Method FindFilesToPrune

src/node/blockstorage.cpp:332–411

}

void BlockManager::FindFilesToPrune(
    std::set<int>& setFilesToPrune,
    int last_prune,
    const Chainstate& chain,
    ChainstateManager& chainman)
{
    LOCK(::cs_main);
    // Compute `target` value with maximum size (in bytes) of blocks below the
    // `last_prune` height which should be preserved and not pruned. The
    // `target` value will be derived from the -prune preference provided by the
    // user. If there is a historical chainstate being used to populate indexes
    // and validate the snapshot, the target is divided by two so half of the
    // block storage will be reserved for the historical chainstate, and the
    // other half will be reserved for the most-work chainstate.
    const int num_chainstates{chainman.HistoricalChainstate() ? 2 : 1};
    const auto target = std::max(
        MIN_DISK_SPACE_FOR_BLOCK_FILES, GetPruneTarget() / num_chainstates);
    const uint64_t target_sync_height = chainman.m_best_header->nHeight;

    if (chain.m_chain.Height() < 0 || target == 0) {
        return;
    }
    if (static_cast<uint64_t>(chain.m_chain.Height()) <= chainman.GetParams().PruneAfterHeight()) {
        return;
    }

    const auto [min_block_to_prune, last_block_can_prune] = chain.GetPruneRange(last_prune);

    uint64_t nCurrentUsage = CalculateCurrentUsage();
    // We don't check to prune until after we've allocated new space for files
    // So we should leave a buffer under our target to account for another allocation
    // before the next pruning.
    uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
    uint64_t nBytesToPrune;
    int count = 0;

    if (nCurrentUsage + nBuffer >= target) {
        // On a prune event, the chainstate DB is flushed.
        // To avoid excessive prune events negating the benefit of high dbcache
        // values, we should not prune too rapidly.
        // So when pruning in IBD, increase the buffer to avoid a re-prune too soon.
        const auto chain_tip_height = chain.m_chain.Height();
        if (chainman.IsInitialBlockDownload() && target_sync_height > (uint64_t)chain_tip_height) {
            // Since this is only relevant during IBD, we assume blocks are at least 1 MB on average
            static constexpr uint64_t average_block_size = 1000000;  /* 1 MB */
            const uint64_t remaining_blocks = target_sync_height - chain_tip_height;
            nBuffer += average_block_size * remaining_blocks;
        }

        for (int fileNumber = 0; fileNumber < this->MaxBlockfileNum(); fileNumber++) {
            const auto& fileinfo = m_blockfile_info[fileNumber];
            nBytesToPrune = fileinfo.nSize + fileinfo.nUndoSize;

            if (fileinfo.nSize == 0) {
                continue;
            }

            if (nCurrentUsage + nBuffer < target) { // are we below our target?