uint32_t BlockCache::onRegionReclaim()

in cachelib/navy/block_cache/BlockCache.cpp [296:357]
48 lines of code
10 McCabe index (conditional complexity)

uint32_t BlockCache::onRegionReclaim(RegionId rid, BufferView buffer) {
  // Eviction callback guarantees are the following:
  //   - Every value inserted will get eviction callback at some point of
  //     time.
  //   - It is invoked only once per insertion.
  //
  // We do not guarantee time between remove and callback invocation. If a
  // value v1 was replaced with v2 user will get callbacks for both v1 and
  // v2 when they are evicted (in no particular order).
  uint32_t evictionCount = 0; // item that was evicted during reclaim
  auto& region = regionManager_.getRegion(rid);
  auto offset = region.getLastEntryEndOffset();
  while (offset > 0) {
    auto entryEnd = buffer.data() + offset;
    auto desc =
        *reinterpret_cast<const EntryDesc*>(entryEnd - sizeof(EntryDesc));
    if (desc.csSelf != desc.computeChecksum()) {
      reclaimEntryHeaderChecksumErrorCount_.inc();
      XLOGF(ERR,
            "Item header checksum mismatch. Region {} is likely corrupted. "
            "Expected:{}, Actual: {}. Aborting reclaim. Remaining items in the "
            "region will not be cleaned up (destructor won't be invoked).",
            rid.index(),
            desc.csSelf,
            desc.computeChecksum());
      break;
    }

    const auto entrySize = serializedSize(desc.keySize, desc.valueSize);
    HashedKey hk{
        BufferView{desc.keySize, entryEnd - sizeof(EntryDesc) - desc.keySize}};
    BufferView value{desc.valueSize, entryEnd - entrySize};
    if (checksumData_ && desc.cs != checksum(value)) {
      // We do not need to abort here since the EntryDesc checksum was good, so
      // we can safely proceed to read the next entry.
      reclaimValueChecksumErrorCount_.inc();
    }

    const auto reinsertionRes =
        reinsertOrRemoveItem(hk, value, entrySize, RelAddress{rid, offset});
    switch (reinsertionRes) {
    case ReinsertionRes::kEvicted:
      evictionCount++;
      break;
    case ReinsertionRes::kRemoved:
      holeCount_.sub(1);
      holeSizeTotal_.sub(decodeSizeHint(encodeSizeHint(entrySize)));
      break;
    case ReinsertionRes::kReinserted:
      break;
    }

    if (destructorCb_ && reinsertionRes == ReinsertionRes::kEvicted) {
      destructorCb_(hk.key(), value, DestructorEvent::Recycled);
    }
    XDCHECK_GE(offset, entrySize);
    offset -= entrySize;
  }

  XDCHECK_GE(region.getNumItems(), evictionCount);
  return evictionCount;
}