early to send unsigned transaction");
let call = Call::submit_event_unsigned { block_number };
let xt = T::create_inherent(call.into());
SubmitTransaction::<T, Call<T>>::submit_transaction(xt)
.map_err(|()| "Unable to submit unsigned transaction.")?;
Ok(())
fn validate_transaction_parameters(block_number: &BlockNumberFor<T>) -> TransactionValidity {
return InvalidTransaction::Call.into();
// Now let's check if the transaction has any chance to succeed.
if &next_unsigned_at > block_number {
return InvalidTransaction::Stale.into();
// Let's make sure to reject transactions from the future.
let current_block = <system::Pallet<T>>::block_number();
if ¤t_block < block_number {
return InvalidTransaction::Future.into();
ValidTransaction::with_tag_prefix("ExampleOffchainWorker")
// We set base priority to 2**20 and hope it's included before any other
// transactions in the pool. Next we tweak the priority depending on how much
// it differs from the current average. (the more it differs the more priority it
// has).
.priority(2u64.pow(20))
// This transaction does not require anything else to go before into the pool.
// In theory we could require `previous_unsigned_at` transaction to go first,
// but it's not necessary in our case.
//.and_requires()
// We set the `provides` tag to be the same as `next_unsigned_at`. This makes
// sure only one transaction produced after `next_unsigned_at` will ever
// get to the transaction pool and will end up in the block.
// We can still have multiple transactions compete for the same "spot",
// and the one with higher priority will replace other one in the pool.
.and_provides(next_unsigned_at)
// The transaction is only valid for next 5 blocks. After that it's
// going to be revalidated by the pool.
.longevity(6)
// It's fine to propagate that transaction to other peers, which means it can be
// created even by nodes that don't produce blocks.
// Note that sometimes it's better to keep it for yourself (if you are the block
// producer), since for instance in some schemes others may copy your solution and
// claim a reward.
.propagate(true)
.build()