feat: revisit caching strategy

Author: Ludo Galabru

components/chainhook-event-observer/src/hord/db/mod.rs

@@ -714,7 +714,7 @@ pub async fn fetch_and_cache_blocks_in_hord_db(
     let mut cursor = start_block as usize;
     let mut inbox = HashMap::new();
     let mut num_writes = 0;
-    let traversals_cache = Arc::new(new_traversals_lazy_cache());
+    let traversals_cache = Arc::new(new_traversals_lazy_cache(hord_config.cache_size));
 
     while let Ok(Some((block_height, compacted_block, raw_block))) = block_compressed_rx.recv() {
         insert_entry_in_blocks(block_height, &compacted_block, &blocks_db_rw, &ctx);
@@ -792,18 +792,20 @@ pub async fn fetch_and_cache_blocks_in_hord_db(
             return Ok(());
         }
 
-        if num_writes % 24 == 0 {
-            ctx.try_log(|logger| {
-                slog::info!(
-                    logger,
-                    "Flushing traversals cache (#{} entries)",
-                    traversals_cache.len()
-                );
-            });
-            traversals_cache.clear();
+        if !traversals_cache.is_empty() {
+            if num_writes % 128 == 0 {
+                ctx.try_log(|logger| {
+                    slog::info!(
+                        logger,
+                        "Flushing traversals cache (#{} entries)",
+                        traversals_cache.len()
+                    );
+                });
+                traversals_cache.shrink_to_fit();
+            }
         }
 
-        if num_writes % 128 == 0 {
+        if num_writes % 512 == 0 {
             ctx.try_log(|logger| {
                 slog::info!(logger, "Flushing DB to disk ({num_writes} inserts)");
             });

components/chainhook-event-observer/src/hord/mod.rs

@@ -18,6 +18,7 @@ use rocksdb::DB;
 use rusqlite::Connection;
 use std::collections::{BTreeMap, HashMap, VecDeque};
 use std::hash::BuildHasherDefault;
+use std::ops::Div;
 use std::path::PathBuf;
 use std::sync::mpsc::channel;
 use std::sync::Arc;
@@ -208,9 +209,14 @@ pub fn new_traversals_cache(
 }
 
 pub fn new_traversals_lazy_cache(
+    cache_size: usize,
 ) -> DashMap<(u32, [u8; 8]), LazyBlockTransaction, BuildHasherDefault<FxHasher>> {
     let hasher = FxBuildHasher::default();
-    DashMap::with_hasher(hasher)
+    DashMap::with_capacity_and_hasher(
+        ((cache_size.saturating_sub(500)) * 1000 * 1000)
+            .div(LazyBlockTransaction::get_average_bytes_size()),
+        hasher,
+    )
 }
 
 pub fn retrieve_inscribed_satoshi_points_from_block(