refactor: Reduce number of LoadChainstate return values

Author: ryanofsky

src/bitcoin-chainstate.cpp

@@ -90,13 +90,13 @@ int main(int argc, char* argv[])
     cache_sizes.coins = (450 << 20) - (2 << 20) - (2 << 22);
     node::ChainstateLoadOptions options;
     options.check_interrupt = [] { return false; };
-    auto rv = node::LoadChainstate(chainman, cache_sizes, options);
-    if (rv.has_value()) {
+    auto [status, error] = node::LoadChainstate(chainman, cache_sizes, options);
+    if (status != node::ChainstateLoadStatus::SUCCESS) {
         std::cerr << "Failed to load Chain state from your datadir." << std::endl;
         goto epilogue;
     } else {
-        auto maybe_verify_error = node::VerifyLoadedChainstate(chainman, options);
-        if (maybe_verify_error.has_value()) {
+        std::tie(status, error) = node::VerifyLoadedChainstate(chainman, options);
+        if (status != node::ChainstateLoadStatus::SUCCESS) {
             std::cerr << "Failed to verify loaded Chain state from your datadir." << std::endl;
             goto epilogue;
         }

src/init.cpp

@@ -108,8 +108,6 @@ using kernel::DumpMempool;
 
 using node::CacheSizes;
 using node::CalculateCacheSizes;
-using node::ChainstateLoadVerifyError;
-using node::ChainstateLoadingError;
 using node::DEFAULT_PERSIST_MEMPOOL;
 using node::DEFAULT_PRINTPRIORITY;
 using node::DEFAULT_STOPAFTERBLOCKIMPORT;
@@ -1452,8 +1450,6 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         node.chainman = std::make_unique<ChainstateManager>(chainman_opts);
         ChainstateManager& chainman = *node.chainman;
 
-        bilingual_str strLoadError;
-
         node::ChainstateLoadOptions options;
         options.mempool = Assert(node.mempool.get());
         options.reindex = node::fReindex;
@@ -1470,87 +1466,38 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
         uiInterface.InitMessage(_("Loading block index…").translated);
         const int64_t load_block_index_start_time = GetTimeMillis();
-        std::optional<ChainstateLoadingError> maybe_load_error;
-        try {
-            maybe_load_error = LoadChainstate(chainman, cache_sizes, options);
-        } catch (const std::exception& e) {
-            LogPrintf("%s\n", e.what());
-            maybe_load_error = ChainstateLoadingError::ERROR_GENERIC_BLOCKDB_OPEN_FAILED;
-        }
-        if (maybe_load_error.has_value()) {
-            switch (maybe_load_error.value()) {
-            case ChainstateLoadingError::ERROR_LOADING_BLOCK_DB:
-                strLoadError = _("Error loading block database");
-                break;
-            case ChainstateLoadingError::ERROR_BAD_GENESIS_BLOCK:
-                // If the loaded chain has a wrong genesis, bail out immediately
-                // (we're likely using a testnet datadir, or the other way around).
-                return InitError(_("Incorrect or no genesis block found. Wrong datadir for network?"));
-            case ChainstateLoadingError::ERROR_PRUNED_NEEDS_REINDEX:
-                strLoadError = _("You need to rebuild the database using -reindex to go back to unpruned mode.  This will redownload the entire blockchain");
-                break;
-            case ChainstateLoadingError::ERROR_LOAD_GENESIS_BLOCK_FAILED:
-                strLoadError = _("Error initializing block database");
-                break;
-            case ChainstateLoadingError::ERROR_CHAINSTATE_UPGRADE_FAILED:
-                return InitError(_("Unsupported chainstate database format found. "
-                                   "Please restart with -reindex-chainstate. This will "
-                                   "rebuild the chainstate database."));
-            case ChainstateLoadingError::ERROR_REPLAYBLOCKS_FAILED:
-                strLoadError = _("Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.");
-                break;
-            case ChainstateLoadingError::ERROR_LOADCHAINTIP_FAILED:
-                strLoadError = _("Error initializing block database");
-                break;
-            case ChainstateLoadingError::ERROR_GENERIC_BLOCKDB_OPEN_FAILED:
-                strLoadError = _("Error opening block database");
-                break;
-            case ChainstateLoadingError::ERROR_BLOCKS_WITNESS_INSUFFICIENTLY_VALIDATED:
-                strLoadError = strprintf(_("Witness data for blocks after height %d requires validation. Please restart with -reindex."),
-                                         chainman.GetConsensus().SegwitHeight);
-                break;
-            case ChainstateLoadingError::SHUTDOWN_PROBED:
-                break;
-            }
-        } else {
-            std::optional<ChainstateLoadVerifyError> maybe_verify_error;
+        auto catch_exceptions = [](auto&& f) {
             try {
-                uiInterface.InitMessage(_("Verifying blocks…").translated);
-                if (chainman.m_blockman.m_have_pruned && options.check_blocks > MIN_BLOCKS_TO_KEEP) {
-                    LogPrintfCategory(BCLog::PRUNE, "pruned datadir may not have more than %d blocks; only checking available blocks\n",
-                                      MIN_BLOCKS_TO_KEEP);
-                }
-                maybe_verify_error = VerifyLoadedChainstate(chainman, options);
+                return f();
             } catch (const std::exception& e) {
                 LogPrintf("%s\n", e.what());
-                maybe_verify_error = ChainstateLoadVerifyError::ERROR_GENERIC_FAILURE;
+                return std::make_tuple(node::ChainstateLoadStatus::FAILURE, _("Error opening block database"));
             }
-            if (maybe_verify_error.has_value()) {
-                switch (maybe_verify_error.value()) {
-                case ChainstateLoadVerifyError::ERROR_BLOCK_FROM_FUTURE:
-                    strLoadError = _("The block database contains a block which appears to be from the future. "
-                                     "This may be due to your computer's date and time being set incorrectly. "
-                                     "Only rebuild the block database if you are sure that your computer's date and time are correct");
-                    break;
-                case ChainstateLoadVerifyError::ERROR_CORRUPTED_BLOCK_DB:
-                    strLoadError = _("Corrupted block database detected");
-                    break;
-                case ChainstateLoadVerifyError::ERROR_GENERIC_FAILURE:
-                    strLoadError = _("Error opening block database");
-                    break;
-                }
-            } else {
+        };
+        auto [status, error] = catch_exceptions([&]{ return LoadChainstate(chainman, cache_sizes, options); });
+        if (status == node::ChainstateLoadStatus::SUCCESS) {
+            uiInterface.InitMessage(_("Verifying blocks…").translated);
+            if (chainman.m_blockman.m_have_pruned && options.check_blocks > MIN_BLOCKS_TO_KEEP) {
+                LogPrintfCategory(BCLog::PRUNE, "pruned datadir may not have more than %d blocks; only checking available blocks\n",
+                                  MIN_BLOCKS_TO_KEEP);
+            }
+            std::tie(status, error) = catch_exceptions([&]{ return VerifyLoadedChainstate(chainman, options);});
+            if (status == node::ChainstateLoadStatus::SUCCESS) {
                 fLoaded = true;
                 LogPrintf(" block index %15dms\n", GetTimeMillis() - load_block_index_start_time);
             }
         }
 
+        if (status == node::ChainstateLoadStatus::FAILURE_INCOMPATIBLE_DB) {
+            return InitError(error);
+        }
+
         if (!fLoaded && !ShutdownRequested()) {
             // first suggest a reindex
             if (!options.reindex) {
                 bool fRet = uiInterface.ThreadSafeQuestion(
-                    strLoadError + Untranslated(".\n\n") + _("Do you want to rebuild the block database now?"),
-                    strLoadError.original + ".\nPlease restart with -reindex or -reindex-chainstate to recover.",
+                    error + Untranslated(".\n\n") + _("Do you want to rebuild the block database now?"),
+                    error.original + ".\nPlease restart with -reindex or -reindex-chainstate to recover.",
                     "", CClientUIInterface::MSG_ERROR | CClientUIInterface::BTN_ABORT);
                 if (fRet) {
                     fReindex = true;
@@ -1560,7 +1507,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
                     return false;
                 }
             } else {
-                return InitError(strLoadError);
+                return InitError(error);
             }
         }
     }

src/node/chainstate.cpp

@@ -23,8 +23,8 @@
 #include <vector>
 
 namespace node {
-std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman, const CacheSizes& cache_sizes,
-                                                     const ChainstateLoadOptions& options)
+ChainstateLoadResult LoadChainstate(ChainstateManager& chainman, const CacheSizes& cache_sizes,
+                                    const ChainstateLoadOptions& options)
 {
     auto is_coinsview_empty = [&](CChainState* chainstate) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
         return options.reindex || options.reindex_chainstate || chainstate->CoinsTip().GetBestBlock().IsNull();
@@ -49,34 +49,36 @@ std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman
         }
     }
 
-    if (options.check_interrupt && options.check_interrupt()) return ChainstateLoadingError::SHUTDOWN_PROBED;
+    if (options.check_interrupt && options.check_interrupt()) return {ChainstateLoadStatus::INTERRUPTED, {}};
 
     // LoadBlockIndex will load m_have_pruned if we've ever removed a
     // block file from disk.
     // Note that it also sets fReindex global based on the disk flag!
     // From here on, fReindex and options.reindex values may be different!
     if (!chainman.LoadBlockIndex()) {
-        if (options.check_interrupt && options.check_interrupt()) return ChainstateLoadingError::SHUTDOWN_PROBED;
-        return ChainstateLoadingError::ERROR_LOADING_BLOCK_DB;
+        if (options.check_interrupt && options.check_interrupt()) return {ChainstateLoadStatus::INTERRUPTED, {}};
+        return {ChainstateLoadStatus::FAILURE, _("Error loading block database")};
     }
 
     if (!chainman.BlockIndex().empty() &&
             !chainman.m_blockman.LookupBlockIndex(chainman.GetConsensus().hashGenesisBlock)) {
-        return ChainstateLoadingError::ERROR_BAD_GENESIS_BLOCK;
+        // If the loaded chain has a wrong genesis, bail out immediately
+        // (we're likely using a testnet datadir, or the other way around).
+        return {ChainstateLoadStatus::FAILURE_INCOMPATIBLE_DB, _("Incorrect or no genesis block found. Wrong datadir for network?")};
     }
 
     // Check for changed -prune state.  What we are concerned about is a user who has pruned blocks
     // in the past, but is now trying to run unpruned.
     if (chainman.m_blockman.m_have_pruned && !options.prune) {
-        return ChainstateLoadingError::ERROR_PRUNED_NEEDS_REINDEX;
+        return {ChainstateLoadStatus::FAILURE, _("You need to rebuild the database using -reindex to go back to unpruned mode.  This will redownload the entire blockchain")};
     }
 
     // At this point blocktree args are consistent with what's on disk.
     // If we're not mid-reindex (based on disk + args), add a genesis block on disk
     // (otherwise we use the one already on disk).
     // This is called again in ThreadImport after the reindex completes.
     if (!fReindex && !chainman.ActiveChainstate().LoadGenesisBlock()) {
-        return ChainstateLoadingError::ERROR_LOAD_GENESIS_BLOCK_FAILED;
+        return {ChainstateLoadStatus::FAILURE, _("Error initializing block database")};
     }
 
     // At this point we're either in reindex or we've loaded a useful
@@ -95,12 +97,14 @@ std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman
         // Refuse to load unsupported database format.
         // This is a no-op if we cleared the coinsviewdb with -reindex or -reindex-chainstate
         if (chainstate->CoinsDB().NeedsUpgrade()) {
-            return ChainstateLoadingError::ERROR_CHAINSTATE_UPGRADE_FAILED;
+            return {ChainstateLoadStatus::FAILURE_INCOMPATIBLE_DB, _("Unsupported chainstate database format found. "
+                                                                     "Please restart with -reindex-chainstate. This will "
+                                                                     "rebuild the chainstate database.")};
         }
 
         // ReplayBlocks is a no-op if we cleared the coinsviewdb with -reindex or -reindex-chainstate
         if (!chainstate->ReplayBlocks()) {
-            return ChainstateLoadingError::ERROR_REPLAYBLOCKS_FAILED;
+            return {ChainstateLoadStatus::FAILURE, _("Unable to replay blocks. You will need to rebuild the database using -reindex-chainstate.")};
         }
 
         // The on-disk coinsdb is now in a good state, create the cache
@@ -110,7 +114,7 @@ std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman
         if (!is_coinsview_empty(chainstate)) {
             // LoadChainTip initializes the chain based on CoinsTip()'s best block
             if (!chainstate->LoadChainTip()) {
-                return ChainstateLoadingError::ERROR_LOADCHAINTIP_FAILED;
+                return {ChainstateLoadStatus::FAILURE, _("Error initializing block database")};
             }
             assert(chainstate->m_chain.Tip() != nullptr);
         }
@@ -120,15 +124,15 @@ std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman
         auto chainstates{chainman.GetAll()};
         if (std::any_of(chainstates.begin(), chainstates.end(),
                         [](const CChainState* cs) EXCLUSIVE_LOCKS_REQUIRED(cs_main) { return cs->NeedsRedownload(); })) {
-            return ChainstateLoadingError::ERROR_BLOCKS_WITNESS_INSUFFICIENTLY_VALIDATED;
-        }
+            return {ChainstateLoadStatus::FAILURE, strprintf(_("Witness data for blocks after height %d requires validation. Please restart with -reindex."),
+                                                             chainman.GetConsensus().SegwitHeight)};
+        };
     }
 
-    return std::nullopt;
+    return {ChainstateLoadStatus::SUCCESS, {}};
 }
 
-std::optional<ChainstateLoadVerifyError> VerifyLoadedChainstate(ChainstateManager& chainman,
-                                                                const ChainstateLoadOptions& options)
+ChainstateLoadResult VerifyLoadedChainstate(ChainstateManager& chainman, const ChainstateLoadOptions& options)
 {
     auto is_coinsview_empty = [&](CChainState* chainstate) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
         return options.reindex || options.reindex_chainstate || chainstate->CoinsTip().GetBestBlock().IsNull();
@@ -140,18 +144,20 @@ std::optional<ChainstateLoadVerifyError> VerifyLoadedChainstate(ChainstateManage
         if (!is_coinsview_empty(chainstate)) {
             const CBlockIndex* tip = chainstate->m_chain.Tip();
             if (tip && tip->nTime > GetTime() + MAX_FUTURE_BLOCK_TIME) {
-                return ChainstateLoadVerifyError::ERROR_BLOCK_FROM_FUTURE;
+                return {ChainstateLoadStatus::FAILURE, _("The block database contains a block which appears to be from the future. "
+                                                         "This may be due to your computer's date and time being set incorrectly. "
+                                                         "Only rebuild the block database if you are sure that your computer's date and time are correct")};
             }
 
             if (!CVerifyDB().VerifyDB(
                     *chainstate, chainman.GetConsensus(), chainstate->CoinsDB(),
                     options.check_level,
                     options.check_blocks)) {
-                return ChainstateLoadVerifyError::ERROR_CORRUPTED_BLOCK_DB;
+                return {ChainstateLoadStatus::FAILURE, _("Corrupted block database detected")};
             }
         }
     }
 
-    return std::nullopt;
+    return {ChainstateLoadStatus::SUCCESS, {}};
 }
 } // namespace node

src/node/chainstate.h

@@ -31,18 +31,14 @@ struct ChainstateLoadOptions {
     std::function<void()> coins_error_cb;
 };
 
-enum class ChainstateLoadingError {
-    ERROR_LOADING_BLOCK_DB,
-    ERROR_BAD_GENESIS_BLOCK,
-    ERROR_PRUNED_NEEDS_REINDEX,
-    ERROR_LOAD_GENESIS_BLOCK_FAILED,
-    ERROR_CHAINSTATE_UPGRADE_FAILED,
-    ERROR_REPLAYBLOCKS_FAILED,
-    ERROR_LOADCHAINTIP_FAILED,
-    ERROR_GENERIC_BLOCKDB_OPEN_FAILED,
-    ERROR_BLOCKS_WITNESS_INSUFFICIENTLY_VALIDATED,
-    SHUTDOWN_PROBED,
-};
+//! Chainstate load status. Simple applications can just check for the success
+//! case, and treat other cases as errors. More complex applications may want to
+//! try reindexing in the generic failure case, and pass an interrupt callback
+//! and exit cleanly in the interrupted case.
+enum class ChainstateLoadStatus { SUCCESS, FAILURE, FAILURE_INCOMPATIBLE_DB, INTERRUPTED };
+
+//! Chainstate load status code and optional error string.
+using ChainstateLoadResult = std::tuple<ChainstateLoadStatus, bilingual_str>;
 
 /** This sequence can have 4 types of outcomes:
  *
@@ -55,32 +51,11 @@ enum class ChainstateLoadingError {
  *  4. Hard failure
  *    - a failure that definitively cannot be recovered from with a reindex
  *
- *  Currently, LoadChainstate returns a std::optional<ChainstateLoadingError>
- *  which:
- *
- *  - if has_value()
- *      - Either "Soft failure", "Hard failure", or "Shutdown requested",
- *        differentiable by the specific enumerator.
- *
- *        Note that a return value of SHUTDOWN_PROBED means ONLY that "during
- *        this sequence, when we explicitly checked shutdown_requested() at
- *        arbitrary points, one of those calls returned true". Therefore, a
- *        return value other than SHUTDOWN_PROBED does not guarantee that
- *        shutdown hasn't been called indirectly.
- *  - else
- *      - Success!
+ *  LoadChainstate returns a (status code, error string) tuple.
  */
-std::optional<ChainstateLoadingError> LoadChainstate(ChainstateManager& chainman, const CacheSizes& cache_sizes,
-                                                     const ChainstateLoadOptions& options);
-
-enum class ChainstateLoadVerifyError {
-    ERROR_BLOCK_FROM_FUTURE,
-    ERROR_CORRUPTED_BLOCK_DB,
-    ERROR_GENERIC_FAILURE,
-};
-
-std::optional<ChainstateLoadVerifyError> VerifyLoadedChainstate(ChainstateManager& chainman,
-                                                                const ChainstateLoadOptions& options);
+ChainstateLoadResult LoadChainstate(ChainstateManager& chainman, const CacheSizes& cache_sizes,
+                                    const ChainstateLoadOptions& options);
+ChainstateLoadResult VerifyLoadedChainstate(ChainstateManager& chainman, const ChainstateLoadOptions& options);
 } // namespace node
 
 #endif // BITCOIN_NODE_CHAINSTATE_H

src/test/util/setup_common.cpp

@@ -225,11 +225,11 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     options.prune = node::fPruneMode;
     options.check_blocks = m_args.GetIntArg("-checkblocks", DEFAULT_CHECKBLOCKS);
     options.check_level = m_args.GetIntArg("-checklevel", DEFAULT_CHECKLEVEL);
-    auto maybe_load_error = LoadChainstate(*Assert(m_node.chainman), m_cache_sizes, options);
-    assert(!maybe_load_error.has_value());
+    auto [status, error] = LoadChainstate(*Assert(m_node.chainman), m_cache_sizes, options);
+    assert(status == node::ChainstateLoadStatus::SUCCESS);
 
-    auto maybe_verify_error = VerifyLoadedChainstate(*Assert(m_node.chainman), options);
-    assert(!maybe_verify_error.has_value());
+    std::tie(status, error) = VerifyLoadedChainstate(*Assert(m_node.chainman), options);
+    assert(status == node::ChainstateLoadStatus::SUCCESS);
 
     BlockValidationState state;
     if (!m_node.chainman->ActiveChainstate().ActivateBestChain(state)) {