#ifndef _DCB_H #define _DCB_H /* * This file is distributed as part of the SkySQL Gateway. It is free * software: you can redistribute it and/or modify it under the terms of the * GNU General Public License as published by the Free Software Foundation, * version 2. * * 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 along with * this program; if not, write to the Free Software Foundation, Inc., 51 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * * Copyright SkySQL Ab 2013 */ #include #include #include #include struct session; struct server; struct service; /** * @file dcb.h The Descriptor Control Block * * The function pointer table used by descriptors to call relevant functions * within the protocol specific code. * * @verbatim * Revision History * * Date Who Description * 01/06/2013 Mark Riddoch Initial implementation * 11/06/2013 Mark Riddoch Updated GWPROTOCOL structure with new * entry points * 18/06/2013 Mark Riddoch Addition of the listener entry point * 02/07/2013 Massimiliano Pinto Addition of delayqlock, delayq and authlock * for handling backend asynchronous protocol connection * and a generic lock for backend authentication * 12/07/2013 Massimiliano Pinto Added auth entry point * 15/07/2013 Massimiliano Pinto Added session entry point * 16/07/2013 Massimiliano Pinto Added command type for dcb * * @endverbatim */ struct dcb; /** * @verbatim * The operations that can be performed on the descriptor * * read EPOLLIN handler for the socket * write Gateway data write entry point * write_ready EPOLLOUT handler for the socket, indicates * that the socket is ready to send more data * error EPOLLERR handler for the socket * hangup EPOLLHUP handler for the socket * accept Accept handler for listener socket only * connect Create a connection to the specified server * for the session pased in * close Gateway close entry point for the socket * listen Create a listener for the protocol * auth Authentication entry point * session Session handling entry point * @endverbatim * * This forms the "module object" for protocol modules within the gateway. * * @see load_module */ typedef struct gw_protocol { int (*read)(struct dcb *); int (*write)(struct dcb *, GWBUF *); int (*write_ready)(struct dcb *); int (*error)(struct dcb *); int (*hangup)(struct dcb *); int (*accept)(struct dcb *); int (*connect)(struct dcb *, struct server *, struct session *); int (*close)(struct dcb *); int (*listen)(struct dcb *, char *); int (*auth)(struct dcb *, struct server *, struct session *, GWBUF *); int (*session)(struct dcb *, void *); } GWPROTOCOL; /** * The statitics gathered on a descriptor control block */ typedef struct dcbstats { int n_reads; /*< Number of reads on this descriptor */ int n_writes; /*< Number of writes on this descriptor */ int n_accepts; /*< Number of accepts on this descriptor */ int n_buffered; /*< Number of buffered writes */ } DCBSTATS; /** * The data structure that is embedded witin a DCB and manages the complex memory * management issues of a DCB. * * The DCB structures are used as the user data within the polling loop. This means that * polling threads may aschronously wake up and access these structures. It is not possible * to simple remove the DCB from the epoll system and then free the data, as every thread * that is currently running an epoll call must wake up and re-issue the epoll_wait system * call, the is the only way we can be sure that no polling thread is pending a wakeup or * processing an event that will access the DCB. * * We solve this issue by making the dcb_free routine merely mark a DCB as a zombie and * place it on a special zombie list. Before placing the DCB on the zombie list we create * a bitmask with a bit set in it for each active polling thread. Each thread will call * a routine to process the zombie list at the end of the polling loop. This routine * will clear the bit value that corresponds to the calling thread. Once the bitmask * is completely cleared the DCB can finally be freed and removed from the zombie list. */ typedef struct { GWBITMASK bitmask; /*< The bitmask of threads */ struct dcb *next; /*< Next pointer for the zombie list */ } DCBMM; /* DCB states */ typedef enum { DCB_STATE_UNDEFINED, /*< State variable with no state */ DCB_STATE_ALLOC, /*< Memory allocated but not populated */ DCB_STATE_POLLING, /*< Waiting in the poll loop */ DCB_STATE_LISTENING, /*< The DCB is for a listening socket */ DCB_STATE_DISCONNECTED, /*< The socket is now closed */ DCB_STATE_FREED, /*< Memory freed */ DCB_STATE_NOPOLLING, /*< Removed from poll mask */ DCB_STATE_ZOMBIE /*< DCB is no longer active, waiting to free it */ } dcb_state_t; typedef enum { DCB_ROLE_SERVICE_LISTENER, /*< Receives initial connect requests from clients */ DCB_ROLE_REQUEST_HANDLER /*< Serves dedicated client */ } dcb_role_t; /** * Descriptor Control Block * * A wrapper for a network descriptor within the gateway, it contains all the * state information necessary to allow for the implementation of the asynchronous * operation of the potocol and gateway functions. It also provides links to the service * and session data that is required to route the information within the gateway. * * It is important to hold the state information here such that any thread within the * gateway may be selected to execute the required actions when a network event occurs. */ typedef struct dcb { #if defined(SS_DEBUG) skygw_chk_t dcb_chk_top; #endif dcb_role_t dcb_role; SPINLOCK dcb_initlock; #if 1 simple_mutex_t dcb_read_lock; simple_mutex_t dcb_write_lock; bool dcb_read_active; bool dcb_write_active; #endif int fd; /**< The descriptor */ dcb_state_t state; /**< Current descriptor state */ char *remote; /**< Address of remote end */ void *protocol; /**< The protocol specific state */ struct session *session; /**< The owning session */ GWPROTOCOL func; /**< The functions for this descriptor */ SPINLOCK writeqlock; /**< Write Queue spinlock */ GWBUF *writeq; /**< Write Data Queue */ SPINLOCK delayqlock; /**< Delay Backend Write Queue spinlock */ GWBUF *delayq; /**< Delay Backend Write Data Queue */ SPINLOCK authlock; /**< Generic Authorization spinlock */ DCBSTATS stats; /**< DCB related statistics */ struct dcb *next; /**< Next DCB in the chain of allocated DCB's */ struct service *service; /**< The related service */ void *data; /**< Specific client data */ DCBMM memdata; /**< The data related to DCB memory management */ int command; /**< Specific client command type */ #if defined(SS_DEBUG) skygw_chk_t dcb_chk_tail; #endif } DCB; #if defined(SS_DEBUG) unsigned char dcb_fake_write_errno[10240]; __int32_t dcb_fake_write_ev[10240]; bool fail_next_backend_fd; bool fail_next_client_fd; int fail_next_accept; int fail_accept_errno; #endif /* A few useful macros */ #define DCB_SESSION(x) (x)->session #define DCB_PROTOCOL(x, type) (type *)((x)->protocol) #define DCB_ISZOMBIE(x) ((x)->state == DCB_STATE_ZOMBIE) DCB *dcb_get_zombies(void); int gw_write(int fd, const void* buf, size_t nbytes); int dcb_write(DCB *, GWBUF *); DCB *dcb_alloc(dcb_role_t); void dcb_free(DCB *); DCB *dcb_connect(struct server *, struct session *, const char *); int dcb_read(DCB *, GWBUF **); int dcb_drain_writeq(DCB *); void dcb_close(DCB *); DCB *dcb_process_zombies(int); /* Process Zombies */ void printAllDCBs(); /* Debug to print all DCB in the system */ void printDCB(DCB *); /* Debug print routine */ void dprintAllDCBs(DCB *); /* Debug to print all DCB in the system */ void dprintDCB(DCB *, DCB *); /* Debug to print a DCB in the system */ const char *gw_dcb_state2string(int); /* DCB state to string */ void dcb_printf(DCB *, const char *, ...); /* DCB version of printf */ int dcb_isclient(DCB *); /* the DCB is the client of the session */ void dcb_hashtable_stats(DCB *, void *); /**< Print statisitics */ void dcb_add_to_zombieslist(DCB* dcb); bool dcb_set_state( DCB* dcb, dcb_state_t new_state, dcb_state_t* old_state); #endif /* _DCB_H */