classic_lazy_connect.h

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/*
  Copyright (c) 2022, 2024, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  as designated in a particular file or component or in included license
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  permission to link the program and your derivative works with the
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  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef ROUTING_CLASSIC_LAZY_CONNECT_INCLUDED
#define ROUTING_CLASSIC_LAZY_CONNECT_INCLUDED
 
#include <system_error>
 
#include "forwarding_processor.h"
#include "mysqlrouter/classic_protocol_message.h"
#include "router_require.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 ForwardingProcessor {
 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.
   * @param parent_event parent event for the tracer
   *
   * 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,
      TraceEvent *parent_event)
      : ForwardingProcessor(conn),
        in_handshake_{in_handshake},
        on_error_(std::move(on_error)),
        parent_event_(parent_event) {}
 
  enum class Stage {
    FromStash,
    Connect,
    Connected,
    Authenticated,
    FetchUserAttrs,
    FetchUserAttrsDone,
    SendAuthOk,
    SetVars,
    SetVarsDone,
    SetServerOption,
    SetServerOptionDone,
    SetSchema,
    SetSchemaDone,
    FetchSysVars,
    FetchSysVarsDone,
    WaitGtidExecuted,
    WaitGtidExecutedDone,
    SetTrxCharacteristics,
    SetTrxCharacteristicsDone,
 
    PoolOrClose,
    FallbackToWrite,
 
    Done,
  };
 
  stdx::expected<Processor::Result, std::error_code> process() override;
 
  void stage(Stage stage) { stage_ = stage; }
  [[nodiscard]] Stage stage() const { return stage_; }
 
  struct RequiredConnectionAttributes {
    std::optional<bool> ssl;
    std::optional<bool> x509;
    std::optional<std::string> issuer;
    std::optional<std::string> subject;
  };
 
  void failed(
      const std::optional<classic_protocol::message::server::Error> &err) {
    failed_ = err;
  }
 
  std::optional<classic_protocol::message::server::Error> failed() const {
    return failed_;
  }
 
 private:
  stdx::expected<Processor::Result, std::error_code> from_stash();
  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> fetch_user_attrs();
  stdx::expected<Processor::Result, std::error_code> fetch_user_attrs_done();
  stdx::expected<Processor::Result, std::error_code> send_auth_ok();
  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();
  stdx::expected<Processor::Result, std::error_code> wait_gtid_executed();
  stdx::expected<Processor::Result, std::error_code> wait_gtid_executed_done();
  stdx::expected<Processor::Result, std::error_code> set_trx_characteristics();
  stdx::expected<Processor::Result, std::error_code>
  set_trx_characteristics_done();
 
  stdx::expected<Processor::Result, std::error_code> pool_or_close();
  stdx::expected<Processor::Result, std::error_code> fallback_to_write();
 
  Stage stage_{Stage::FromStash};
 
  bool in_handshake_;
 
  RouterRequireFetcher::Result required_connection_attributes_fetcher_result_;
 
  std::function<void(const classic_protocol::message::server::Error &err)>
      on_error_;
 
  bool retry_connect_{false};     // set on transient failure
  bool already_fallback_{false};  // set in fallback_to_write()
 
  // start timepoint to calculate the connect-retry-timeout.
  std::chrono::steady_clock::time_point started_{
      std::chrono::steady_clock::now()};
 
  std::optional<classic_protocol::message::server::Error> failed_;
 
  std::string trx_stmt_;
 
  TraceEvent *parent_event_{};
  TraceEvent *trace_event_connect_{};
  TraceEvent *trace_event_authenticate_{};
  TraceEvent *trace_event_set_vars_{};
  TraceEvent *trace_event_fetch_sys_vars_{};
  TraceEvent *trace_event_set_schema_{};
  TraceEvent *trace_event_wait_gtid_executed_{};
  TraceEvent *trace_event_check_read_only_{};
  TraceEvent *trace_event_fallback_to_write_{};
  TraceEvent *trace_event_set_trx_characteristics_{};
};
 
#endif