Fixup backing group computation time (#3170)

Fixes: https://github.com/paritytech/polkadot-sdk/issues/3165

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

.gitlab/pipeline/zombienet/polkadot.yml

@@ -150,6 +150,14 @@ zombienet-polkadot-functional-0010-validator-disabling:
       --local-dir="${LOCAL_DIR}/functional"
       --test="0010-validator-disabling.zndsl"
 
+zombienet-polkadot-functional-0011-async-backing-6-seconds-rate:
+  extends:
+    - .zombienet-polkadot-common
+  script:
+    - /home/nonroot/zombie-net/scripts/ci/run-test-local-env-manager.sh
+      --local-dir="${LOCAL_DIR}/functional"
+      --test="0011-async-backing-6-seconds-rate.zndsl"
+
 zombienet-polkadot-smoke-0001-parachains-smoke-test:
   extends:
     - .zombienet-polkadot-common

polkadot/runtime/parachains/src/runtime_api_impl/v7.rs

@@ -45,6 +45,8 @@ pub fn validators<T: initializer::Config>() -> Vec<ValidatorId> {
 /// Implementation for the `validator_groups` function of the runtime API.
 pub fn validator_groups<T: initializer::Config>(
 ) -> (Vec<Vec<ValidatorIndex>>, GroupRotationInfo<BlockNumberFor<T>>) {
+	// This formula needs to be the same as the one we use
+	// when populating group_responsible in `availability_cores`
 	let now = <frame_system::Pallet<T>>::block_number() + One::one();
 
 	let groups = <scheduler::Pallet<T>>::validator_groups();
@@ -95,6 +97,11 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::Hash, Bl
 						.expect("Occupied core always has pending availability; qed");
 
 				let backed_in_number = *pending_availability.backed_in_number();
+
+				// Use the same block number for determining the responsible group as what the
+				// backing subsystem would use when it calls validator_groups api.
+				let backing_group_allocation_time =
+					pending_availability.relay_parent_number() + One::one();
 				CoreState::Occupied(OccupiedCore {
 					next_up_on_available: <scheduler::Pallet<T>>::next_up_on_available(CoreIndex(
 						i as u32,
@@ -106,7 +113,7 @@ pub fn availability_cores<T: initializer::Config>() -> Vec<CoreState<T::Hash, Bl
 					)),
 					availability: pending_availability.availability_votes().clone(),
 					group_responsible: group_responsible_for(
-						backed_in_number,
+						backing_group_allocation_time,
 						pending_availability.core_occupied(),
 					),
 					candidate_hash: pending_availability.candidate_hash(),

polkadot/zombienet_tests/functional/0011-async-backing-6-seconds-rate.toml

@@ -0,0 +1,51 @@
+[settings]
+timeout = 1000
+
+[relaychain]
+default_image = "{{ZOMBIENET_INTEGRATION_TEST_IMAGE}}"
+chain = "rococo-local"
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config]
+  needed_approvals = 4
+  relay_vrf_modulo_samples = 6
+  scheduling_lookahead = 2
+  group_rotation_frequency = 4
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config.async_backing_params]
+  max_candidate_depth = 3
+  allowed_ancestry_len = 2
+
+[relaychain.default_resources]
+limits = { memory = "4G", cpu = "2" }
+requests = { memory = "2G", cpu = "1" }
+
+  [[relaychain.node_groups]]
+  name = "alice"
+  args = [ "-lparachain=debug" ]
+  count = 12
+
+[[parachains]]
+id = 2000
+addToGenesis = true
+genesis_state_generator = "undying-collator export-genesis-state --pov-size=100000 --pvf-complexity=1"
+
+  [parachains.collator]
+  name = "collator01"
+  image = "{{COL_IMAGE}}"
+  command = "undying-collator"
+  args = ["-lparachain=debug", "--pov-size=100000", "--pvf-complexity=1", "--parachain-id=2000"]
+
+[[parachains]]
+id = 2001
+cumulus_based = true
+
+  [parachains.collator]
+  name = "collator02"
+  image = "{{CUMULUS_IMAGE}}"
+  command = "polkadot-parachain"
+  args = ["-lparachain=debug"]
+
+[types.Header]
+number = "u64"
+parent_hash = "Hash"
+post_state = "Hash"

polkadot/zombienet_tests/functional/0011-async-backing-6-seconds-rate.zndsl

@@ -0,0 +1,20 @@
+Description: Test we are producing blocks at 6 seconds clip
+Network: ./0011-async-backing-6-seconds-rate.toml
+Creds: config
+
+# Check authority status.
+alice: reports node_roles is 4
+
+# Ensure parachains are registered.
+alice: parachain 2000 is registered within 60 seconds
+alice: parachain 2001 is registered within 60 seconds
+
+# Ensure parachains made progress.
+alice: reports substrate_block_height{status="finalized"} is at least 10 within 100 seconds
+
+# This parachains should produce blocks at 6s clip, let's assume an 8s rate, allowing for
+# some slots to be missed on slower machines
+alice: parachain 2000 block height is at least 30 within 240 seconds
+# This should already have produced the needed blocks
+alice: parachain 2001 block height is at least 30 within 6 seconds
+