header_map: impl Drop for HeaderMapKernel to persist header_map from memory to SledBackend

Signed-off-by: Eval EXEC <execvy@gmail.com>

Author: eval-exec

shared/src/types/header_map/backend_sled.rs

@@ -1,3 +1,5 @@
+#![allow(unused)]
+
 use crate::types::HeaderIndexView;
 use ckb_types::{packed::Byte32, prelude::*};
 use sled::{Config, Db, Mode};

shared/src/types/header_map/kernel_lru.rs

@@ -2,6 +2,7 @@ use std::path;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
 
+use ckb_logger::info;
 #[cfg(feature = "stats")]
 use ckb_logger::info;
 use ckb_metrics::HistogramTimer;
@@ -43,7 +44,17 @@ struct HeaderMapKernelStats {
 
 impl Drop for HeaderMapKernel {
     fn drop(&mut self) {
-        todo!("move all memory map to backend when drop");
+        loop {
+            let items = self.memory.front_items(1024);
+            if items.is_empty() {
+                break;
+            }
+
+            self.backend.insert_batch(&items);
+            self.memory
+                .remove_batch(items.iter().map(|item| item.hash()), false);
+        }
+        info!("HeaderMap persisted all items to backend");
     }
 }
 
@@ -169,7 +180,7 @@ impl HeaderMapKernel {
         let _trace_timer: Option<HistogramTimer> = ckb_metrics::handle()
             .map(|handle| handle.ckb_header_map_limit_memory_duration.start_timer());
 
-        if let Some(values) = self.memory.front_n(self.memory_limit) {
+        if let Some(values) = self.memory.excess_items(self.memory_limit) {
             tokio::task::block_in_place(|| {
                 self.backend.insert_batch(&values);
             });

shared/src/types/header_map/memory.rs

@@ -120,7 +120,16 @@ impl MemoryMap {
         })
     }
 
-    pub(crate) fn front_n(&self, size_limit: usize) -> Option<Vec<HeaderIndexView>> {
+    pub(crate) fn front_items(&self, count: usize) -> Vec<HeaderIndexView> {
+        let guard = self.0.read();
+        guard
+            .iter()
+            .take(count)
+            .map(|(key, value)| (key.clone(), value.clone()).into())
+            .collect()
+    }
+
+    pub(crate) fn excess_items(&self, size_limit: usize) -> Option<Vec<HeaderIndexView>> {
         let guard = self.0.read();
         let size = guard.len();
         if size > size_limit {