validation: allow to specify frequency for -checkblockindex

This makes it similar to -checkaddrman and -checkmempool, which
also allow to run the check occasionally instead of always / never.

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/init.cpp

@@ -604,7 +604,7 @@ void SetupServerArgs(ArgsManager& argsman)
 
     argsman.AddArg("-checkblocks=<n>", strprintf("How many blocks to check at startup (default: %u, 0 = all)", DEFAULT_CHECKBLOCKS), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-checklevel=<n>", strprintf("How thorough the block verification of -checkblocks is: %s (0-4, default: %u)", Join(CHECKLEVEL_DOC, ", "), DEFAULT_CHECKLEVEL), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
-    argsman.AddArg("-checkblockindex", strprintf("Do a consistency check for the block tree, chainstate, and other validation data structures occasionally. (default: %u, regtest: %u)", defaultChainParams->DefaultConsistencyChecks(), regtestChainParams->DefaultConsistencyChecks()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
+    argsman.AddArg("-checkblockindex", strprintf("Do a consistency check for the block tree, chainstate, and other validation data structures every <n> operations. Use 0 to disable. (default: %u, regtest: %u)", defaultChainParams->DefaultConsistencyChecks(), regtestChainParams->DefaultConsistencyChecks()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-checkaddrman=<n>", strprintf("Run addrman consistency checks every <n> operations. Use 0 to disable. (default: %u)", DEFAULT_ADDRMAN_CONSISTENCY_CHECKS), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-checkmempool=<n>", strprintf("Run mempool consistency checks every <n> transactions. Use 0 to disable. (default: %u, regtest: %u)", defaultChainParams->DefaultConsistencyChecks(), regtestChainParams->DefaultConsistencyChecks()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
     argsman.AddArg("-checkpoints", strprintf("Enable rejection of any forks from the known historical chain until block %s (default: %u)", defaultChainParams->Checkpoints().GetHeight(), DEFAULT_CHECKPOINTS_ENABLED), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);

src/kernel/chainstatemanager_opts.h

@@ -33,7 +33,7 @@ namespace kernel {
 struct ChainstateManagerOpts {
     const CChainParams& chainparams;
     fs::path datadir;
-    std::optional<bool> check_block_index{};
+    std::optional<int32_t> check_block_index{};
     bool checkpoints_enabled{DEFAULT_CHECKPOINTS_ENABLED};
     //! If set, it will override the minimum work we will assume exists on some valid chain.
     std::optional<arith_uint256> minimum_chain_work{};

src/node/chainstatemanager_args.cpp

@@ -24,7 +24,10 @@
 namespace node {
 util::Result<void> ApplyArgsManOptions(const ArgsManager& args, ChainstateManager::Options& opts)
 {
-    if (auto value{args.GetBoolArg("-checkblockindex")}) opts.check_block_index = *value;
+    if (auto value{args.GetIntArg("-checkblockindex")}) {
+        // Interpret bare -checkblockindex argument as 1 instead of 0.
+        opts.check_block_index = args.GetArg("-checkblockindex")->empty() ? 1 : *value;
+    }
 
     if (auto value{args.GetBoolArg("-checkpoints")}) opts.checkpoints_enabled = *value;
 

src/test/util/setup_common.cpp

@@ -238,7 +238,7 @@ ChainTestingSetup::ChainTestingSetup(const ChainType chainType, const std::vecto
     const ChainstateManager::Options chainman_opts{
         .chainparams = chainparams,
         .datadir = m_args.GetDataDirNet(),
-        .check_block_index = true,
+        .check_block_index = 1,
         .notifications = *m_node.notifications,
         .signals = m_node.validation_signals.get(),
         .worker_threads_num = 2,

src/validation.cpp

@@ -5034,6 +5034,14 @@ void ChainstateManager::LoadExternalBlockFile(
     LogPrintf("Loaded %i blocks from external file in %dms\n", nLoaded, Ticks<std::chrono::milliseconds>(SteadyClock::now() - start));
 }
 
+bool ChainstateManager::ShouldCheckBlockIndex() const
+{
+    // Assert to verify Flatten() has been called.
+    if (!*Assert(m_options.check_block_index)) return false;
+    if (GetRand(*m_options.check_block_index) >= 1) return false;
+    return true;
+}
+
 void ChainstateManager::CheckBlockIndex()
 {
     if (!ShouldCheckBlockIndex()) {

src/validation.h

@@ -933,7 +933,7 @@ public:
 
     const CChainParams& GetParams() const { return m_options.chainparams; }
     const Consensus::Params& GetConsensus() const { return m_options.chainparams.GetConsensus(); }
-    bool ShouldCheckBlockIndex() const { return *Assert(m_options.check_block_index); }
+    bool ShouldCheckBlockIndex() const;
     const arith_uint256& MinimumChainWork() const { return *Assert(m_options.minimum_chain_work); }
     const uint256& AssumedValidBlock() const { return *Assert(m_options.assumed_valid_block); }
     kernel::Notifications& GetNotifications() const { return m_options.notifications; };