376 lines
9.4 KiB
C++
376 lines
9.4 KiB
C++
/*
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* Copyright (c) 2018 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2022-01-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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#pragma once
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#include <maxscale/ccdefs.hh>
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#include <list>
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#include <string>
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#include <memory>
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#include <maxscale/service.hh>
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#include <maxscale/session_command.hh>
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#include <maxbase/stopwatch.hh>
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namespace maxscale
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{
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class Backend
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{
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Backend(const Backend&);
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Backend& operator=(const Backend&);
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public:
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/**
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* How is the backend being closed
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*/
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enum close_type
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{
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CLOSE_NORMAL,
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CLOSE_FATAL
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};
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/**
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* What type of a response we expect from the backend
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*/
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enum response_type
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{
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EXPECT_RESPONSE,
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NO_RESPONSE
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};
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/**
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* @brief Create new Backend
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*
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* @param ref Server reference used by this backend
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*/
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Backend(SERVER_REF* ref);
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virtual ~Backend();
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/**
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* @brief Execute the next session command in the queue
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*
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* @return True if the command was executed successfully
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*/
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virtual bool execute_session_command();
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/**
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* @brief Add a new session command to the tail of the command queue
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*
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* @param buffer Session command to add
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* @param sequence Sequence identifier of this session command, returned when
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* the session command is completed
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*/
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void append_session_command(GWBUF* buffer, uint64_t sequence);
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void append_session_command(const SSessionCommand& sescmd);
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void append_session_command(const SessionCommandList& sescmdlist);
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/**
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* @brief Mark the current session command as successfully executed
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*
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* This should be called when the response to the command is received
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*
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* @return The sequence identifier for this session command
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*/
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uint64_t complete_session_command();
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/**
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* @brief Get number of session commands
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*
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* @return Number of session commands
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*/
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size_t session_command_count() const;
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/**
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* @brief Check if there are session commands waiting to be executed
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*
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* @return True if there are session commands waiting to be executed
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*/
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inline bool has_session_commands() const
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{
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mxb_assert(in_use());
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return !m_session_commands.empty();
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}
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/**
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* @brief Get the first session command
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*
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* Returns the first session command in the list of session commands
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* to be executed.
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*
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* This should only be called when at least one session command has been
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* added to the backend. If no session commands have been added, behavior
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* is undefined.
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*
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* @return The first session command
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*/
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const SSessionCommand& next_session_command() const;
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/**
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* @brief Get pointer to server reference
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*
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* @return Pointer to server reference
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*/
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inline SERVER_REF* backend() const
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{
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mxb_assert(m_backend);
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return m_backend;
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}
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/**
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* @brief Get pointer to server
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*
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* @return Pointer to server
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*/
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inline SERVER* server() const
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{
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mxb_assert(m_backend);
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return m_backend->server;
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}
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/**
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* @brief Check if a connection to this backend can be made
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*
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* @return True if the backend has not failed and a connection can be attempted
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*/
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inline bool can_connect() const
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{
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return !has_failed() && server_is_usable(m_backend->server);
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}
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/**
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* @brief Create a new connection
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*
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* @param session The session to which the connection is linked
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* @param sescmd Pointer to a list of session commands to execute
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*
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* @return True if connection was successfully created
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*/
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bool connect(MXS_SESSION* session, SessionCommandList* sescmd = NULL);
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/**
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* @brief Close the backend
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*
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* This will close all active connections created by the backend.
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*/
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virtual void close(close_type type = CLOSE_NORMAL);
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/**
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* @brief Get a pointer to the internal DCB
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*
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* @return Pointer to DCB or NULL if not connected
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*/
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inline DCB* dcb() const
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{
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return m_dcb;
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}
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/**
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* @brief Write data to the backend server
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*
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* @param buffer Buffer containing the data to write
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* @param expect_response Whether to expect a response to the query
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*
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* @return True if data was written successfully
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*/
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virtual bool write(GWBUF* buffer, response_type type = EXPECT_RESPONSE);
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/**
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* @brief Write an authentication switch request to the backend server
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*
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* @param buffer Buffer containing the authentication switch request
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*
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* @return True if request was successfully written
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*/
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bool auth(GWBUF* buffer);
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/**
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* @brief Mark that a reply to a query was received and processed
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*/
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void ack_write();
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/**
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* @brief Store a command
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*
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* The command is stored and executed once the session can execute
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* the next command.
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*
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* @param buffer Buffer to store
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*/
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void store_command(GWBUF* buffer);
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/**
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* @brief Write the stored command to the backend server
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*
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* @return True if command was written successfully
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*/
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bool write_stored_command();
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/**
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* @brief Check if backend is in use
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*
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* @return True if backend is in use
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*/
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inline bool in_use() const
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{
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return m_state & IN_USE;
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}
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/**
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* @brief Check if the backend server reference is active
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*
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* @return True if the server reference is active
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*/
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inline bool is_active() const
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{
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return SERVER_REF_IS_ACTIVE(m_backend);
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}
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/**
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* @brief Check if backend is waiting for a result
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*
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* @return True if backend is waiting for a result
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*/
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inline bool is_waiting_result() const
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{
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return m_state & WAITING_RESULT;
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}
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/**
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* @brief Check if the backend is closed
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*
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* @return True if the backend is closed
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*/
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inline bool is_closed() const
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{
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return m_closed;
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}
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/**
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* @brief Check if the server is a master
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*
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* @return True if server is a master
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*/
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inline bool is_master() const
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{
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return server_is_master(m_backend->server);
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}
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/**
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* @brief Check if the server is a slave
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*
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* @return True if the server is a slave
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*/
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inline bool is_slave() const
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{
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return server_is_slave(m_backend->server);
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}
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/**
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* @brief Check if the server is a relay server
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*
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* @return True if the server is a relay server
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*/
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inline bool is_relay() const
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{
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return server_is_relay(m_backend->server);
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}
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/**
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* @brief Check if the backend has failed fatally
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*
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* When a fatal failure occurs in a backend, the backend server can no longer
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* be used by this session. Fatal failures can occur when the execution of
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* a session command fails on the backend but the expected result is different.
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*
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* @return True if a fatal failure has occurred in the backend server
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*/
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inline bool has_failed() const
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{
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return m_state & FATAL_FAILURE;
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}
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/**
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* @brief Get the object name of this server
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*
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* @return The unique object name of this server
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*/
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inline const char* name() const
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{
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return m_backend->server->name;
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}
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/**
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* @brief Get the address and port as a string
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*
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* @return The address and port combined into one string
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*/
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inline const char* uri() const
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{
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return m_uri.c_str();
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}
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void select_started();
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void select_ended();
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int64_t num_selects() const;
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const maxbase::StopWatch& session_timer() const;
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const maxbase::IntervalTimer& select_timer() const;
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private:
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/**
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* Internal state of the backend
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*/
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enum backend_state
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{
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IN_USE = 0x01, /**< Backend has been taken into use */
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WAITING_RESULT = 0x02, /**< Waiting for a reply */
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FATAL_FAILURE = 0x04 /**< Backend references that should be dropped */
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};
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/**
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* @brief Clear state
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*
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* @param state State to clear
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*/
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void clear_state(backend_state state);
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/**
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* @brief Set state
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*
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* @param state State to set
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*/
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void set_state(backend_state state);
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bool m_closed; /**< True if a connection has been opened and closed */
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SERVER_REF* m_backend; /**< Backend server */
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DCB* m_dcb; /**< Backend DCB */
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mxs::Buffer m_pending_cmd; /**< Pending commands */
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int m_state; /**< State of the backend */
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SessionCommandList m_session_commands; /**< List of session commands that are
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* to be executed on this backend server */
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std::string m_uri; /**< The combined address and port */
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maxbase::StopWatch m_session_timer;
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maxbase::IntervalTimer m_select_timer;
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int64_t m_num_selects = 0;
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};
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typedef std::shared_ptr<Backend> SBackend;
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typedef std::list<SBackend> BackendList;
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}
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