processor.h

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/*
  Copyright (c) 2022, 2025, Oracle and/or its affiliates.
 
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  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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*/
 
#ifndef ROUTING_CLASSIC_PROCESSOR_INCLUDED
#define ROUTING_CLASSIC_PROCESSOR_INCLUDED
 
#include "basic_protocol_splicer.h"
 
#include "trace_span.h"
#include "tracer.h"
 
class MysqlRoutingClassicConnectionBase;
class ClassicProtocolState;
 
/**
 * base class of all the processors.
 *
 * Processor
 *
 * - have their own internal state
 * - expose a process() function which will be called until
 *   it returns Result::Done
 *
 * Processors are stacked.
 *
 * The methods:
 *
 * - push_processor()
 * - pop_processor()
 *
 * allow to add and remove elements for the stack.
 *
 * The top-most processor's process() function is called.
 */
class BasicProcessor {
 public:
  enum class Result {
    Again,           // will invoke the process() of the top-most-processor
    RecvFromClient,  // wait for recv from client and invoke ...
    SendToClient,    // wait for send-to-client and invoke ...
    RecvFromServer,  // wait for recv from server and invoke ...
    RecvFromBoth,    // wait for recv from client and server and invoke ..
    SendToServer,    // wait for send-to-server and invoke ...
    SendableToServer,
 
    Suspend,  // wait for explicit resume
    Done,  // pop this processor and invoke the top-most-processor's process()
 
    Void,
  };
 
  BasicProcessor(MysqlRoutingClassicConnectionBase *conn) : conn_(conn) {}
 
  virtual ~BasicProcessor() = default;
 
  const MysqlRoutingClassicConnectionBase *connection() const { return conn_; }
 
  MysqlRoutingClassicConnectionBase *connection() { return conn_; }
 
  virtual stdx::expected<Result, std::error_code> process() = 0;
 
 private:
  MysqlRoutingClassicConnectionBase *conn_;
};
 
/**
 * a processor base class with helper functions.
 */
class Processor : public BasicProcessor {
 public:
  using BasicProcessor::BasicProcessor;
 
 protected:
  stdx::expected<Result, std::error_code> send_server_failed(
      std::error_code ec);
 
  stdx::expected<Result, std::error_code> recv_server_failed(
      std::error_code ec);
 
  stdx::expected<Result, std::error_code> send_client_failed(
      std::error_code ec);
 
  stdx::expected<Result, std::error_code> recv_client_failed(
      std::error_code ec);
 
  stdx::expected<Result, std::error_code> server_socket_failed(
      std::error_code ec);
 
  stdx::expected<Result, std::error_code> client_socket_failed(
      std::error_code ec);
 
  /**
   * discard to current message.
   *
   * @pre ensure_full_frame() must true.
   */
  stdx::expected<void, std::error_code> discard_current_msg(
      Channel &src_channel, ClassicProtocolState &src_protocol);
 
  template <class Proto>
  stdx::expected<void, std::error_code> discard_current_msg(
      TlsSwitchableConnection<Proto> &conn) {
    return discard_current_msg(conn.channel(), conn.protocol());
  }
 
  /**
   * log a message with error-code as error.
   */
  static void log_fatal_error_code(const char *msg, std::error_code ec);
 
  // see MysqlClassicConnection::trace()
  [[deprecated(
      "use 'if (auto &tr = tracer()) { tr.trace(...); } instead")]] void
  trace(Tracer::Event e);
 
  Tracer &tracer();
 
  /**
   * start a span.
   *
   * @param parent_span parent span to nest this trace span in.
   * @param prefix name of the span.
   */
  TraceEvent *trace_span(TraceEvent *parent_span,
                         const std::string_view &prefix);
 
  /**
   * end a span and set a status-code.
   */
  void trace_span_end(TraceEvent *event, TraceEvent::StatusCode status_code =
                                             TraceEvent::StatusCode::kUnset);
 
  /**
   * start a command span.
   *
   * @param prefix name of the command span.
   */
  TraceEvent *trace_command(const std::string_view &prefix);
 
  /**
   * start a connect-and-forward span.
   */
  TraceEvent *trace_connect_and_forward_command(TraceEvent *parent_span);
 
  /**
   * start a connect span.
   */
  TraceEvent *trace_connect(TraceEvent *parent_span);
 
  /**
   * start a connect span.
   */
  void trace_set_connection_attributes(TraceEvent *ev);
 
  /**
   * start a forward span.
   */
  TraceEvent *trace_forward_command(TraceEvent *parent_span);
 
  /**
   * end a command span and set a status-code.
   */
  void trace_command_end(TraceEvent *event, TraceEvent::StatusCode status_code =
                                                TraceEvent::StatusCode::kUnset);
};
 
#endif