base.cpp

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// Copyright (c) 2017-2018 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <chain.h>
#include <chainparams.h>
#include <config.h>
#include <index/base.h>
#include <node/blockstorage.h>
#include <node/ui_interface.h>
#include <shutdown.h>
#include <tinyformat.h>
#include <util/thread.h>
#include <util/translation.h>
#include <validation.h> // For CChainState
#include <warnings.h>
 
#include <functional>
 
using node::ReadBlockFromDisk;
 
constexpr char DB_BEST_BLOCK = 'B';
 
constexpr int64_t SYNC_LOG_INTERVAL = 30;           // secon
constexpr int64_t SYNC_LOCATOR_WRITE_INTERVAL = 30; // seconds
 
template <typename... Args>
static void FatalError(const char *fmt, const Args &...args) {
    std::string strMessage = tfm::format(fmt, args...);
    SetMiscWarning(Untranslated(strMessage));
    LogPrintf("*** %s\n", strMessage);
    AbortError(_("A fatal internal error occurred, see debug.log for details"));
    StartShutdown();
}
 
BaseIndex::DB::DB(const fs::path &path, size_t n_cache_size, bool f_memory,
                  bool f_wipe, bool f_obfuscate)
    : CDBWrapper(path, n_cache_size, f_memory, f_wipe, f_obfuscate) {}
 
bool BaseIndex::DB::ReadBestBlock(CBlockLocator &locator) const {
    bool success = Read(DB_BEST_BLOCK, locator);
    if (!success) {
        locator.SetNull();
    }
    return success;
}
 
void BaseIndex::DB::WriteBestBlock(CDBBatch &batch,
                                   const CBlockLocator &locator) {
    batch.Write(DB_BEST_BLOCK, locator);
}
 
BaseIndex::~BaseIndex() {
    Interrupt();
    Stop();
}
 
bool BaseIndex::Init() {
    CBlockLocator locator;
    if (!GetDB().ReadBestBlock(locator)) {
        locator.SetNull();
    }
 
    LOCK(cs_main);
    CChain &active_chain = m_chainstate->m_chain;
    if (locator.IsNull()) {
        m_best_block_index = nullptr;
    } else {
        m_best_block_index = m_chainstate->FindForkInGlobalIndex(locator);
    }
    m_synced = m_best_block_index.load() == active_chain.Tip();
    if (!m_synced) {
        bool prune_violation = false;
        if (!m_best_block_index) {
            // index is not built yet
            // make sure we have all block data back to the genesis
            prune_violation = node::GetFirstStoredBlock(active_chain.Tip()) !=
                              active_chain.Genesis();
        }
        // in case the index has a best block set and is not fully synced
        // check if we have the required blocks to continue building the index
        else {
            const CBlockIndex *block_to_test = m_best_block_index.load();
            if (!active_chain.Contains(block_to_test)) {
                // if the bestblock is not part of the mainchain, find the fork
                // and make sure we have all data down to the fork
                block_to_test = active_chain.FindFork(block_to_test);
            }
            const CBlockIndex *block = active_chain.Tip();
            prune_violation = true;
            // check backwards from the tip if we have all block data until we
            // reach the indexes bestblock
            while (block_to_test && block && block->nStatus.hasData()) {
                if (block_to_test == block) {
                    prune_violation = false;
                    break;
                }
                // block->pprev must exist at this point, since block_to_test is
                // part of the chain and thus must be encountered when going
                // backwards from the tip
                assert(block->pprev);
                block = block->pprev;
            }
        }
        if (prune_violation) {
            // throw error and graceful shutdown if we can't build the index
            FatalError("%s: %s best block of the index goes beyond pruned "
                       "data. Please disable the index or reindex (which will "
                       "download the whole blockchain again)",
                       __func__, GetName());
            return false;
        }
    }
    return true;
}
 
static const CBlockIndex *NextSyncBlock(const CBlockIndex *pindex_prev,
                                        CChain &chain)
    EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
    AssertLockHeld(cs_main);
 
    if (!pindex_prev) {
        return chain.Genesis();
    }
 
    const CBlockIndex *pindex = chain.Next(pindex_prev);
    if (pindex) {
        return pindex;
    }
 
    return chain.Next(chain.FindFork(pindex_prev));
}
 
void BaseIndex::ThreadSync() {
    const CBlockIndex *pindex = m_best_block_index.load();
    if (!m_synced) {
        auto &consensus_params = GetConfig().GetChainParams().GetConsensus();
 
        int64_t last_log_time = 0;
        int64_t last_locator_write_time = 0;
        while (true) {
            if (m_interrupt) {
                m_best_block_index = pindex;
                // No need to handle errors in Commit. If it fails, the error
                // will be already be logged. The best way to recover is to
                // continue, as index cannot be corrupted by a missed commit to
                // disk for an advanced index state.
                Commit();
                return;
            }
 
            {
                LOCK(cs_main);
                const CBlockIndex *pindex_next =
                    NextSyncBlock(pindex, m_chainstate->m_chain);
                if (!pindex_next) {
                    m_best_block_index = pindex;
                    m_synced = true;
                    // No need to handle errors in Commit. See rationale above.
                    Commit();
                    break;
                }
                if (pindex_next->pprev != pindex &&
                    !Rewind(pindex, pindex_next->pprev)) {
                    FatalError(
                        "%s: Failed to rewind index %s to a previous chain tip",
                        __func__, GetName());
                    return;
                }
                pindex = pindex_next;
            }
 
            int64_t current_time = GetTime();
            if (last_log_time + SYNC_LOG_INTERVAL < current_time) {
                LogPrintf("Syncing %s with block chain from height %d\n",
                          GetName(), pindex->nHeight);
                last_log_time = current_time;
            }
 
            if (last_locator_write_time + SYNC_LOCATOR_WRITE_INTERVAL <
                current_time) {
                m_best_block_index = pindex;
                last_locator_write_time = current_time;
                // No need to handle errors in Commit. See rationale above.
                Commit();
            }
 
            CBlock block;
            if (!ReadBlockFromDisk(block, pindex, consensus_params)) {
                FatalError("%s: Failed to read block %s from disk", __func__,
                           pindex->GetBlockHash().ToString());
                return;
            }
            if (!WriteBlock(block, pindex)) {
                FatalError("%s: Failed to write block %s to index database",
                           __func__, pindex->GetBlockHash().ToString());
                return;
            }
        }
    }
 
    if (pindex) {
        LogPrintf("%s is enabled at height %d\n", GetName(), pindex->nHeight);
    } else {
        LogPrintf("%s is enabled\n", GetName());
    }
}
 
bool BaseIndex::Commit() {
    CDBBatch batch(GetDB());
    if (!CommitInternal(batch) || !GetDB().WriteBatch(batch)) {
        return error("%s: Failed to commit latest %s state", __func__,
                     GetName());
    }
    return true;
}
 
bool BaseIndex::CommitInternal(CDBBatch &batch) {
    LOCK(cs_main);
    // Don't commit anything if we haven't indexed any block yet
    // (this could happen if init is interrupted).
    if (m_best_block_index == nullptr) {
        return false;
    }
    GetDB().WriteBestBlock(
        batch, m_chainstate->m_chain.GetLocator(m_best_block_index));
    return true;
}
 
bool BaseIndex::Rewind(const CBlockIndex *current_tip,
                       const CBlockIndex *new_tip) {
    assert(current_tip == m_best_block_index);
    assert(current_tip->GetAncestor(new_tip->nHeight) == new_tip);
 
    // In the case of a reorg, ensure persisted block locator is not stale.
    // Pruning has a minimum of 288 blocks-to-keep and getting the index
    // out of sync may be possible but a users fault.
    // In case we reorg beyond the pruned depth, ReadBlockFromDisk would
    // throw and lead to a graceful shutdown
    m_best_block_index = new_tip;
    if (!Commit()) {
        // If commit fails, revert the best block index to avoid corruption.
        m_best_block_index = current_tip;
        return false;
    }
 
    return true;
}
 
void BaseIndex::BlockConnected(const std::shared_ptr<const CBlock> &block,
                               const CBlockIndex *pindex) {
    if (!m_synced) {
        return;
    }
 
    const CBlockIndex *best_block_index = m_best_block_index.load();
    if (!best_block_index) {
        if (pindex->nHeight != 0) {
            FatalError("%s: First block connected is not the genesis block "
                       "(height=%d)",
                       __func__, pindex->nHeight);
            return;
        }
    } else {
        // Ensure block connects to an ancestor of the current best block. This
        // should be the case most of the time, but may not be immediately after
        // the the sync thread catches up and sets m_synced. Consider the case
        // where there is a reorg and the blocks on the stale branch are in the
        // ValidationInterface queue backlog even after the sync thread has
        // caught up to the new chain tip. In this unlikely event, log a warning
        // and let the queue clear.
        if (best_block_index->GetAncestor(pindex->nHeight - 1) !=
            pindex->pprev) {
            LogPrintf("%s: WARNING: Block %s does not connect to an ancestor "
                      "of known best chain (tip=%s); not updating index\n",
                      __func__, pindex->GetBlockHash().ToString(),
                      best_block_index->GetBlockHash().ToString());
            return;
        }
        if (best_block_index != pindex->pprev &&
            !Rewind(best_block_index, pindex->pprev)) {
            FatalError("%s: Failed to rewind index %s to a previous chain tip",
                       __func__, GetName());
            return;
        }
    }
 
    if (WriteBlock(*block, pindex)) {
        m_best_block_index = pindex;
    } else {
        FatalError("%s: Failed to write block %s to index", __func__,
                   pindex->GetBlockHash().ToString());
        return;
    }
}
 
void BaseIndex::ChainStateFlushed(const CBlockLocator &locator) {
    if (!m_synced) {
        return;
    }
 
    const BlockHash &locator_tip_hash = locator.vHave.front();
    const CBlockIndex *locator_tip_index;
    {
        LOCK(cs_main);
        locator_tip_index =
            m_chainstate->m_blockman.LookupBlockIndex(locator_tip_hash);
    }
 
    if (!locator_tip_index) {
        FatalError("%s: First block (hash=%s) in locator was not found",
                   __func__, locator_tip_hash.ToString());
        return;
    }
 
    // This checks that ChainStateFlushed callbacks are received after
    // BlockConnected. The check may fail immediately after the the sync thread
    // catches up and sets m_synced. Consider the case where there is a reorg
    // and the blocks on the stale branch are in the ValidationInterface queue
    // backlog even after the sync thread has caught up to the new chain tip. In
    // this unlikely event, log a warning and let the queue clear.
    const CBlockIndex *best_block_index = m_best_block_index.load();
    if (best_block_index->GetAncestor(locator_tip_index->nHeight) !=
        locator_tip_index) {
        LogPrintf("%s: WARNING: Locator contains block (hash=%s) not on known "
                  "best chain (tip=%s); not writing index locator\n",
                  __func__, locator_tip_hash.ToString(),
                  best_block_index->GetBlockHash().ToString());
        return;
    }
 
    // No need to handle errors in Commit. If it fails, the error will be
    // already be logged. The best way to recover is to continue, as index
    // cannot be corrupted by a missed commit to disk for an advanced index
    // state.
    Commit();
}
 
bool BaseIndex::BlockUntilSyncedToCurrentChain() const {
    AssertLockNotHeld(cs_main);
 
    if (!m_synced) {
        return false;
    }
 
    {
        // Skip the queue-draining stuff if we know we're caught up with
        // m_chain.Tip().
        LOCK(cs_main);
        const CBlockIndex *chain_tip = m_chainstate->m_chain.Tip();
        const CBlockIndex *best_block_index = m_best_block_index.load();
        if (best_block_index->GetAncestor(chain_tip->nHeight) == chain_tip) {
            return true;
        }
    }
 
    LogPrintf("%s: %s is catching up on block notifications\n", __func__,
              GetName());
    SyncWithValidationInterfaceQueue();
    return true;
}
 
void BaseIndex::Interrupt() {
    m_interrupt();
}
 
void BaseIndex::Start(CChainState &active_chainstate) {
    m_chainstate = &active_chainstate;
    // Need to register this ValidationInterface before running Init(), so that
    // callbacks are not missed if Init sets m_synced to true.
    RegisterValidationInterface(this);
    if (!Init()) {
        FatalError("%s: %s failed to initialize", __func__, GetName());
        return;
    }
 
    m_thread_sync =
        std::thread(&util::TraceThread, GetName(), [this] { ThreadSync(); });
}
 
void BaseIndex::Stop() {
    UnregisterValidationInterface(this);
 
    if (m_thread_sync.joinable()) {
        m_thread_sync.join();
    }
}
 
IndexSummary BaseIndex::GetSummary() const {
    IndexSummary summary{};
    summary.name = GetName();
    summary.synced = m_synced;
    summary.best_block_height =
        m_best_block_index ? m_best_block_index.load()->nHeight : 0;
    return summary;
}