Add -pausebackgroundsync startup option

When a UTXO snapshot is loaded, this option lets the user pause the verification of historical blocks in the background.

doc/release-notes-31023.md

@@ -0,0 +1,4 @@
+Updated settings
+------
+
+- When loading an assumeutxo snapshot, the background sync can be paused with `-pausebackgroundsync`. (#31023)

src/init.cpp

@@ -489,6 +489,7 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     argsman.AddArg("-minimumchainwork=<hex>", strprintf("Minimum work assumed to exist on a valid chain in hex (default: %s, testnet3: %s, testnet4: %s, signet: %s)", defaultChainParams->GetConsensus().nMinimumChainWork.GetHex(), testnetChainParams->GetConsensus().nMinimumChainWork.GetHex(), testnet4ChainParams->GetConsensus().nMinimumChainWork.GetHex(), signetChainParams->GetConsensus().nMinimumChainWork.GetHex()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::OPTIONS);
     argsman.AddArg("-par=<n>", strprintf("Set the number of script verification threads (0 = auto, up to %d, <0 = leave that many cores free, default: %d)",
         MAX_SCRIPTCHECK_THREADS, DEFAULT_SCRIPTCHECK_THREADS), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-pausebackgroundsync", strprintf("When a UTXO snapshot is loaded, pause the verification of historical blocks in the background (default: %u)", DEFAULT_PAUSE_BACKGROUND_SYNC), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-persistmempool", strprintf("Whether to save the mempool on shutdown and load on restart (default: %u)", DEFAULT_PERSIST_MEMPOOL), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-persistmempoolv1",
                    strprintf("Whether a mempool.dat file created by -persistmempool or the savemempool RPC will be written in the legacy format "

src/kernel/chainstatemanager_opts.h

@@ -52,6 +52,8 @@ struct ChainstateManagerOpts {
     int worker_threads_num{0};
     size_t script_execution_cache_bytes{DEFAULT_SCRIPT_EXECUTION_CACHE_BYTES};
     size_t signature_cache_bytes{DEFAULT_SIGNATURE_CACHE_BYTES};
+    //! Whether to defer syncing the background chainstate after an assumeutxo snapshot is loaded
+    bool pause_background_sync{false};
 };
 
 } // namespace kernel

src/node/chainstatemanager_args.cpp

@@ -73,6 +73,8 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& args, ChainstateManage
         opts.signature_cache_bytes = clamped_size_each;
     }
 
+    opts.pause_background_sync = args.GetBoolArg("-pausebackgroundsync", DEFAULT_PAUSE_BACKGROUND_SYNC);
+
     return {};
 }
 } // namespace node

src/node/chainstatemanager_args.h

@@ -14,6 +14,8 @@ class ArgsManager;
 static constexpr int MAX_SCRIPTCHECK_THREADS{15};
 /** -par default (number of script-checking threads, 0 = auto) */
 static constexpr int DEFAULT_SCRIPTCHECK_THREADS{0};
+/** -pausebackgroundsync default */
+static const bool DEFAULT_PAUSE_BACKGROUND_SYNC{false};
 
 namespace node {
 [[nodiscard]] util::Result<void> ApplyArgsManOptions(const ArgsManager& args, ChainstateManager::Options& opts);

src/validation.cpp

@@ -6387,6 +6387,12 @@ std::optional<int> ChainstateManager::GetSnapshotBaseHeight() const
     return base ? std::make_optional(base->nHeight) : std::nullopt;
 }
 
+bool ChainstateManager::BackgroundSyncInProgress() const EXCLUSIVE_LOCKS_REQUIRED(GetMutex()) {
+    if (!IsUsable(m_snapshot_chainstate.get())) return false;
+    if (!IsUsable(m_ibd_chainstate.get())) return false;
+    return !m_options.pause_background_sync;
+}
+
 bool ChainstateManager::ValidatedSnapshotCleanup()
 {
     AssertLockHeld(::cs_main);

src/validation.h

@@ -1113,9 +1113,7 @@ class ChainstateManager
     CBlockIndex* ActiveTip() const EXCLUSIVE_LOCKS_REQUIRED(GetMutex()) { return ActiveChain().Tip(); }
 
     //! The state of a background sync (for net processing)
-    bool BackgroundSyncInProgress() const EXCLUSIVE_LOCKS_REQUIRED(GetMutex()) {
-        return IsUsable(m_snapshot_chainstate.get()) && IsUsable(m_ibd_chainstate.get());
-    }
+    bool BackgroundSyncInProgress() const EXCLUSIVE_LOCKS_REQUIRED(GetMutex());
 
     //! The tip of the background sync chain
     const CBlockIndex* GetBackgroundSyncTip() const EXCLUSIVE_LOCKS_REQUIRED(GetMutex()) {