refactor: extract MAX_BLOCK_INTERVAL to constant

Author: rphmeier

sugondat/chain/node/src/proposer.rs

@@ -24,7 +24,10 @@ use cumulus_pallet_parachain_system::relay_state_snapshot::RelayChainStateProof;
 use cumulus_primitives_core::ParaId;
 use cumulus_primitives_parachain_inherent::ParachainInherentData;
 
-use sugondat_primitives::opaque::{Block, Header};
+use sugondat_primitives::{
+    opaque::{Block, Header},
+    MAX_SKIPPED_BLOCKS,
+};
 
 use std::sync::Arc;
 use std::time::Duration;
@@ -116,15 +119,6 @@ where
             };
             let relay_block_number = paras_inherent_data.validation_data.relay_parent_number;
 
-            // TODO: Change 3600 to 7200 (half a day)
-            // and `n_skipped_blocks = relay_parent_distance.saturating_sub(1)`
-            // when updating to asynchronous backing
-            // https://github.com/thrumdev/blobs/issues/166
-
-            // The accepted error is less than 10^(-2) for an expected
-            // maximum of 3600 skipped blocks (half a day)
-            const MAX_SKIPPED_BLOCKS: u32 = 3600;
-
             let relay_parent_distance = relay_block_number.saturating_sub(last_relay_block_number);
             let n_skipped_blocks = relay_parent_distance.saturating_sub(2) / 2;
             n_skipped_blocks >= MAX_SKIPPED_BLOCKS

sugondat/chain/primitives/src/lib.rs

@@ -8,6 +8,22 @@ use sp_runtime::{
 // Maximum Length of the Block in bytes
 pub const MAXIMUM_BLOCK_LENGTH: u32 = 5 * 1024 * 1024;
 
+/// The maximum acceptable number of skipped parachain blocks.
+///
+/// This is not a hard limit, but it should be respected by block proposers
+/// in order to ensure that the error in fee calculations does not exceed
+/// 10^(-2). Blob runtimes use an imperfect approximation of e^x when updating fee
+/// levels after long periods of inactivity. This approximation loses
+/// fidelity when many blocks are skipped.
+/// (https://github.com/thrumdev/blobs/issues/165)
+///
+/// The value of 3600 has been chosen as it is half a day's worth of blocks
+/// at a 12-second block interval.
+// TODO: Change 3600 to 7200 (half a day)
+// when updating to asynchronous backing
+// https://github.com/thrumdev/blobs/issues/166
+pub const MAX_SKIPPED_BLOCKS: BlockNumber = 3600;
+
 /// An index to a block.
 pub type BlockNumber = u32;