From ca1444eb5d68c0a1c7f9d824d10dd5f245d2dd92 Mon Sep 17 00:00:00 2001
From: Jack Robison <jackrobison@lbry.io>
Date: Tue, 12 Apr 2022 15:27:28 -0400
Subject: [PATCH] cache cache histories from the db for mempool updates

---
 scribe/blockchain/service.py | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/scribe/blockchain/service.py b/scribe/blockchain/service.py
index b539ff0..1204213 100644
--- a/scribe/blockchain/service.py
+++ b/scribe/blockchain/service.py
@@ -11,7 +11,7 @@ from scribe import PROMETHEUS_NAMESPACE
 from scribe.db.prefixes import ACTIVATED_SUPPORT_TXO_TYPE, ACTIVATED_CLAIM_TXO_TYPE
 from scribe.db.prefixes import PendingActivationKey, PendingActivationValue, ClaimToTXOValue
 from scribe.error.base import ChainError
-from scribe.common import hash_to_hex_str, hash160, RPCError, HISTOGRAM_BUCKETS, StagedClaimtrieItem, sha256
+from scribe.common import hash_to_hex_str, hash160, RPCError, HISTOGRAM_BUCKETS, StagedClaimtrieItem, sha256, LRUCache
 from scribe.blockchain.daemon import LBCDaemon
 from scribe.blockchain.transaction import Tx, TxOutput, TxInput, Block
 from scribe.blockchain.prefetcher import Prefetcher
@@ -125,6 +125,9 @@ class BlockchainProcessorService(BlockchainService):
         self.pending_transaction_num_mapping: Dict[bytes, int] = {}
         self.pending_transactions: Dict[int, bytes] = {}
 
+        self.hashX_history_cache = LRUCache(100)
+        self.hashX_full_cache = LRUCache(100)
+
     async def run_in_thread_with_lock(self, func, *args):
         # Run in a thread to prevent blocking.  Shielded so that
         # cancellations from shutdown don't lose work - when the task
@@ -1244,14 +1247,30 @@ class BlockchainProcessorService(BlockchainService):
         self.touched_claims_to_send_es.difference_update(self.removed_claim_hashes)
         self.removed_claims_to_send_es.update(self.removed_claim_hashes)
 
+    def _get_cached_hashX_history(self, hashX: bytes) -> str:
+        if hashX in self.hashX_full_cache:
+            return self.hashX_full_cache[hashX]
+        if hashX not in self.hashX_history_cache:
+            self.hashX_history_cache[hashX] = tx_nums = self.db.read_history(hashX, limit=None)
+        else:
+            tx_nums = self.hashX_history_cache[hashX]
+        history = ''
+        for tx_num in tx_nums:
+            history += f'{hash_to_hex_str(self.db.get_tx_hash(tx_num))}:{bisect_right(self.db.tx_counts, tx_num):d}:'
+        self.hashX_full_cache[hashX] = history
+        return history
+
     def _get_update_hashX_status_ops(self, hashX: bytes, new_history: List[Tuple[bytes, int]]):
         existing = self.db.prefix_db.hashX_status.get(hashX)
         if existing:
             self.db.prefix_db.hashX_status.stage_delete((hashX,), existing)
-        tx_nums = self.db.read_history(hashX, limit=None)
+        if hashX not in self.hashX_history_cache:
+            tx_nums = self.db.read_history(hashX, limit=None)
+        else:
+            tx_nums = self.hashX_history_cache[hashX]
         history = ''
         for tx_num in tx_nums:
-            history += f'{hash_to_hex_str(self.db.get_tx_hash(tx_num) )}:{bisect_right(self.db.tx_counts, tx_num):d}:'
+            history += f'{hash_to_hex_str(self.db.get_tx_hash(tx_num))}:{bisect_right(self.db.tx_counts, tx_num):d}:'
         for tx_hash, height in new_history:
             history += f'{hash_to_hex_str(tx_hash)}:{height:d}:'
         if history:
@@ -1262,11 +1281,7 @@ class BlockchainProcessorService(BlockchainService):
         existing = self.db.prefix_db.hashX_mempool_status.get(hashX)
         if existing:
             self.db.prefix_db.hashX_mempool_status.stage_delete((hashX,), existing)
-        tx_nums = self.db.read_history(hashX, limit=None)
-        history = ''
-        for tx_num in tx_nums:
-            history += f'{hash_to_hex_str(self.db.get_tx_hash(tx_num) )}:{bisect_right(self.db.tx_counts, tx_num):d}:'
-        history += self.mempool.mempool_history(hashX)
+        history = self._get_cached_hashX_history(hashX) + self.mempool.mempool_history(hashX)
         if history:
             status = sha256(history.encode())
             self.db.prefix_db.hashX_mempool_status.stage_put((hashX,), (status,))
@@ -1463,6 +1478,8 @@ class BlockchainProcessorService(BlockchainService):
         self.pending_support_amount_change.clear()
         self.touched_hashXs.clear()
         self.mempool.clear()
+        self.hashX_history_cache.clear()
+        self.hashX_full_cache.clear()
 
     def backup_block(self):
         assert len(self.db.prefix_db._op_stack) == 0