Add cache to CQuorumManager::ScanQuorums (#2856)

Author: codablock

src/llmq/quorums.cpp

@@ -311,9 +311,29 @@ std::vector<CQuorumCPtr> CQuorumManager::ScanQuorums(Consensus::LLMQType llmqTyp
 {
     auto& params = Params().GetConsensus().llmqs.at(llmqType);
 
-    auto quorumIndexes = quorumBlockProcessor->GetMinedCommitmentsUntilBlock(params.type, pindexStart, maxCount);
+    auto cacheKey = std::make_pair(llmqType, pindexStart->GetBlockHash());
+    const size_t cacheMaxSize = 25; // largest active set + 1
 
     std::vector<CQuorumCPtr> result;
+
+    if (maxCount <= cacheMaxSize) {
+        LOCK(quorumsCacheCs);
+        if (scanQuorumsCache.get(cacheKey, result)) {
+            if (result.size() > maxCount) {
+                result.resize(maxCount);
+            }
+            return result;
+        }
+    }
+
+    bool storeCache = false;
+    size_t maxCount2 = maxCount;
+    if (maxCount2 <= cacheMaxSize) {
+        maxCount2 = cacheMaxSize;
+        storeCache = true;
+    }
+
+    auto quorumIndexes = quorumBlockProcessor->GetMinedCommitmentsUntilBlock(params.type, pindexStart, maxCount2);
     result.reserve(quorumIndexes.size());
 
     for (auto& quorumIndex : quorumIndexes) {
@@ -323,6 +343,15 @@ std::vector<CQuorumCPtr> CQuorumManager::ScanQuorums(Consensus::LLMQType llmqTyp
         result.emplace_back(quorum);
     }
 
+    if (storeCache) {
+        LOCK(quorumsCacheCs);
+        scanQuorumsCache.insert(cacheKey, result);
+    }
+
+    if (result.size() > maxCount) {
+        result.resize(maxCount);
+    }
+
     return result;
 }
 

src/llmq/quorums.h

@@ -11,6 +11,8 @@
 
 #include "validationinterface.h"
 #include "consensus/params.h"
+#include "saltedhasher.h"
+#include "unordered_lru_cache.h"
 
 #include "bls/bls.h"
 #include "bls/bls_worker.h"
@@ -85,6 +87,7 @@ class CQuorumManager
 
     CCriticalSection quorumsCacheCs;
     std::map<std::pair<Consensus::LLMQType, uint256>, CQuorumPtr> quorumsCache;
+    unordered_lru_cache<std::pair<Consensus::LLMQType, uint256>, std::vector<CQuorumCPtr>, StaticSaltedHasher, 32> scanQuorumsCache;
 
 public:
     CQuorumManager(CEvoDB& _evoDb, CBLSWorker& _blsWorker, CDKGSessionManager& _dkgManager);