[AHM] Async Staking module across AH and RC (#8127)

Moved from: #7601.
Follow ups to: #7282.
Closes: #8146

---

This PR is the final outcome of a multi-month development period, with a
lot of background work
since 2022. Its main aim is to make pallet-staking, alongside its `type
ElectionProvider`
compatible to be used in a parachain, and report back the validator set
to a relay-chain.

This setup is intended to be used for Polkadot, Kusama and Westend
relay-chains, with the
corresponding AssetHubs hosting the staking system.

While this PR is quite big, a lot of the diffs are due to adding a relay
and parachain runtime
for testing. The following is a guide to help reviewers/auditors
distinguish what has actually
changed in this PR.

> Additional reading: See
polkadot-js/apps#11401, and the hackmd shared
in there, which contains more in-depth explanation of how RC <> AH
communicate.

## Added

> [This shows the partial
diff](ankn/diff-staking-async...ankn/diff-staking-async-1)
introduced in pallet-staking-async and election-provider-multi-block
relative to the existing (in master) pallet-staking and
election-provider-multi-phase.

This PR adds the following new pallets, all of which are not used
anywhere yet, with the
exception of one (see `westend-runtime` changes below).

#### `pallet-election-provider-multi-block`

This is a set of 4 pallets, capable of implementing an async, multi-page
`ElectionProvider`.
This pallet is not used in any real runtime yet, and is intended to be
used in `AssetHub`, next
to `pallet-staking-async`.

#### `pallet-staking-async`

A fork of the old `pallet-staking`, with a number of key differences,
making it suitable to be
used in a parachain:

1. It no longer has access to a secure timestamp, previously used to
calculate the duration of an era.
2. It no longer has access to a `pallet-session`. 
3. It no longer has access to a `pallet-authorship`. 
5. It is capable of working with a multi-page `ElectionProvider`, aka.
`pallet-election-provider-multi-block`.

To compensate for the above, this pallet relies on XCM messages coming
from the relay-chain,
informing the pallet of:

* When a new era should be activated, and how long its duration was
* When an offence has happened on the relay relay-chain
* When a session ends on the relay-chain, and how many reward points
were accumulated for each
validators during that period.

#### `pallet-staking-async-ah-client` and
`pallet-staking-async-rc-client`

Are the two new pallets that facilitate the above communication.

#### `pallet-ahm-test`

A test-only crate that contains e2e rust-based unit test for all of the
above.

#### `pallet-staking-async-rc-runtime` and
`pallet-staking-async-parachain-runtime`

Forks of westend and westend-asset-hub, customized to be used for
testing all of the above with
Zombienet. It contains a lot of unrelated code as well.

## Changed

> [This shows the partial
diff](ankn/8127-diff-changed-base...ankn/8127-diff-changed-compare)
that shows the changes to existing pallets used in prod runtimes as well
as westend runtime changes.

#### `Identification`

This mechanism, which lives on the relay-chain, is expressed by `type
FullIdentification` and `type FullIdentificationOf` in runtimes. It is a
way to identify the full data needed to slash a validator. Historically,
it was pointing to a validator, and their `struct Exposure`. With the
move to Asset-Hub, this is no longer possible for two reasons:

1. Relay chain no longer knows the full exposures
2. Even if, the full exposures are getting bigger and bigger and relying
the entirety of it is not scalable.

Instead, runtimes now move to a new `type FullIdentificationOf =
DefaultExposureOf`, which will identify a validator with a
`Exposure::default()`. This is suboptimal, as it forces us to still
store a number of bytes. Yet, it allows any old `FullIdentification`,
pertaining to an old slash, to be decoded. This compromise is only
needed to cater for slashes that happen around the time of AHM.

#### `westend-runtime`

This runtime already has the `pallet-staking-async-ah-client`,
integrated into all the places such that:

1. It handles the validator reward points
2. It handles offences
5. It is the `SessionManager`

Yet, it is delegating all of the above to its `type Fallback`, which is
the old `pallet-staking`. This is a preparatory step for AHM, and should
not be any logical change.

#### `pallet-election-provider-multi-phase`

This is the old single-page `ElectionProvider`. It has been updated to
work with multi-page traits, yet it only supports `page-size = 1` for
now. It should not have seen any logical changes.


#### `pallet-bags-list`

Now has two new features. 1. It can be `Locked`, in which case all
updates to it fail with an
`Err(_)`, even deletion of a node. This is needed because we cannot
alter any nodes in this
pallet during a multi-page iteration, aka. multi-page snapshot. 2. To
combat this, the same
`rebag` transaction can be also be used to remove a node from the list,
or add a node to the
list. This is done through the `score_of` api.

See the file changes and tests under `./substrate/frame/bags-list` for
more info.

#### RuntimeDebug -> Debug

To facilitate debugging, a number of types' `RuntimeDebug` impl has been
changed to `Debug`. See
#3107


## Weights 

Below is a summary of the weights. These are generated using
`staking-async/runtimes/parachain`, which assumes 22_500 nominators
divided by `32` pages for Polkadot, and 12_500 nominators divided by
`16` pages in Kusama, both leading to ~700 nominators snapshotted and
exported per page. Doubling these parameters would easily slash the PoV
weights by half, but with 10MB PoV, these numbers should be good. Also
noting that with PoV clawback, we migth get even more proof_size weight
back in the runtime. Although, afaik this reclaimed value does not take
compression into account.

```
#### new: polkadot/pallet_election_provider_multi_block.rs old: kusama
+-----------------------------------------+--------------------------------------+---------+---------+-----------------+
| File                                    | Extrinsic                            | Old     | New     | Change [%]      |
+======================================================================================================================+
| pallet_election_provider_multi_block.rs | on_initialize_into_snapshot_msp      | 2.41MiB | 2.41MiB | -0.03  |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | on_initialize_into_snapshot_rest     | 3.24MiB | 3.06MiB | -5.53  |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | on_initialize_into_signed            | 3.36MiB | 3.12MiB | -7.12  |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | export_non_terminal                  | 2.12MiB | 1.32MiB | -37.60 |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | export_terminal                      | 4.08MiB | 2.25MiB | -44.82 |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | on_initialize_nothing                | 3.53KiB | 3.53KiB | Unchanged       |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | on_initialize_into_unsigned          | 3.71KiB | 3.71KiB | Unchanged       |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | on_initialize_into_signed_validation | 3.71KiB | 3.71KiB | Unchanged       |
|-----------------------------------------+--------------------------------------+---------+---------+-----------------|
| pallet_election_provider_multi_block.rs | manage                               | 0B      | 0B      | Unchanged       |
+-----------------------------------------+--------------------------------------+---------+---------+-----------------+
#### new: polkadot/pallet_election_provider_multi_block_signed.rs old: kusama
+------------------------------------------------+----------------------+----------+----------+-----------------+
| File                                           | Extrinsic            | Old      | New      | Change [%]      |
+===============================================================================================================+
| pallet_election_provider_multi_block_signed.rs | bail                 | 43.61KiB | 82.74KiB | +89.72 |
|------------------------------------------------+----------------------+----------+----------+-----------------|
| pallet_election_provider_multi_block_signed.rs | register_eject       | 46.54KiB | 85.80KiB | +84.35 |
|------------------------------------------------+----------------------+----------+----------+-----------------|
| pallet_election_provider_multi_block_signed.rs | clear_old_round_data | 85.23KiB | 85.17KiB | -0.06  |
|------------------------------------------------+----------------------+----------+----------+-----------------|
| pallet_election_provider_multi_block_signed.rs | submit_page          | 6.95KiB  | 6.90KiB  | -0.70  |
|------------------------------------------------+----------------------+----------+----------+-----------------|
| pallet_election_provider_multi_block_signed.rs | register_not_full    | 6.45KiB  | 6.39KiB  | -1.00  |
|------------------------------------------------+----------------------+----------+----------+-----------------|
| pallet_election_provider_multi_block_signed.rs | unset_page           | 20.76KiB | 18.55KiB | -10.67 |
+------------------------------------------------+----------------------+----------+----------+-----------------+
#### new: polkadot/pallet_election_provider_multi_block_unsigned.rs old: kusama
+--------------------------------------------------+-------------------+----------+-----------+------------------+
| File                                             | Extrinsic         | Old      | New       | Change [%]       |
+================================================================================================================+
| pallet_election_provider_multi_block_unsigned.rs | submit_unsigned   | 63.56KiB | 696.00KiB | +995.01 |
|--------------------------------------------------+-------------------+----------+-----------+------------------|
| pallet_election_provider_multi_block_unsigned.rs | validate_unsigned | 1.81KiB  | 3.66KiB   | +102.65 |
+--------------------------------------------------+-------------------+----------+-----------+------------------+
#### new: polkadot/pallet_election_provider_multi_block_verifier.rs old: kusama
+--------------------------------------------------+------------------------------------+-----------+-----------+-----------------+
| File                                             | Extrinsic                          | Old       | New       | Change [%]      |
+=================================================================================================================================+
| pallet_election_provider_multi_block_verifier.rs | on_initialize_invalid_terminal     | 1.18MiB   | 1.69MiB   | +42.87 |
|--------------------------------------------------+------------------------------------+-----------+-----------+-----------------|
| pallet_election_provider_multi_block_verifier.rs | on_initialize_valid_terminal       | 1.18MiB   | 1.69MiB   | +42.71 |
|--------------------------------------------------+------------------------------------+-----------+-----------+-----------------|
| pallet_election_provider_multi_block_verifier.rs | on_initialize_invalid_non_terminal | 1.30MiB   | 450.82KiB | -66.08 |
|--------------------------------------------------+------------------------------------+-----------+-----------+-----------------|
| pallet_election_provider_multi_block_verifier.rs | on_initialize_valid_non_terminal   | 279.93KiB | 62.22KiB  | -77.77 |
+--------------------------------------------------+------------------------------------+-----------+-----------+-----------------+
```

<summary> 

note for PR authors

<details>

<br>

## TODO

- [x] Finalize weights
- [x] Lock voter list when snapshot being taken 
- [x] push based election
- [x] OffchainWorker miner can now run on multiple pages 
- [x] Trimming is improved, all bounds are respected.
- [x] clients pallets: add ID
- [x] make election prolonged
- [x] bring westend-next and ah-next to staking-next
- [x] Test pre-migration to post-migration state in ahm-test.
- [x] Offence reporting works without exposure info on RC (done but
recheck).
- [ ] staking-async fix tests
- [ ] root offence testing (minimally done in migration test)
- [ ] Run benchmarking
- [x] ~~Add custom decoder for OffenceDetails~~.

## TODO before finalizing PR
- [x] Go over again and ensure no interaction with staking-classic
except by AhClient (and pallets that are going away) in Westend. Make
any non used apis private.
- [ ] Create diff with changes from staking-classic.

## Migration Notes
- At the start of the AHM migration, trigger:
`RC::pallet_staking_async_ah_client::on_migration_start()`
- At the start of the AHM migration, trigger the following:
  - definitely filter `staking::bond`
  - RC: set `staking::Forcing` to `ForceNone`. 
- At the end of the AHM migration, trigger the following
  - `RC::pallet_staking_async_ah_client::on_migration_end()`
  - Set `AH::pallet_staking_async::ForceEra` to `Forcing::NotForcing`.
  - Set RC staking and pool min bond to be u32::max.

## Follow-up
- [ ] Offence generation e2e test (zombienet)

</details>
</summary>

---------

Co-authored-by: kianenigma <[email protected]>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Kian Paimani <[email protected]>
Co-authored-by: Tsvetomir Dimitrov <[email protected]>

Author: 4 people

Cargo.lock

@@ -352,6 +352,7 @@ members = [
 	"substrate/frame/core-fellowship",
 	"substrate/frame/delegated-staking",
 	"substrate/frame/democracy",
+	"substrate/frame/election-provider-multi-block",
 	"substrate/frame/election-provider-multi-phase",
 	"substrate/frame/election-provider-multi-phase/test-staking-e2e",
 	"substrate/frame/election-provider-support",
@@ -427,6 +428,15 @@ members = [
 	"substrate/frame/session/benchmarking",
 	"substrate/frame/society",
 	"substrate/frame/staking",
+	"substrate/frame/staking-async",
+	"substrate/frame/staking-async/ah-client",
+	"substrate/frame/staking-async/ahm-test",
+	"substrate/frame/staking-async/rc-client",
+	"substrate/frame/staking-async/reward-fn",
+	"substrate/frame/staking-async/runtime-api",
+	"substrate/frame/staking-async/runtimes/parachain",
+	"substrate/frame/staking-async/runtimes/rc",
+	"substrate/frame/staking-async/runtimes/rc/constants",
 	"substrate/frame/staking/reward-curve",
 	"substrate/frame/staking/reward-fn",
 	"substrate/frame/staking/runtime-api",
@@ -945,6 +955,7 @@ pallet-default-config-example = { path = "substrate/frame/examples/default-confi
 pallet-delegated-staking = { path = "substrate/frame/delegated-staking", default-features = false }
 pallet-democracy = { path = "substrate/frame/democracy", default-features = false }
 pallet-dev-mode = { path = "substrate/frame/examples/dev-mode", default-features = false }
+pallet-election-provider-multi-block = { path = "substrate/frame/election-provider-multi-block", default-features = false }
 pallet-election-provider-multi-phase = { path = "substrate/frame/election-provider-multi-phase", default-features = false }
 pallet-election-provider-support-benchmarking = { path = "substrate/frame/election-provider-support/benchmarking", default-features = false }
 pallet-elections-phragmen = { path = "substrate/frame/elections-phragmen", default-features = false }
@@ -1014,6 +1025,16 @@ pallet-staking = { path = "substrate/frame/staking", default-features = false }
 pallet-staking-reward-curve = { path = "substrate/frame/staking/reward-curve", default-features = false }
 pallet-staking-reward-fn = { path = "substrate/frame/staking/reward-fn", default-features = false }
 pallet-staking-runtime-api = { path = "substrate/frame/staking/runtime-api", default-features = false }
+# TODO: remove the reward stuff as they are not needed here
+pallet-staking-async = { path = "substrate/frame/staking-async", default-features = false }
+pallet-staking-async-ah-client = { path = "substrate/frame/staking-async/ah-client", default-features = false }
+pallet-staking-async-parachain-runtime = { path = "substrate/frame/staking-async/runtimes/parachain" }
+pallet-staking-async-rc-client = { path = "substrate/frame/staking-async/rc-client", default-features = false }
+pallet-staking-async-rc-runtime = { path = "substrate/frame/staking-async/runtimes/rc" }
+pallet-staking-async-rc-runtime-constants = { path = "substrate/frame/staking-async/runtimes/rc/constants", default-features = false }
+pallet-staking-async-reward-curve = { path = "substrate/frame/staking-async/reward-curve", default-features = false }
+pallet-staking-async-reward-fn = { path = "substrate/frame/staking-async/reward-fn", default-features = false }
+pallet-staking-async-runtime-api = { path = "substrate/frame/staking-async/runtime-api", default-features = false }
 pallet-state-trie-migration = { path = "substrate/frame/state-trie-migration", default-features = false }
 pallet-statement = { default-features = false, path = "substrate/frame/statement" }
 pallet-sudo = { path = "substrate/frame/sudo", default-features = false }

Cargo.toml

@@ -117,7 +117,6 @@ impl pallet_session::SessionHandler<u64> for TestSessionHandler {
 	}
 	fn on_new_session<Ks: OpaqueKeys>(_: bool, keys: &[(u64, Ks)], _: &[(u64, Ks)]) {
 		SessionChangeBlock::set(System::block_number());
-		dbg!(keys.len());
 		SessionHandlerCollators::set(keys.iter().map(|(a, _)| *a).collect::<Vec<_>>())
 	}
 	fn on_before_session_ending() {}

cumulus/pallets/collator-selection/src/mock.rs

@@ -335,7 +335,7 @@ mod tests {
 			.output()
 			.unwrap();
 
-		// atleast  blocks should be imported
+		// at least  blocks should be imported
 		assert!(String::from_utf8(output.stderr)
 			.unwrap()
 			.contains(format!("Imported #{}", 7).to_string().as_str()));

docs/sdk/src/guides/your_first_node.rs

@@ -73,7 +73,7 @@ const MERKLE_PROOF_MAX_DEPTH: usize = 8;
 
 /// The bomb limit for decompressing code blobs.
 #[deprecated(
-	note = "`VALIDATION_CODE_BOMB_LIMIT` will be removed. Use `validation_code_bomb_limit` 
+	note = "`VALIDATION_CODE_BOMB_LIMIT` will be removed. Use `validation_code_bomb_limit`
 	runtime API to retrieve the value from the runtime"
 )]
 pub const VALIDATION_CODE_BOMB_LIMIT: usize = (MAX_CODE_SIZE * 4u32) as usize;

polkadot/node/primitives/src/lib.rs

@@ -163,7 +163,7 @@ pub struct BlockData(#[cfg_attr(feature = "std", serde(with = "bytes"))] pub Vec
 	Ord,
 	PartialEq,
 	PartialOrd,
-	RuntimeDebug,
+	Debug,
 	serde::Serialize,
 	serde::Deserialize,
 	TypeInfo,

polkadot/parachain/src/primitives.rs

@@ -47,6 +47,9 @@ pallet-session = { workspace = true }
 pallet-staking = { workspace = true }
 pallet-timestamp = { workspace = true }
 
+# only used in benchmarking
+frame-election-provider-support = { workspace = true, optional = true }
+
 polkadot-primitives = { workspace = true }
 xcm = { workspace = true }
 xcm-executor = { workspace = true }
@@ -80,6 +83,7 @@ std = [
 	"bitvec/std",
 	"codec/std",
 	"frame-benchmarking?/std",
+	"frame-election-provider-support?/std",
 	"frame-support/std",
 	"frame-system/std",
 	"log/std",
@@ -118,6 +122,7 @@ std = [
 ]
 runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",
+	"frame-election-provider-support/runtime-benchmarks",
 	"frame-support-test/runtime-benchmarks",
 	"frame-support/runtime-benchmarks",
 	"frame-system/runtime-benchmarks",
@@ -139,6 +144,7 @@ runtime-benchmarks = [
 	"xcm/runtime-benchmarks",
 ]
 try-runtime = [
+	"frame-election-provider-support?/try-runtime",
 	"frame-support-test/try-runtime",
 	"frame-support/try-runtime",
 	"frame-system/try-runtime",

polkadot/runtime/parachains/Cargo.toml

@@ -82,6 +82,11 @@ where
 
 	pallet_session::Pallet::<T>::on_initialize(BlockNumberFor::<T>::one());
 	initializer::Pallet::<T>::on_initialize(BlockNumberFor::<T>::one());
+
+	// signal to `pallet-staking`'s `ElectionProvider` to be ready asap.
+	use frame_election_provider_support::ElectionProvider;
+	<<T as pallet_staking::Config>::ElectionProvider as ElectionProvider>::asap();
+
 	// skip sessions until the new validator set is enacted
 	while pallet_session::Pallet::<T>::validators().len() < n as usize {
 		pallet_session::Pallet::<T>::rotate_session();

polkadot/runtime/parachains/src/disputes/slashing/benchmarking.rs

@@ -59,7 +59,7 @@ pub mod pallet {
 		Encode,
 		Decode,
 		DecodeWithMemTracking,
-		sp_core::RuntimeDebug,
+		Debug,
 		scale_info::TypeInfo,
 		MaxEncodedLen,
 	)]

polkadot/runtime/parachains/src/origin.rs

@@ -23,7 +23,7 @@
 
 use crate::{session_info, shared};
 use alloc::collections::btree_set::BTreeSet;
-use frame_support::traits::{Defensive, ValidatorSet};
+use frame_support::traits::{Defensive, RewardsReporter, ValidatorSet};
 use polkadot_primitives::{SessionIndex, ValidatorIndex};
 
 /// The amount of era points given by backing a candidate that is included.
@@ -32,12 +32,13 @@ pub const BACKING_POINTS: u32 = 20;
 pub const DISPUTE_STATEMENT_POINTS: u32 = 20;
 
 /// Rewards validators for participating in parachains with era points in pallet-staking.
-pub struct RewardValidatorsWithEraPoints<C>(core::marker::PhantomData<C>);
+pub struct RewardValidatorsWithEraPoints<C, R>(core::marker::PhantomData<(C, R)>);
 
-impl<C> RewardValidatorsWithEraPoints<C>
+impl<C, R> RewardValidatorsWithEraPoints<C, R>
 where
-	C: pallet_staking::Config + session_info::Config,
+	C: session_info::Config,
 	C::ValidatorSet: ValidatorSet<C::AccountId, ValidatorId = C::AccountId>,
+	R: RewardsReporter<C::AccountId>,
 {
 	/// Reward validators in session with points, but only if they are in the active set.
 	fn reward_only_active(
@@ -61,14 +62,15 @@ where
 			.filter(|v| active_set.contains(v))
 			.map(|v| (v, points));
 
-		<pallet_staking::Pallet<C>>::reward_by_ids(rewards);
+		R::reward_by_ids(rewards);
 	}
 }
 
-impl<C> crate::inclusion::RewardValidators for RewardValidatorsWithEraPoints<C>
+impl<C, R> crate::inclusion::RewardValidators for RewardValidatorsWithEraPoints<C, R>
 where
-	C: pallet_staking::Config + shared::Config + session_info::Config,
+	C: shared::Config + session_info::Config,
 	C::ValidatorSet: ValidatorSet<C::AccountId, ValidatorId = C::AccountId>,
+	R: RewardsReporter<C::AccountId>,
 {
 	fn reward_backing(indices: impl IntoIterator<Item = ValidatorIndex>) {
 		let session_index = shared::CurrentSessionIndex::<C>::get();
@@ -78,10 +80,11 @@ where
 	fn reward_bitfields(_validators: impl IntoIterator<Item = ValidatorIndex>) {}
 }
 
-impl<C> crate::disputes::RewardValidators for RewardValidatorsWithEraPoints<C>
+impl<C, R> crate::disputes::RewardValidators for RewardValidatorsWithEraPoints<C, R>
 where
-	C: pallet_staking::Config + session_info::Config,
+	C: session_info::Config,
 	C::ValidatorSet: ValidatorSet<C::AccountId, ValidatorId = C::AccountId>,
+	R: RewardsReporter<C::AccountId>,
 {
 	fn reward_dispute_statement(
 		session: SessionIndex,