chore(facade): Update SinkReplyBuilder2 (#3474)

src/facade/reply_builder.cc

@@ -193,28 +193,49 @@ size_t SinkReplyBuilder::UsedMemory() const {
   return dfly::HeapSize(batch_);
 }
 
-void SinkReplyBuilder2::Write(std::string_view str) {
-  DCHECK(scoped_);
-  if (str.size() >= 32)
-    WriteRef(str);
-  else
-    WritePiece(str);
+SinkReplyBuilder2::ReplyAggregator::~ReplyAggregator() {
+  rb->batched_ = prev;
+  if (!prev)
+    rb->Flush();
+}
+
+SinkReplyBuilder2::ReplyScope::~ReplyScope() {
+  rb->scoped_ = prev;
+  if (!prev)
+    rb->FinishScope();
+}
+
+void SinkReplyBuilder2::SendError(ErrorReply error) {
+  if (error.status)
+    return SendError(*error.status);
+  SendError(error.ToSv(), error.kind);
+}
+
+void SinkReplyBuilder2::SendError(OpStatus status) {
+  if (status == OpStatus::OK)
+    return SendOk();
+  SendError(StatusToMsg(status));
+}
+
+void SinkReplyBuilder2::CloseConnection() {
+  if (!ec_)
+    ec_ = std::make_error_code(std::errc::connection_aborted);
 }
 
 char* SinkReplyBuilder2::ReservePiece(size_t size) {
-  if (buffer_.AppendBuffer().size() <= size)
+  if (buffer_.AppendLen() <= size)
     Flush();
 
   char* dest = reinterpret_cast<char*>(buffer_.AppendBuffer().data());
-  if (vecs_.empty() || !IsInBuf(vecs_.back().iov_base))
+
+  // Start new vec for piece if last one dones't point at buffer tail
+  if (vecs_.empty() || ((char*)vecs_.back().iov_base) + vecs_.back().iov_len != dest)
     NextVec({dest, 0});
 
   return dest;
 }
 
 void SinkReplyBuilder2::CommitPiece(size_t size) {
-  DCHECK(IsInBuf(vecs_.back().iov_base));
-
   buffer_.CommitWrite(size);
   vecs_.back().iov_len += size;
   total_size_ += size;
@@ -232,30 +253,56 @@ void SinkReplyBuilder2::WriteRef(std::string_view str) {
 }
 
 void SinkReplyBuilder2::Flush() {
-  auto ec = sink_->Write(vecs_.data(), vecs_.size());
-  if (ec)
+  auto& reply_stats = tl_facade_stats->reply_stats;
+
+  send_active_ = true;
+  uint64_t before_ns = util::fb2::ProactorBase::GetMonotonicTimeNs();
+  reply_stats.io_write_cnt++;
+  reply_stats.io_write_bytes += total_size_;
+
+  if (auto ec = sink_->Write(vecs_.data(), vecs_.size()); ec)
     ec_ = ec;
 
+  uint64_t after_ns = util::fb2::ProactorBase::GetMonotonicTimeNs();
+  reply_stats.send_stats.count++;
+  reply_stats.send_stats.total_duration += (after_ns - before_ns) / 1'000;
+  send_active_ = false;
+
+  if (buffer_.InputLen() * 2 > buffer_.Capacity())  // If needed, grow backing buffer
+    buffer_.Reserve(std::min(kMaxBufferSize, buffer_.Capacity() * 2));
+
+  total_size_ = 0;
   buffer_.Clear();
   vecs_.clear();
-  total_size_ = 0;
+  guaranteed_pieces_ = 0;
 }
 
 void SinkReplyBuilder2::FinishScope() {
-  // If batching or aggregations are not enabled, flush
-  Flush();
+  if (!batched_ || total_size_ * 2 >= kMaxBufferSize)
+    return Flush();
 
-  // TODO: otherwise iterate over vec_ and copy items to buffer_
-  // whilst also updating their pointers
-}
+  // Check if we have enough space to copy all refs to buffer
+  size_t ref_bytes = total_size_ - buffer_.InputLen();
+  if (ref_bytes > buffer_.AppendLen())
+    return Flush();
 
-bool SinkReplyBuilder2::IsInBuf(const void* ptr) const {
+  // Copy all extenral references to buffer to safely keep batching
+  for (size_t i = guaranteed_pieces_; i < vecs_.size(); i++) {
     auto ib = buffer_.InputBuffer();
-  return ptr >= ib.data() && ptr <= ib.data() + ib.size();
+    if (vecs_[i].iov_base >= ib.data() && vecs_[i].iov_base <= ib.data() + ib.size())
+      continue;  // this is a piece
+
+    DCHECK_LE(buffer_.AppendLen(), vecs_[i].iov_len);
+    void* dest = buffer_.AppendBuffer().data();
+    memcpy(dest, vecs_[i].iov_base, vecs_[i].iov_len);
+    buffer_.CommitWrite(vecs_[i].iov_len);
+    vecs_[i].iov_base = dest;
+  }
+  guaranteed_pieces_ = vecs_.size();  // all vecs are pieces
 }
 
 void SinkReplyBuilder2::NextVec(std::string_view str) {
-  if (vecs_.size() >= IOV_MAX)
+  if (vecs_.size() >= IOV_MAX - 2)
     Flush();
   vecs_.push_back(iovec{const_cast<char*>(str.data()), str.size()});
 }

src/facade/reply_builder.h

@@ -167,34 +167,98 @@ class SinkReplyBuilder {
   bool send_active_ : 1;
 };
 
-// TMP: New version of reply builder that batches not only to a buffer, but also iovecs.
+// Base class for all reply builders. Offer a simple high level interface for controlling output
+// modes and sending basic response types.
 class SinkReplyBuilder2 {
-  explicit SinkReplyBuilder2(io::Sink* sink) : sink_(sink) {
-  }
-
-  // Use with care: All send calls within a scope must keep their data alive!
-  // This allows to fully eliminate copies for batches of data by using vectorized io.
-  struct ReplyScope {
-    explicit ReplyScope(SinkReplyBuilder2* rb) : prev_scoped(rb->scoped_), rb(rb) {
-      rb->scoped_ = true;
-    }
-    ~ReplyScope() {
-      if (!prev_scoped) {
-        rb->scoped_ = false;
-        rb->FinishScope();
-      }
-    }
-
-   private:
-    bool prev_scoped;
+  struct GuardBase {
+    bool prev;
     SinkReplyBuilder2* rb;
   };
 
  public:
-  void Write(std::string_view str);
+  constexpr static size_t kMaxInlineSize = 32;
+  constexpr static size_t kMaxBufferSize = 8192;
+
+  explicit SinkReplyBuilder2(io::Sink* sink) : sink_(sink) {
+  }
+
+  // USE WITH CARE! ReplyScope assumes that all string views in Send calls keep valid for the scopes
+  // lifetime. This allows the builder to avoid copies by enqueueing long strings directly for
+  // vectorized io.
+  struct ReplyScope : GuardBase {
+    explicit ReplyScope(SinkReplyBuilder2* rb) : GuardBase{std::exchange(rb->scoped_, true), rb} {
+    }
+
+    ~ReplyScope();
+  };
+
+  // Aggregator reduces the number of raw send calls by copying data in an intermediate buffer.
+  // Prefer ReplyScope if possible to additionally reduce the number of copies.
+  struct ReplyAggregator : GuardBase {
+    explicit ReplyAggregator(SinkReplyBuilder2* rb)
+        : GuardBase{std::exchange(rb->batched_, true), rb} {
+    }
+
+    ~ReplyAggregator();
+  };
+
+  void Flush();  // Send all accumulated data and reset to clear state
+
+  std::error_code GetError() const {
+    return ec_;
+  }
+
+  size_t UsedMemory() const {
+    return buffer_.Capacity();
+  }
+
+  bool IsSendActive() {
+    return send_active_;
+  }
+
+  void SetBatchMode(bool b) {
+    batched_ = b;
+  }
+
+  void CloseConnection();
+
+  static const ReplyStats& GetThreadLocalStats() {
+    return tl_facade_stats->reply_stats;
+  }
+
+  static void ResetThreadLocalStats() {
+    tl_facade_stats->reply_stats = {};
+  }
+
+ public:  // High level interface
+  virtual void SendLong(long val) = 0;
+  virtual void SendSimpleString(std::string_view str) = 0;
+
+  virtual void SendStored() = 0;
+  virtual void SendSetSkipped() = 0;
+  void SendOk() {
+    SendSimpleString("OK");
+  }
+
+  virtual void SendError(std::string_view str, std::string_view type = {}) = 0;  // MC and Redis
+  void SendError(OpStatus status);
+  void SendError(ErrorReply error);
+  virtual void SendProtocolError(std::string_view str) = 0;
 
  protected:
-  void Flush();        // Send all accumulated data and reset to clear state
+  void WriteI(std::string_view str) {
+    str.size() > kMaxInlineSize ? WriteRef(str) : WritePiece(str);
+  }
+
+  // Constexpr arrays are assumed to be protocol control sequences, stash them as pieces
+  template <size_t S> void WriteI(const char (&arr)[S]) {
+    WritePiece(std::string_view{arr, S - 1});  // we assume null termination
+  }
+
+  template <typename... Args> void Write(Args&&... strs) {
+    (WriteI(strs), ...);
+  }
+
   void FinishScope();  // Called when scope ends
 
   char* ReservePiece(size_t size);        // Reserve size bytes from buffer
@@ -202,19 +266,23 @@ class SinkReplyBuilder2 {
   void WritePiece(std::string_view str);  // Reserve + memcpy + Commit
 
   void WriteRef(std::string_view str);  // Add iovec bypassing buffer
-
-  bool IsInBuf(const void* ptr) const;  // checks if ptr is part of buffer_
   void NextVec(std::string_view str);
 
  private:
   io::Sink* sink_;
   std::error_code ec_;
 
-  bool scoped_;
+  bool send_active_ = false;
+  bool scoped_ = false, batched_ = false;
 
   size_t total_size_ = 0;  // sum of vec_ lengths
-  base::IoBuf buffer_;
-  std::vector<iovec> vecs_;
+  base::IoBuf buffer_;     // backing buffer for pieces
+
+  // Stores iovecs for a single writev call. Can reference either the buffer (WritePiece) or
+  // external data (WriteRef). Validity is ensured by FinishScope that either flushes before ref
+  // lifetime ends or copies refs to the buffer.
+  absl::InlinedVector<iovec, 16> vecs_;
+  size_t guaranteed_pieces_ = 0;  // length of prefix of vecs_ that are guaranteed to be pieces
 };
 
 class MCReplyBuilder : public SinkReplyBuilder {