Make the historical bucket data private to `bucketed_history`

In a comming commit we'll cache some additional data in the
historical bucket tracker. In order to do so, here we isolate the
buckets themselves into the `bucketed_history` module, reducing
the possibility of accidentally updating them directly without
updating caches.

diff --git a/lightning/src/routing/scoring.rs b/lightning/src/routing/scoring.rs
index e979dbd7f595b57f4a783aa626ca2aecc588c5db..494a7db158edcbc814a73e73cb1424a4f0f36157 100644 (file)
--- a/lightning/src/routing/scoring.rs
+++ b/lightning/src/routing/scoring.rs
@@ -841,8 +841,8 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ProbabilisticScorer<G, L> whe
                                                let amt = directed_info.effective_capacity().as_msat();
                                                let dir_liq = liq.as_directed(source, target, amt);
 
-                                               let min_buckets = &dir_liq.liquidity_history.min_liquidity_offset_history.buckets;
-                                               let max_buckets = &dir_liq.liquidity_history.max_liquidity_offset_history.buckets;
+                                               let min_buckets = &dir_liq.liquidity_history.min_liquidity_offset_history_buckets();
+                                               let max_buckets = &dir_liq.liquidity_history.max_liquidity_offset_history_buckets();
 
                                                log_debug!(self.logger, core::concat!(
                                                        "Liquidity from {} to {} via {} is in the range ({}, {}).\n",
@@ -935,8 +935,8 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ProbabilisticScorer<G, L> whe
                                        let amt = directed_info.effective_capacity().as_msat();
                                        let dir_liq = liq.as_directed(source, target, amt);
 
-                                       let min_buckets = dir_liq.liquidity_history.min_liquidity_offset_history.buckets;
-                                       let mut max_buckets = dir_liq.liquidity_history.max_liquidity_offset_history.buckets;
+                                       let min_buckets = *dir_liq.liquidity_history.min_liquidity_offset_history_buckets();
+                                       let mut max_buckets = *dir_liq.liquidity_history.max_liquidity_offset_history_buckets();
 
                                        // Note that the liquidity buckets are an offset from the edge, so we inverse
                                        // the max order to get the probabilities from zero.
@@ -1281,11 +1281,10 @@ DirectedChannelLiquidity<L, BRT, T> {
        /// state"), we allow the caller to set an offset applied to our liquidity bounds which
        /// represents the amount of the successful payment we just made.
        fn update_history_buckets(&mut self, bucket_offset_msat: u64, duration_since_epoch: Duration) {
-               self.liquidity_history.min_liquidity_offset_history.track_datapoint(
-                       *self.min_liquidity_offset_msat + bucket_offset_msat, self.capacity_msat
-               );
-               self.liquidity_history.max_liquidity_offset_history.track_datapoint(
-                       self.max_liquidity_offset_msat.saturating_sub(bucket_offset_msat), self.capacity_msat
+               self.liquidity_history.track_datapoint(
+                       *self.min_liquidity_offset_msat + bucket_offset_msat,
+                       self.max_liquidity_offset_msat.saturating_sub(bucket_offset_msat),
+                       self.capacity_msat,
                );
                *self.offset_history_last_updated = duration_since_epoch;
        }
@@ -1451,19 +1450,12 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ScoreUpdate for Probabilistic
                        if elapsed_time > decay_params.historical_no_updates_half_life {
                                let half_life = decay_params.historical_no_updates_half_life.as_secs_f64();
                                if half_life != 0.0 {
-                                       let divisor = powf64(2048.0, elapsed_time.as_secs_f64() / half_life) as u64;
-                                       for bucket in liquidity.liquidity_history.min_liquidity_offset_history.buckets.iter_mut() {
-                                               *bucket = ((*bucket as u64) * 1024 / divisor) as u16;
-                                       }
-                                       for bucket in liquidity.liquidity_history.max_liquidity_offset_history.buckets.iter_mut() {
-                                               *bucket = ((*bucket as u64) * 1024 / divisor) as u16;
-                                       }
+                                       liquidity.liquidity_history.decay_buckets(elapsed_time.as_secs_f64() / half_life);
                                        liquidity.offset_history_last_updated = duration_since_epoch;
                                }
                        }
                        liquidity.min_liquidity_offset_msat != 0 || liquidity.max_liquidity_offset_msat != 0 ||
-                               liquidity.liquidity_history.min_liquidity_offset_history.buckets != [0; 32] ||
-                               liquidity.liquidity_history.max_liquidity_offset_history.buckets != [0; 32]
+                               liquidity.liquidity_history.has_datapoints()
                });
        }
 }
@@ -1593,7 +1585,7 @@ mod bucketed_history {
        /// in each of 32 buckets.
        #[derive(Clone, Copy)]
        pub(super) struct HistoricalBucketRangeTracker {
-               pub(super) buckets: [u16; 32],
+               buckets: [u16; 32],
        }
 
        /// Buckets are stored in fixed point numbers with a 5 bit fractional part. Thus, the value
@@ -1602,7 +1594,7 @@ mod bucketed_history {
 
        impl HistoricalBucketRangeTracker {
                pub(super) fn new() -> Self { Self { buckets: [0; 32] } }
-               pub(super) fn track_datapoint(&mut self, liquidity_offset_msat: u64, capacity_msat: u64) {
+               fn track_datapoint(&mut self, liquidity_offset_msat: u64, capacity_msat: u64) {
                        // We have 32 leaky buckets for min and max liquidity. Each bucket tracks the amount of time
                        // we spend in each bucket as a 16-bit fixed-point number with a 5 bit fractional part.
                        //
@@ -1638,11 +1630,10 @@ mod bucketed_history {
        impl_writeable_tlv_based!(HistoricalBucketRangeTracker, { (0, buckets, required) });
        impl_writeable_tlv_based!(LegacyHistoricalBucketRangeTracker, { (0, buckets, required) });
 
-
        #[derive(Clone, Copy)]
        pub(super) struct HistoricalLiquidityTracker {
-               pub(super) min_liquidity_offset_history: HistoricalBucketRangeTracker,
-               pub(super) max_liquidity_offset_history: HistoricalBucketRangeTracker,
+               min_liquidity_offset_history: HistoricalBucketRangeTracker,
+               max_liquidity_offset_history: HistoricalBucketRangeTracker,
        }
 
        impl HistoricalLiquidityTracker {
@@ -1663,6 +1654,29 @@ mod bucketed_history {
                        }
                }
 
+               pub(super) fn has_datapoints(&self) -> bool {
+                       self.min_liquidity_offset_history.buckets != [0; 32] ||
+                               self.max_liquidity_offset_history.buckets != [0; 32]
+               }
+
+               pub(super) fn decay_buckets(&mut self, half_lives: f64) {
+                       let divisor = powf64(2048.0, half_lives) as u64;
+                       for bucket in self.min_liquidity_offset_history.buckets.iter_mut() {
+                               *bucket = ((*bucket as u64) * 1024 / divisor) as u16;
+                       }
+                       for bucket in self.max_liquidity_offset_history.buckets.iter_mut() {
+                               *bucket = ((*bucket as u64) * 1024 / divisor) as u16;
+                       }
+               }
+
+               pub(super) fn writeable_min_offset_history(&self) -> &HistoricalBucketRangeTracker {
+                       &self.min_liquidity_offset_history
+               }
+
+               pub(super) fn writeable_max_offset_history(&self) -> &HistoricalBucketRangeTracker {
+                       &self.max_liquidity_offset_history
+               }
+
                pub(super) fn as_directed<'a>(&'a self, source_less_than_target: bool)
                -> HistoricalMinMaxBuckets<&'a HistoricalBucketRangeTracker> {
                        let (min_liquidity_offset_history, max_liquidity_offset_history) =
@@ -1691,13 +1705,30 @@ mod bucketed_history {
        pub(super) struct HistoricalMinMaxBuckets<D: Deref<Target = HistoricalBucketRangeTracker>> {
                /// Buckets tracking where and how often we've seen the minimum liquidity bound for a
                /// channel.
-               pub(super) min_liquidity_offset_history: D,
+               min_liquidity_offset_history: D,
                /// Buckets tracking where and how often we've seen the maximum liquidity bound for a
                /// channel.
-               pub(super) max_liquidity_offset_history: D,
+               max_liquidity_offset_history: D,
+       }
+
+       impl<D: DerefMut<Target = HistoricalBucketRangeTracker>> HistoricalMinMaxBuckets<D> {
+               pub(super) fn track_datapoint(
+                       &mut self, min_offset_msat: u64, max_offset_msat: u64, capacity_msat: u64,
+               ) {
+                       self.min_liquidity_offset_history.track_datapoint(min_offset_msat, capacity_msat);
+                       self.max_liquidity_offset_history.track_datapoint(max_offset_msat, capacity_msat);
+               }
        }
 
        impl<D: Deref<Target = HistoricalBucketRangeTracker>> HistoricalMinMaxBuckets<D> {
+               pub(super) fn min_liquidity_offset_history_buckets(&self) -> &[u16; 32] {
+                       &self.min_liquidity_offset_history.buckets
+               }
+
+               pub(super) fn max_liquidity_offset_history_buckets(&self) -> &[u16; 32] {
+                       &self.max_liquidity_offset_history.buckets
+               }
+
                #[inline]
                pub(super) fn calculate_success_probability_times_billion(
                        &self, params: &ProbabilisticScoringFeeParameters, amount_msat: u64,
@@ -1824,8 +1855,8 @@ impl Writeable for ChannelLiquidity {
                        (2, self.max_liquidity_offset_msat, required),
                        // 3 was the max_liquidity_offset_history in octile form
                        (4, self.last_updated, required),
-                       (5, self.liquidity_history.min_liquidity_offset_history, required),
-                       (7, self.liquidity_history.max_liquidity_offset_history, required),
+                       (5, self.liquidity_history.writeable_min_offset_history(), required),
+                       (7, self.liquidity_history.writeable_max_offset_history(), required),
                        (9, self.offset_history_last_updated, required),
                });
                Ok(())