66e9be814b
------- Removed DCB states DCB_STATE_IDLE, and DCB_STATE_PROCESSING. Added DCB_STATE_UNDEFINED for initial content for state variable which doesn't have any specific value set, and DCB_STATE_NOPOLLING to indicate that dcb has been removed from poll set. Added following dcb roles: DCB_ROLE_SERVICE_LISTENER for listeners of services, and DCB_ROLE_REQUEST_HANDLER for client/backend dcbs. Listeners may have state DCB_STATE_LISTENING, but not DCB_STATE_POLLING. Request handlers may have DCB_STATE_POLLING but not DCB_STATE_LISTENING. Role is passed as an argument to dcb.c:dcb_alloc. From now on, struct check numbers of DCB are included and checked in DEBUG build only. Added dcb_role_t dcb_role-member to DCB as well as SPINLOCK dcb_initlock, which protects state changes. Removed extern keyword from function declarations because functions are by default externally visible if they are declared in header. dcb.b ------ Function dcb_set_state, and dcb_set_state_nomutex provide functions for changing dcb states. Latter implements a state machine for dcb. Function dcb_add_to_zombieslist replaces dcb_free. It adds in atomic step dcb to zombieslist and changes state to DCB_STATE_ZOMBIE. Function dcb_final_free removes dcb from allDCBs list, terminates router and client sessions, and frees dcb and related memory. Function dcb_process_zombies removes executing thread from dcb's bitmask, and it there are no further thread bits, moves dcb to a victim list, and finally, for each dcb on victim list, closes fd and sets state to DCB_STATE_DISCONNECTED. Function dcb_close sets dcb state to DCB_STATE_NOPOLLIN, removes dcb from poll set and sets bit to bitmask for each server thread in an atomic step. poll.c ------ Function poll_add_dcb sets either DCB_STATE_LISTENING or DCB_STATE_POLLING state for newly created dcb, depending whether the role of dcb is DCB_ROLE_SERVICE_LISTENER, or DCB_ROLE_REQUEST_HANDLER, respectively. Then dcb is set to poll set. poll_waitevents : commented out code which skipped event if dcb was added to zombieslist or if fd was closed. Added state checks. service.c : Minor changes. httpd.c : Removed dcb state changes. They are done in core. mysql_backend.c : Added checks, removed dcb state changes. mysql_client.c : Removed dcb state changes. Added checks. mysql_common.c : Minor changes telnetd.c : Removed state changes. Replaced some typecasts and pointer references with local variable reads. skygw_debug.h : Removed two states, and added two to state printing macro.
217 lines
8.5 KiB
C
217 lines
8.5 KiB
C
#ifndef _DCB_H
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#define _DCB_H
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/*
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* This file is distributed as part of the SkySQL Gateway. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright SkySQL Ab 2013
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*/
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#include <spinlock.h>
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#include <buffer.h>
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#include <gwbitmask.h>
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#include <skygw_utils.h>
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struct session;
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struct server;
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struct service;
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/**
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* @file dcb.h The Descriptor Control Block
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*
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* The function pointer table used by descriptors to call relevant functions
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* within the protocol specific code.
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 01/06/2013 Mark Riddoch Initial implementation
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* 11/06/2013 Mark Riddoch Updated GWPROTOCOL structure with new
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* entry points
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* 18/06/2013 Mark Riddoch Addition of the listener entry point
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* 02/07/2013 Massimiliano Pinto Addition of delayqlock, delayq and authlock
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* for handling backend asynchronous protocol connection
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* and a generic lock for backend authentication
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* 12/07/2013 Massimiliano Pinto Added auth entry point
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* 15/07/2013 Massimiliano Pinto Added session entry point
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* 16/07/2013 Massimiliano Pinto Added command type for dcb
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*
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* @endverbatim
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*/
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struct dcb;
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/**
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* @verbatim
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* The operations that can be performed on the descriptor
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*
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* read EPOLLIN handler for the socket
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* write Gateway data write entry point
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* write_ready EPOLLOUT handler for the socket, indicates
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* that the socket is ready to send more data
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* error EPOLLERR handler for the socket
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* hangup EPOLLHUP handler for the socket
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* accept Accept handler for listener socket only
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* connect Create a connection to the specified server
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* for the session pased in
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* close Gateway close entry point for the socket
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* listen Create a listener for the protocol
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* auth Authentication entry point
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* session Session handling entry point
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* @endverbatim
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*
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* This forms the "module object" for protocol modules within the gateway.
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*
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* @see load_module
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*/
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typedef struct gw_protocol {
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int (*read)(struct dcb *);
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int (*write)(struct dcb *, GWBUF *);
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int (*write_ready)(struct dcb *);
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int (*error)(struct dcb *);
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int (*hangup)(struct dcb *);
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int (*accept)(struct dcb *);
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int (*connect)(struct dcb *, struct server *, struct session *);
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int (*close)(struct dcb *);
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int (*listen)(struct dcb *, char *);
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int (*auth)(struct dcb *, struct server *, struct session *, GWBUF *);
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int (*session)(struct dcb *, void *);
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} GWPROTOCOL;
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/**
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* The statitics gathered on a descriptor control block
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*/
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typedef struct dcbstats {
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int n_reads; /**< Number of reads on this descriptor */
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int n_writes; /**< Number of writes on this descriptor */
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int n_accepts; /**< Number of accepts on this descriptor */
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int n_buffered; /**< Number of buffered writes */
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} DCBSTATS;
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/**
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* The data structure that is embedded witin a DCB and manages the complex memory
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* management issues of a DCB.
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*
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* The DCB structures are used as the user data within the polling loop. This means that
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* polling threads may aschronously wake up and access these structures. It is not possible
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* to simple remove the DCB from the epoll system and then free the data, as every thread
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* that is currently running an epoll call must wake up and re-issue the epoll_wait system
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* call, the is the only way we can be sure that no polling thread is pending a wakeup or
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* processing an event that will access the DCB.
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*
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* We solve this issue by making the dcb_free routine merely mark a DCB as a zombie and
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* place it on a special zombie list. Before placing the DCB on the zombie list we create
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* a bitmask with a bit set in it for each active polling thread. Each thread will call
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* a routine to process the zombie list at the end of the polling loop. This routine
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* will clear the bit value that corresponds to the calling thread. Once the bitmask
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* is completely cleared the DCB can finally be freed and removed from the zombie list.
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*/
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typedef struct {
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GWBITMASK bitmask; /**< The bitmask of threads */
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struct dcb *next; /**< Next pointer for the zombie list */
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} DCBMM;
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/* DCB states */
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typedef enum {
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DCB_STATE_UNDEFINED, /**< State variable with no state */
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DCB_STATE_ALLOC, /**< Memory allocated but not populated */
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DCB_STATE_POLLING, /**< Waiting in the poll loop */
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DCB_STATE_LISTENING, /**< The DCB is for a listening socket */
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DCB_STATE_DISCONNECTED, /**< The socket is now closed */
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DCB_STATE_FREED, /**< Memory freed */
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DCB_STATE_NOPOLLING, /**< Removed from poll mask */
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DCB_STATE_ZOMBIE /**< DCB is no longer active, waiting to free it */
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} dcb_state_t;
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typedef enum {
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DCB_ROLE_SERVICE_LISTENER,
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DCB_ROLE_REQUEST_HANDLER
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} dcb_role_t;
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/**
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* Descriptor Control Block
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*
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* A wrapper for a network descriptor within the gateway, it contains all the
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* state information necessary to allow for the implementation of the asynchronous
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* operation of the potocol and gateway functions. It also provides links to the service
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* and session data that is required to route the information within the gateway.
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*
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* It is important to hold the state information here such that any thread within the
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* gateway may be selected to execute the required actions when a network event occurs.
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*/
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typedef struct dcb {
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#if defined(SS_DEBUG)
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skygw_chk_t dcb_chk_top;
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#endif
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dcb_role_t dcb_role;
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SPINLOCK dcb_initlock;
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simple_mutex_t dcb_read_lock;
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simple_mutex_t dcb_write_lock;
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int fd; /**< The descriptor */
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bool dcb_read_active;
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bool dcb_write_active;
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dcb_state_t state; /**< Current descriptor state */
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char *remote; /**< Address of remote end */
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void *protocol; /**< The protocol specific state */
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struct session *session; /**< The owning session */
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GWPROTOCOL func; /**< The functions for this descriptor */
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SPINLOCK writeqlock; /**< Write Queue spinlock */
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GWBUF *writeq; /**< Write Data Queue */
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SPINLOCK delayqlock; /**< Delay Backend Write Queue spinlock */
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GWBUF *delayq; /**< Delay Backend Write Data Queue */
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SPINLOCK authlock; /**< Generic Authorization spinlock */
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DCBSTATS stats; /**< DCB related statistics */
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struct dcb *next; /**< Next DCB in the chain of allocated DCB's */
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struct service *service; /**< The related service */
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void *data; /**< Specific client data */
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DCBMM memdata; /**< The data related to DCB memory management */
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int command; /**< Specific client command type */
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#if defined(SS_DEBUG)
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skygw_chk_t dcb_chk_tail;
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#endif
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} DCB;
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/* A few useful macros */
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#define DCB_SESSION(x) (x)->session
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#define DCB_PROTOCOL(x, type) (type *)((x)->protocol)
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#define DCB_ISZOMBIE(x) ((x)->state == DCB_STATE_ZOMBIE)
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DCB *dcb_alloc(dcb_role_t);
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void dcb_free(DCB *); /* Free a DCB */
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DCB *dcb_connect(struct server *, struct session *, const char *); /* prepare Backend connection */
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int dcb_read(DCB *, GWBUF **); /* Generic read routine */
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int dcb_write(DCB *, GWBUF *); /* Generic write routine */
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int dcb_drain_writeq(DCB *); /* Generic write routine */
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void dcb_close(DCB *); /* Generic close functionality */
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void dcb_process_zombies(int); /* Process Zombies */
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void printAllDCBs(); /* Debug to print all DCB in the system */
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void printDCB(DCB *); /* Debug print routine */
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void dprintAllDCBs(DCB *); /* Debug to print all DCB in the system */
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void dprintDCB(DCB *, DCB *); /* Debug to print a DCB in the system */
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const char *gw_dcb_state2string(int); /* DCB state to string */
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void dcb_printf(DCB *, const char *, ...); /* DCB version of printf */
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int dcb_isclient(DCB *); /* the DCB is the client of the session */
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void dcb_hashtable_stats(DCB *, void *); /**< Print statisitics */
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void dcb_add_to_zombieslist(DCB* dcb);
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bool dcb_set_state(
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DCB* dcb,
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dcb_state_t new_state,
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dcb_state_t* old_state);
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#endif /* _DCB_H */
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