walsender_private.h

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/*-------------------------------------------------------------------------
 *
 * walsender_private.h
 *    Private definitions from replication/walsender.c.
 *
 * Portions Copyright (c) 2010-2025, PostgreSQL Global Development Group
 *
 * src/include/replication/walsender_private.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef _WALSENDER_PRIVATE_H
#define _WALSENDER_PRIVATE_H
 
#include "access/xlog.h"
#include "lib/ilist.h"
#include "nodes/nodes.h"
#include "nodes/replnodes.h"
#include "replication/syncrep.h"
#include "storage/condition_variable.h"
#include "storage/shmem.h"
#include "storage/spin.h"
 
typedef enum WalSndState
{
    WALSNDSTATE_STARTUP = 0,
    WALSNDSTATE_BACKUP,
    WALSNDSTATE_CATCHUP,
    WALSNDSTATE_STREAMING,
    WALSNDSTATE_STOPPING,
} WalSndState;
 
/*
 * Each walsender has a WalSnd struct in shared memory.
 *
 * This struct is protected by its 'mutex' spinlock field, except that some
 * members are only written by the walsender process itself, and thus that
 * process is free to read those members without holding spinlock.  pid and
 * needreload always require the spinlock to be held for all accesses.
 */
typedef struct WalSnd
{
    pid_t       pid;            /* this walsender's PID, or 0 if not active */
 
    WalSndState state;          /* this walsender's state */
    XLogRecPtr  sentPtr;        /* WAL has been sent up to this point */
    bool        needreload;     /* does currently-open file need to be
                                 * reloaded? */
 
    /*
     * The xlog locations that have been written, flushed, and applied by
     * standby-side. These may be invalid if the standby-side has not offered
     * values yet.
     */
    XLogRecPtr  write;
    XLogRecPtr  flush;
    XLogRecPtr  apply;
 
    /* Measured lag times, or -1 for unknown/none. */
    TimeOffset  writeLag;
    TimeOffset  flushLag;
    TimeOffset  applyLag;
 
    /*
     * The priority order of the standby managed by this WALSender, as listed
     * in synchronous_standby_names, or 0 if not-listed.
     */
    int         sync_standby_priority;
 
    /* Protects shared variables in this structure. */
    slock_t     mutex;
 
    /*
     * Timestamp of the last message received from standby.
     */
    TimestampTz replyTime;
 
    ReplicationKind kind;
} WalSnd;
 
extern PGDLLIMPORT WalSnd *MyWalSnd;
 
/* There is one WalSndCtl struct for the whole database cluster */
typedef struct
{
    /*
     * Synchronous replication queue with one queue per request type.
     * Protected by SyncRepLock.
     */
    dlist_head  SyncRepQueue[NUM_SYNC_REP_WAIT_MODE];
 
    /*
     * Current location of the head of the queue. All waiters should have a
     * waitLSN that follows this value. Protected by SyncRepLock.
     */
    XLogRecPtr  lsn[NUM_SYNC_REP_WAIT_MODE];
 
    /*
     * Status of data related to the synchronous standbys.  Waiting backends
     * can't reload the config file safely, so checkpointer updates this value
     * as needed. Protected by SyncRepLock.
     */
    bits8       sync_standbys_status;
 
    /* used as a registry of physical / logical walsenders to wake */
    ConditionVariable wal_flush_cv;
    ConditionVariable wal_replay_cv;
 
    /*
     * Used by physical walsenders holding slots specified in
     * synchronized_standby_slots to wake up logical walsenders holding
     * logical failover slots when a walreceiver confirms the receipt of LSN.
     */
    ConditionVariable wal_confirm_rcv_cv;
 
    WalSnd      walsnds[FLEXIBLE_ARRAY_MEMBER];
} WalSndCtlData;
 
/* Flags for WalSndCtlData->sync_standbys_status */
 
/*
 * Is the synchronous standby data initialized from the GUC?  This is set the
 * first time synchronous_standby_names is processed by the checkpointer.
 */
#define SYNC_STANDBY_INIT           (1 << 0)
 
/*
 * Is the synchronous standby data defined?  This is set when
 * synchronous_standby_names has some data, after being processed by the
 * checkpointer.
 */
#define SYNC_STANDBY_DEFINED        (1 << 1)
 
extern PGDLLIMPORT WalSndCtlData *WalSndCtl;
 
 
extern void WalSndSetState(WalSndState state);
 
/*
 * Internal functions for parsing the replication grammar, in repl_gram.y and
 * repl_scanner.l
 */
union YYSTYPE;
#ifndef YY_TYPEDEF_YY_SCANNER_T
#define YY_TYPEDEF_YY_SCANNER_T
typedef void *yyscan_t;
#endif
extern int  replication_yyparse(Node **replication_parse_result_p, yyscan_t yyscanner);
extern int  replication_yylex(union YYSTYPE *yylval_param, yyscan_t yyscanner);
pg_noreturn extern void replication_yyerror(Node **replication_parse_result_p, yyscan_t yyscanner, const char *message);
extern void replication_scanner_init(const char *str, yyscan_t *yyscannerp);
extern void replication_scanner_finish(yyscan_t yyscanner);
extern bool replication_scanner_is_replication_command(yyscan_t yyscanner);
 
#endif                          /* _WALSENDER_PRIVATE_H */