contracts: Reduce session length and enable unstable interfaces (#1748)

* Reduce session for contracts to 10 minutes

* Build pallet-contracts with unstable interface

* Set `MinCandidates` to 0 to allow only invulnerables as collators

cumulus/parachains/runtimes/contracts/contracts-rococo/Cargo.toml

@@ -47,7 +47,7 @@ pallet-transaction-payment = { git = "https://github.com/paritytech/substrate",
 pallet-transaction-payment-rpc-runtime-api = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 pallet-utility = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 pallet-sudo = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
-pallet-contracts = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
+pallet-contracts = { git = "https://github.com/paritytech/substrate", default-features = false, features = ["unstable-interface"], branch = "master" }
 pallet-contracts-primitives = { git = "https://github.com/paritytech/substrate", default-features = false, branch = "master" }
 
 # Polkadot
@@ -131,12 +131,6 @@ std = [
 	"cumulus-primitives-utility/std",
 ]
 
-# Make contract callable functions marked as __unstable__ available. Do not enable
-# on live chains as those are subject to change.
-contracts-unstable-interface = [
-	"pallet-contracts/unstable-interface"
-]
-
 runtime-benchmarks = [
 	"hex-literal",
 	"frame-benchmarking/runtime-benchmarks",

cumulus/parachains/runtimes/contracts/contracts-rococo/src/lib.rs

@@ -58,7 +58,8 @@ use frame_system::limits::{BlockLength, BlockWeights};
 pub use parachains_common as common;
 use parachains_common::{
 	impls::DealWithFees, opaque, AccountId, BlockNumber, Hash, Header, Index, Signature,
-	AVERAGE_ON_INITIALIZE_RATIO, HOURS, MAXIMUM_BLOCK_WEIGHT, NORMAL_DISPATCH_RATIO, SLOT_DURATION,
+	AVERAGE_ON_INITIALIZE_RATIO, MAXIMUM_BLOCK_WEIGHT, MINUTES, NORMAL_DISPATCH_RATIO,
+	SLOT_DURATION,
 };
 pub use parachains_common::{AuraId, Balance};
 use xcm_config::CollatorSelectionUpdateOrigin;
@@ -269,7 +270,7 @@ impl parachain_info::Config for Runtime {}
 impl cumulus_pallet_aura_ext::Config for Runtime {}
 
 parameter_types! {
-	pub const Period: u32 = 6 * HOURS;
+	pub const Period: u32 = 10 * MINUTES;
 	pub const Offset: u32 = 0;
 }
 
@@ -303,7 +304,7 @@ impl pallet_collator_selection::Config for Runtime {
 	type UpdateOrigin = CollatorSelectionUpdateOrigin;
 	type PotId = PotId;
 	type MaxCandidates = ConstU32<1000>;
-	type MinCandidates = ConstU32<5>;
+	type MinCandidates = ConstU32<0>;
 	type MaxInvulnerables = ConstU32<100>;
 	// should be a multiple of session or things will get inconsistent
 	type KickThreshold = Period;