syncrep.h

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/*-------------------------------------------------------------------------
 *
 * syncrep.h
 *    Exports from replication/syncrep.c.
 *
 * Portions Copyright (c) 2010-2021, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      src/include/replication/syncrep.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef _SYNCREP_H
#define _SYNCREP_H

#include "access/xlogdefs.h"
#include "utils/guc.h"

#define SyncRepRequested() \
    (max_wal_senders > 0 && synchronous_commit > SYNCHRONOUS_COMMIT_LOCAL_FLUSH)

/* SyncRepWaitMode */
#define SYNC_REP_NO_WAIT        (-1)
#define SYNC_REP_WAIT_WRITE     0
#define SYNC_REP_WAIT_FLUSH     1
#define SYNC_REP_WAIT_APPLY     2

#define NUM_SYNC_REP_WAIT_MODE  3

/* syncRepState */
#define SYNC_REP_NOT_WAITING        0
#define SYNC_REP_WAITING            1
#define SYNC_REP_WAIT_COMPLETE      2

/* syncrep_method of SyncRepConfigData */
#define SYNC_REP_PRIORITY       0
#define SYNC_REP_QUORUM     1

/*
 * SyncRepGetCandidateStandbys returns an array of these structs,
 * one per candidate synchronous walsender.
 */
typedef struct SyncRepStandbyData
{
    /* Copies of relevant fields from WalSnd shared-memory struct */
    pid_t       pid;
    XLogRecPtr  write;
    XLogRecPtr  flush;
    XLogRecPtr  apply;
    int         sync_standby_priority;
    /* Index of this walsender in the WalSnd shared-memory array */
    int         walsnd_index;
    /* This flag indicates whether this struct is about our own process */
    bool        is_me;
} SyncRepStandbyData;

/*
 * Struct for the configuration of synchronous replication.
 *
 * Note: this must be a flat representation that can be held in a single
 * chunk of malloc'd memory, so that it can be stored as the "extra" data
 * for the synchronous_standby_names GUC.
 */
typedef struct SyncRepConfigData
{
    int         config_size;    /* total size of this struct, in bytes */
    int         num_sync;       /* number of sync standbys that we need to
                                 * wait for */
    uint8       syncrep_method; /* method to choose sync standbys */
    int         nmembers;       /* number of members in the following list */
    /* member_names contains nmembers consecutive nul-terminated C strings */
    char        member_names[FLEXIBLE_ARRAY_MEMBER];
} SyncRepConfigData;

extern SyncRepConfigData *SyncRepConfig;

/* communication variables for parsing synchronous_standby_names GUC */
extern SyncRepConfigData *syncrep_parse_result;
extern char *syncrep_parse_error_msg;

/* user-settable parameters for synchronous replication */
extern char *SyncRepStandbyNames;

/* called by user backend */
extern void SyncRepWaitForLSN(XLogRecPtr lsn, bool commit);

/* called at backend exit */
extern void SyncRepCleanupAtProcExit(void);

/* called by wal sender */
extern void SyncRepInitConfig(void);
extern void SyncRepReleaseWaiters(void);

/* called by wal sender and user backend */
extern int  SyncRepGetCandidateStandbys(SyncRepStandbyData **standbys);

/* called by checkpointer */
extern void SyncRepUpdateSyncStandbysDefined(void);

/* GUC infrastructure */
extern bool check_synchronous_standby_names(char **newval, void **extra, GucSource source);
extern void assign_synchronous_standby_names(const char *newval, void *extra);
extern void assign_synchronous_commit(int newval, void *extra);

/*
 * Internal functions for parsing synchronous_standby_names grammar,
 * in syncrep_gram.y and syncrep_scanner.l
 */
extern int  syncrep_yyparse(void);
extern int  syncrep_yylex(void);
extern void syncrep_yyerror(const char *str);
extern void syncrep_scanner_init(const char *query_string);
extern void syncrep_scanner_finish(void);

#endif                          /* _SYNCREP_H */