node: update flaming fir (#3508)

* node: reduce block time to 3s and add primary probability constant

* node: update flaming fir chain spec

* node: fix integration test

substrate/node/cli/src/service.rs

@@ -283,7 +283,7 @@ mod tests {
 	};
 	use node_primitives::DigestItem;
 	use node_runtime::{BalancesCall, Call, UncheckedExtrinsic};
-	use node_runtime::constants::{currency::CENTS, time::SLOT_DURATION};
+	use node_runtime::constants::{currency::CENTS, time::{PRIMARY_PROBABILITY, SLOT_DURATION}};
 	use codec::{Encode, Decode};
 	use primitives::{
 		crypto::Pair as CryptoPair, blake2_256,
@@ -404,7 +404,7 @@ mod tests {
 						slot_num,
 						&parent_header,
 						&*service.client(),
-						(278, 1000),
+						PRIMARY_PROBABILITY,
 						&keystore,
 					) {
 						break babe_pre_digest;

substrate/node/runtime/src/constants.rs

@@ -40,11 +40,19 @@ pub mod time {
 	/// that are expressed in blocks. The rest of the code should use
 	/// `SLOT_DURATION` instead (like the timestamp module for calculating the
 	/// minimum period).
+	///
+	/// If using BABE with secondary slots (default) then all of the slots will
+	/// always be assigned, in which case `MILLISECS_PER_BLOCK` and
+	/// `SLOT_DURATION` should have the same value.
+	///
 	/// <https://research.web3.foundation/en/latest/polkadot/BABE/Babe/#6-practical-results>
-	pub const MILLISECS_PER_BLOCK: Moment = 6000;
+	pub const MILLISECS_PER_BLOCK: Moment = 3000;
 	pub const SECS_PER_BLOCK: Moment = MILLISECS_PER_BLOCK / 1000;
 
-	pub const SLOT_DURATION: Moment = 6000;
+	pub const SLOT_DURATION: Moment = MILLISECS_PER_BLOCK;
+
+	// 1 in 4 blocks (on average, not counting collisions) will be primary BABE blocks.
+	pub const PRIMARY_PROBABILITY: (u64, u64) = (1, 4);
 
 	pub const EPOCH_DURATION_IN_BLOCKS: BlockNumber = 10 * MINUTES;
 	pub const EPOCH_DURATION_IN_SLOTS: u64 = {

substrate/node/runtime/src/lib.rs

@@ -563,7 +563,7 @@ impl_runtime_apis! {
 			babe_primitives::BabeConfiguration {
 				median_required_blocks: 1000,
 				slot_duration: Babe::slot_duration(),
-				c: (278, 1000),
+				c: PRIMARY_PROBABILITY,
 			}
 		}