P2PServer: delete old cached blocks after initial sync

Saves ~20 MB of memory

src/p2p_server.cpp

@@ -102,14 +102,11 @@ P2PServer::~P2PServer()
 	uv_mutex_destroy(&m_peerListLock);
 	uv_mutex_destroy(&m_broadcastLock);
 	uv_mutex_destroy(&m_missingBlockRequestsLock);
+
+	clear_cached_blocks();
 	uv_rwlock_destroy(&m_cachedBlocksLock);
 
 	delete m_block;
-
-	for (auto it : m_cachedBlocks) {
-		delete it.second;
-	}
-
 	delete m_cache;
 }
 
@@ -124,6 +121,16 @@ void P2PServer::add_cached_block(const PoolBlock& block)
 	m_cachedBlocks.insert({ new_block->m_sidechainId, new_block });
 }
 
+void P2PServer::clear_cached_blocks()
+{
+	WriteLock lock(m_cachedBlocksLock);
+
+	for (auto it : m_cachedBlocks) {
+		delete it.second;
+	}
+	m_cachedBlocks.clear();
+}
+
 void P2PServer::store_in_cache(const PoolBlock& block)
 {
 	if (m_cache && block.m_verified && !block.m_invalid) {