chore(chain): add repo cache metrics

chain/cache.go

@@ -18,14 +18,17 @@ func newCache(maxSize int) *cache {
 	return &cache{c}
 }
 
-func (c *cache) GetOrLoad(key interface{}, load func() (interface{}, error)) (interface{}, error) {
+// GetOrLoad returns the value associated with the key if it exists in the cache.
+// Otherwise, it calls the load function to get the value and adds it to the cache.
+// It returns the value, a boolean indicating whether the value was cached, and an error if any.
+func (c *cache) GetOrLoad(key interface{}, load func() (interface{}, error)) (interface{}, bool, error) {
 	if value, ok := c.Get(key); ok {
-		return value, nil
+		return value, true, nil
 	}
 	value, err := load()
 	if err != nil {
-		return nil, err
+		return nil, false, err
 	}
 	c.Add(key, value)
-	return value, nil
+	return value, false, nil
 }

chain/metrics.go

@@ -0,0 +1,12 @@
+// Copyright (c) 2024 The VeChainThor developers
+//
+// Distributed under the GNU Lesser General Public License v3.0 software license, see the accompanying
+// file LICENSE or <https://www.gnu.org/licenses/lgpl-3.0.html>
+
+package chain
+
+import "github.com/vechain/thor/v2/metrics"
+
+var (
+	metricCacheHitMiss = metrics.LazyLoadCounterVec("repo_cache_hit_miss_count", []string{"type", "event"})
+)

chain/repository.go

@@ -284,22 +284,33 @@ func (r *Repository) GetMaxBlockNum() (uint32, error) {
 
 // GetBlockSummary get block summary by block id.
 func (r *Repository) GetBlockSummary(id thor.Bytes32) (summary *BlockSummary, err error) {
-	var cached interface{}
-	if cached, err = r.caches.summaries.GetOrLoad(id, func() (interface{}, error) {
+	var blk interface{}
+	var cached bool
+	if blk, cached, err = r.caches.summaries.GetOrLoad(id, func() (interface{}, error) {
 		return loadBlockSummary(r.hdrStore, id)
 	}); err != nil {
 		return
 	}
-	return cached.(*BlockSummary), nil
+	if cached {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "blocks", "event": "hit"})
+	} else {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "blocks", "event": "miss"})
+	}
+	return blk.(*BlockSummary), nil
 }
 
 func (r *Repository) getTransaction(key []byte) (*tx.Transaction, error) {
-	trx, err := r.caches.txs.GetOrLoad(string(key), func() (interface{}, error) {
+	trx, cached, err := r.caches.txs.GetOrLoad(string(key), func() (interface{}, error) {
 		return loadTransaction(r.bodyStore, key)
 	})
 	if err != nil {
 		return nil, err
 	}
+	if cached {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "transaction", "event": "hit"})
+	} else {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "transaction", "event": "miss"})
+	}
 	return trx.(*tx.Transaction), nil
 }
 
@@ -346,14 +357,20 @@ func (r *Repository) GetBlock(id thor.Bytes32) (*block.Block, error) {
 	return block.Compose(summary.Header, txs), nil
 }
 
+
 func (r *Repository) getReceipt(key []byte) (*tx.Receipt, error) {
-	cached, err := r.caches.receipts.GetOrLoad(string(key), func() (interface{}, error) {
+	receipt, cached, err := r.caches.receipts.GetOrLoad(string(key), func() (interface{}, error) {
 		return loadReceipt(r.bodyStore, key)
 	})
 	if err != nil {
 		return nil, err
 	}
-	return cached.(*tx.Receipt), nil
+	if cached {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "receipt", "event": "hit"})
+	} else {
+		metricCacheHitMiss().AddWithLabel(1, map[string]string{"type": "receipt", "event": "miss"})
+	}
+	return receipt.(*tx.Receipt), nil
 }
 
 func loadReceipt(r kv.Getter, key []byte) (*tx.Receipt, error) {