classic_lazy_connect.h

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*/
 
#ifndef ROUTING_CLASSIC_LAZY_CONNECT_INCLUDED
#define ROUTING_CLASSIC_LAZY_CONNECT_INCLUDED
 
#include <system_error>
 
#include "processor.h"
 
/**
 * attach a server connection and initialize it.
 *
 * - if a server-connection is attached to the client connection, leave.
 * - otherwise,
 *   - if a connection can be taken from the pool, take it.
 *   - otherwise, connect to the server and authenticate.
 * - set tracking session-vars
 * - set the client's schema, if it differs from the server-connection's.
 *
 * Precondition:
 *
 * - the client's cleartext password must be known.
 */
class LazyConnector : public Processor {
 public:
  /**
   * create a lazy-connector.
   *
   * @param conn a connection handle
   * @param in_handshake if true, the client connection is in Greeting or
   * ChangeUser right now.
   * @param on_error function that's called if an error happened.
   *
   * If "in_handshake" the LazyConnector may ask the client for a
   * "auth-method-switch" or a "plaintext-password".
   */
  LazyConnector(
      MysqlRoutingClassicConnectionBase *conn, bool in_handshake,
      std::function<void(const classic_protocol::message::server::Error &err)>
          on_error)
      : Processor(conn),
        in_handshake_{in_handshake},
        on_error_(std::move(on_error)) {}
 
  enum class Stage {
    Connect,
    Connected,
    Authenticated,
    SetVars,
    SetVarsDone,
    SetServerOption,
    SetServerOptionDone,
    SetSchema,
    SetSchemaDone,
    FetchSysVars,
    FetchSysVarsDone,
 
    Done,
  };
 
  stdx::expected<Processor::Result, std::error_code> process() override;
 
  void stage(Stage stage) { stage_ = stage; }
  [[nodiscard]] Stage stage() const { return stage_; }
 
 private:
  stdx::expected<Processor::Result, std::error_code> connect();
  stdx::expected<Processor::Result, std::error_code> connected();
  stdx::expected<Processor::Result, std::error_code> authenticated();
  stdx::expected<Processor::Result, std::error_code> set_vars();
  stdx::expected<Processor::Result, std::error_code> set_vars_done();
  stdx::expected<Processor::Result, std::error_code> set_server_option();
  stdx::expected<Processor::Result, std::error_code> set_server_option_done();
  stdx::expected<Processor::Result, std::error_code> set_schema();
  stdx::expected<Processor::Result, std::error_code> set_schema_done();
  stdx::expected<Processor::Result, std::error_code> fetch_sys_vars();
  stdx::expected<Processor::Result, std::error_code> fetch_sys_vars_done();
 
  Stage stage_{Stage::Connect};
 
  bool in_handshake_;
 
  std::function<void(const classic_protocol::message::server::Error &err)>
      on_error_;
};
 
#endif