Add connection context that will serve us as an interface between command handler and the service

server/CMakeLists.txt

@@ -2,8 +2,8 @@ add_executable(dragonfly dfly_main.cc)
 cxx_link(dragonfly base dragonfly_lib)
 
 add_library(dragonfly_lib db_slice.cc dragonfly_listener.cc dragonfly_connection.cc 
-            main_service.cc engine_shard_set.cc
-            redis_parser.cc resp_expr.cc)
+            main_service.cc engine_shard_set.cc 
+            redis_parser.cc resp_expr.cc reply_builder.cc)
 
 cxx_link(dragonfly_lib uring_fiber_lib
          fibers_ext strings_lib http_server_lib)

server/conn_context.h

@@ -0,0 +1,28 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+
+#pragma once
+
+#include "server/reply_builder.h"
+
+namespace dfly {
+
+class Connection;
+class EngineShardSet;
+
+class ConnectionContext : public ReplyBuilder {
+ public:
+  ConnectionContext(::io::Sink* stream, Connection* owner) : ReplyBuilder(stream), owner_(owner) {
+  }
+
+  // TODO: to introduce proper accessors.
+  EngineShardSet* shard_set = nullptr;
+
+  Connection* owner() { return owner_;}
+
+ private:
+  Connection* owner_;
+};
+
+}  // namespace dfly

server/dragonfly_connection.cc

@@ -10,6 +10,7 @@
 #include "base/logging.h"
 #include "server/main_service.h"
 #include "server/redis_parser.h"
+#include "server/conn_context.h"
 #include "util/fiber_sched_algo.h"
 
 using namespace util;
@@ -79,6 +80,9 @@ void Connection::HandleRequests() {
   CHECK_EQ(0, setsockopt(socket_->native_handle(), SOL_TCP, TCP_NODELAY, &val, sizeof(val)));
 
   FiberSocketBase* peer = socket_.get();
+  cc_.reset(new ConnectionContext(peer, this));
+  cc_->shard_set = &service_->shard_set();
+
   InputLoop(peer);
 
   VLOG(1) << "Closed connection for peer " << socket_->RemoteEndpoint();
@@ -100,7 +104,7 @@ void Connection::InputLoop(FiberSocketBase* peer) {
     }
 
     io_buf.CommitWrite(*recv_sz);
-    status = ParseRedis(&io_buf, peer);
+    status = ParseRedis(&io_buf);
      if (status == NEED_MORE) {
       status = OK;
     } else if (status != OK) {
@@ -113,12 +117,12 @@ void Connection::InputLoop(FiberSocketBase* peer) {
   }
 }
 
-auto Connection::ParseRedis(base::IoBuf* io_buf, util::FiberSocketBase* peer) -> ParserStatus {
+auto Connection::ParseRedis(base::IoBuf* io_buf) -> ParserStatus {
   RespVec args;
   uint32_t consumed = 0;
 
   RedisParser::Result result = RedisParser::OK;
-  error_code ec;
+
   do {
     result = redis_parser_->Parse(io_buf->InputBuffer(), &consumed, &args);
 
@@ -131,15 +135,15 @@ auto Connection::ParseRedis(base::IoBuf* io_buf, util::FiberSocketBase* peer) ->
       CHECK_EQ(RespExpr::STRING, first.type);  // TODO
       string_view sv = ToSV(first.GetBuf());
       if (sv == "PING") {
-        ec = peer->Write(io::Buffer("PONG\r\n"));
+        cc_->SendSimpleString("PONG");
       } else if (sv == "SET") {
         CHECK_EQ(3u, args.size());
         service_->Set(ToSV(args[1].GetBuf()), ToSV(args[2].GetBuf()));
-        ec = peer->Write(io::Buffer("OK\r\n"));
+        cc_->SendOk();
       }
     }
     io_buf->ConsumeInput(consumed);
-  } while (RedisParser::OK == result && !ec);
+  } while (RedisParser::OK == result && !cc_->ec());
 
   parser_error_ = result;
   if (result == RedisParser::OK)

server/dragonfly_connection.h

@@ -12,6 +12,7 @@ namespace dfly {
 
 class Service;
 class RedisParser;
+class ConnectionContext;
 
 class Connection : public util::Connection {
  public:
@@ -35,11 +36,14 @@ class Connection : public util::Connection {
 
   void InputLoop(util::FiberSocketBase* peer);
 
-  ParserStatus ParseRedis(base::IoBuf* buf, util::FiberSocketBase* peer);
+  ParserStatus ParseRedis(base::IoBuf* buf);
 
   std::unique_ptr<RedisParser> redis_parser_;
+  std::unique_ptr<ConnectionContext> cc_;
+
   Service* service_;
   unsigned parser_error_ = 0;
+
   struct Shutdown;
   std::unique_ptr<Shutdown> shutdown_;
 };

server/reply_builder.cc

@@ -0,0 +1,99 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#include "server/reply_builder.h"
+
+#include <absl/strings/numbers.h>
+#include <absl/strings/str_cat.h>
+
+#include "base/logging.h"
+
+using namespace std;
+using absl::StrAppend;
+
+namespace dfly {
+
+namespace {
+
+inline iovec constexpr IoVec(std::string_view s) {
+  iovec r{const_cast<char*>(s.data()), s.size()};
+  return r;
+}
+
+constexpr char kCRLF[] = "\r\n";
+constexpr char kErrPref[] = "-ERR ";
+constexpr char kSimplePref[] = "+";
+
+}  // namespace
+
+RespSerializer::RespSerializer(io::Sink* stream) : sink_(stream) {
+}
+
+void RespSerializer::Send(const iovec* v, uint32_t len) {
+  error_code ec = sink_->Write(v, len);
+  if (ec) {
+    ec_ = ec;
+  }
+}
+
+void RespSerializer::SendDirect(std::string_view raw) {
+  iovec v = {IoVec(raw)};
+
+  Send(&v, 1);
+}
+
+void ReplyBuilder::SendBulkString(std::string_view str) {
+  char tmp[absl::numbers_internal::kFastToBufferSize + 3];
+  tmp[0] = '$';  // Format length
+  char* next = absl::numbers_internal::FastIntToBuffer(uint32_t(str.size()), tmp + 1);
+  *next++ = '\r';
+  *next++ = '\n';
+
+  std::string_view lenpref{tmp, size_t(next - tmp)};
+
+  // 3 parts: length, string and CRLF.
+  iovec v[3] = {IoVec(lenpref), IoVec(str), IoVec(kCRLF)};
+
+  return Send(v, ABSL_ARRAYSIZE(v));
+}
+
+void ReplyBuilder::SendError(std::string_view str) {
+  if (str[0] == '-') {
+    iovec v[] = {IoVec(str), IoVec(kCRLF)};
+    return Send(v, ABSL_ARRAYSIZE(v));
+  } else {
+    iovec v[] = {IoVec(kErrPref), IoVec(str), IoVec(kCRLF)};
+    return Send(v, ABSL_ARRAYSIZE(v));
+  }
+}
+
+void ReplyBuilder::SendError(OpStatus status) {
+  switch (status) {
+    case OpStatus::OK:
+      SendOk();
+      break;
+    case OpStatus::KEY_NOTFOUND:
+      SendError("no such key");
+      break;
+    default:
+      LOG(ERROR) << "Unsupported status " << status;
+      SendError("Internal error");
+      break;
+  }
+}
+
+void ReplyBuilder::SendNull() {
+  constexpr char kNullStr[] = "$-1\r\n";
+
+  iovec v[] = {IoVec(kNullStr)};
+
+  Send(v, ABSL_ARRAYSIZE(v));
+}
+
+void ReplyBuilder::SendSimpleString(std::string_view str) {
+  iovec v[3] = {IoVec(kSimplePref), IoVec(str), IoVec(kCRLF)};
+
+  Send(v, ABSL_ARRAYSIZE(v));
+}
+
+}  // namespace dfly

server/reply_builder.h

@@ -0,0 +1,63 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#include <string_view>
+#include <optional>
+
+#include "io/sync_stream_interface.h"
+
+#include "server/op_status.h"
+
+namespace dfly {
+
+class RespSerializer {
+ public:
+  explicit RespSerializer(::io::Sink* sink);
+
+  std::error_code ec() const {
+    return ec_;
+  }
+
+  void CloseConnection() {
+    if (!ec_)
+      ec_ = std::make_error_code(std::errc::connection_aborted);
+  }
+
+  //! Sends a string as is without any formatting. raw should be RESP-encoded.
+  void SendDirect(std::string_view str);
+
+  ::io::Sink* sink() { return sink_; }
+
+ protected:
+  void Send(const iovec* v, uint32_t len);
+
+  ::io::Sink* sink_;
+
+ private:
+  std::error_code ec_;
+};
+
+class ReplyBuilder : public RespSerializer {
+ public:
+  explicit ReplyBuilder(::io::Sink* stream) : RespSerializer(stream) {
+  }
+
+  /// aka "$6\r\nfoobar\r\n"
+  void SendBulkString(std::string_view str);
+
+  void SendNull();
+
+  void SendOk() {
+    return SendSimpleString("OK");
+  }
+
+  void SendError(std::string_view str);
+  void SendError(OpStatus status);
+
+  //! See https://redis.io/topics/protocol
+  void SendSimpleString(std::string_view str);
+
+private:
+};
+
+}  // namespace dfly