Change distance evaluation period from Sessions to Blocks

Closes #202 (closed) Closes #207 (closed)

• Create evaluation period in block.
• Update tests.
• Weight accounting
• Upgrade the distance oracle.
• Fix #207 (closed).
• Closes #174 (closed): the worst and simplest estimation equates to one evaluation being 0.0037% of a block's weight, based on the current reference machine. To maintain a reasonable load on the system, it's advisable that the cumulative weight of all evaluations does not surpass 5-10% of a block's capacity. Consequently, setting MAX_EVALUATIONS_PER_SESSION between 1 300 and 2 600 would ensure safe operation.

pallets/distance/src/lib.rs

@@ -45,9 +45,9 @@ use sp_std::prelude::*;
 
 type IdtyIndex = u32;
 
-/// Maximum number of identities to be evaluated in a session
+/// Maximum number of identities to be evaluated in an evaluation period.
 pub const MAX_EVALUATIONS_PER_SESSION: u32 = 600;
-/// Maximum number of evaluators in a session
+/// Maximum number of evaluators in an evaluation period.
 pub const MAX_EVALUATORS_PER_SESSION: u32 = 100;
 
 #[frame_support::pallet()]
@@ -162,13 +162,6 @@ pub mod pallet {
     #[pallet::storage]
     pub(super) type CurrentPoolIndex<T: Config> = StorageValue<_, u32, ValueQuery>;
 
-    // session_index % 3:
-    //   storage_id + 0 => pending
-    //   storage_id + 1 => receives results
-    //   storage_id + 2 => receives new identities
-    // (this avoids problems for session_index < 3)
-    //
-
     #[pallet::event]
     #[pallet::generate_deposit(pub(super) fn deposit_event)]
     pub enum Event<T: Config> {
@@ -328,8 +321,8 @@ pub mod pallet {
 
     impl<T: Config> Pallet<T> {
         /// Mutate the evaluation pool containing:
-        /// * when this session begins: the evaluation results to be applied
-        /// * when this session ends: the evaluation requests
+        /// * when this period begins: the evaluation results to be applied.
+        /// * when this period ends: the evaluation requests.
         fn mutate_current_pool<
             R,
             F: FnOnce(
@@ -350,7 +343,7 @@ pub mod pallet {
             }
         }
 
-        /// Mutate the evaluation pool containing the results sent by evaluators on this session.
+        /// Mutate the evaluation pool containing the results sent by evaluators on this period.
         fn mutate_next_pool<
             R,
             F: FnOnce(
@@ -372,8 +365,8 @@ pub mod pallet {
         }
 
         /// Take (and leave empty) the evaluation pool containing:
-        /// * when this session begins: the evaluation results to be applied
-        /// * when this session ends: the evaluation requests
+        /// * when this period begins: the evaluation results to be applied.
+        /// * when this period ends: the evaluation requests.
         #[allow(clippy::type_complexity)]
         fn take_current_pool(
             index: u32,
@@ -527,8 +520,8 @@ pub mod pallet {
             // set evaluation block
             EvaluationBlock::<T>::set(frame_system::Pallet::<T>::parent_hash());
 
-            // Apply the results from the current pool (which was previous session's result pool)
-            // We take the results so the pool is left empty for the new session.
+            // Apply the results from the current pool (which was previous period's result pool)
+            // We take the results so the pool is left empty for the new period.
             #[allow(clippy::type_complexity)]
             let current_pool: EvaluationPool<
                 <T as frame_system::Config>::AccountId,