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postgres/src/include/access/xlog.h
Tom Lane cba8fc6882 Make checkpoint requests more robust. 
Commit 6f6a6d8b1 introduced a delay of up to 2 seconds if we're trying
to request a checkpoint but the checkpointer hasn't started yet (or,
much less likely, our kill() call fails).  However buildfarm experience
shows that that's not quite enough for slow or heavily-loaded machines.
There's no good reason to assume that the checkpointer won't start
eventually, so we may as well make the timeout much longer, say 60 sec.

However, if the caller didn't say CHECKPOINT_WAIT, it seems like a bad
idea to be waiting at all, much less for as long as 60 sec.  We can
remove the need for that, and make this whole thing more robust, by
adjusting the code so that the existence of a pending checkpoint
request is clear from the contents of shared memory, and making sure
that the checkpointer process will notice it at startup even if it did
not get a signal.  In this way there's no need for a non-CHECKPOINT_WAIT
call to wait at all; if it can't send the signal, it can nonetheless
assume that the checkpointer will eventually service the request.

A potential downside of this change is that "kill -INT" on the checkpointer
process is no longer enough to trigger a checkpoint, should anyone be
relying on something so hacky.  But there's no obvious reason to do it
like that rather than issuing a plain old CHECKPOINT command, so we'll
assume that nobody is.  There doesn't seem to be a way to preserve this
undocumented quasi-feature without introducing race conditions.

Since a principal reason for messing with this is to prevent intermittent
buildfarm failures, back-patch to all supported branches.

Discussion: https://postgr.es/m/27830.1552752475@sss.pgh.pa.us
2019-03-19 12:49:27 -04:00

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/*
* xlog.h
*
* PostgreSQL write-ahead log manager
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/xlog.h
*/
#ifndef XLOG_H
#define XLOG_H
#include "access/rmgr.h"
#include "access/xlogdefs.h"
#include "access/xloginsert.h"
#include "access/xlogreader.h"
#include "datatype/timestamp.h"
#include "lib/stringinfo.h"
#include "nodes/pg_list.h"
#include "storage/fd.h"
/* Sync methods */
#define SYNC_METHOD_FSYNC 0
#define SYNC_METHOD_FDATASYNC 1
#define SYNC_METHOD_OPEN 2 /* for O_SYNC */
#define SYNC_METHOD_FSYNC_WRITETHROUGH 3
#define SYNC_METHOD_OPEN_DSYNC 4 /* for O_DSYNC */
extern int sync_method;
extern PGDLLIMPORT TimeLineID ThisTimeLineID; /* current TLI */
/*
* Prior to 8.4, all activity during recovery was carried out by the startup
* process. This local variable continues to be used in many parts of the
* code to indicate actions taken by RecoveryManagers. Other processes that
* potentially perform work during recovery should check RecoveryInProgress().
* See XLogCtl notes in xlog.c.
*/
extern bool InRecovery;
/*
* Like InRecovery, standbyState is only valid in the startup process.
* In all other processes it will have the value STANDBY_DISABLED (so
* InHotStandby will read as false).
*
* In DISABLED state, we're performing crash recovery or hot standby was
* disabled in postgresql.conf.
*
* In INITIALIZED state, we've run InitRecoveryTransactionEnvironment, but
* we haven't yet processed a RUNNING_XACTS or shutdown-checkpoint WAL record
* to initialize our master-transaction tracking system.
*
* When the transaction tracking is initialized, we enter the SNAPSHOT_PENDING
* state. The tracked information might still be incomplete, so we can't allow
* connections yet, but redo functions must update the in-memory state when
* appropriate.
*
* In SNAPSHOT_READY mode, we have full knowledge of transactions that are
* (or were) running in the master at the current WAL location. Snapshots
* can be taken, and read-only queries can be run.
*/
typedef enum
{
STANDBY_DISABLED,
STANDBY_INITIALIZED,
STANDBY_SNAPSHOT_PENDING,
STANDBY_SNAPSHOT_READY
} HotStandbyState;
extern HotStandbyState standbyState;
#define InHotStandby (standbyState >= STANDBY_SNAPSHOT_PENDING)
/*
* Recovery target type.
* Only set during a Point in Time recovery, not when standby_mode = on
*/
typedef enum
{
RECOVERY_TARGET_UNSET,
RECOVERY_TARGET_XID,
RECOVERY_TARGET_TIME,
RECOVERY_TARGET_NAME,
RECOVERY_TARGET_LSN,
RECOVERY_TARGET_IMMEDIATE
} RecoveryTargetType;
extern XLogRecPtr ProcLastRecPtr;
extern XLogRecPtr XactLastRecEnd;
extern PGDLLIMPORT XLogRecPtr XactLastCommitEnd;
extern bool reachedConsistency;
/* these variables are GUC parameters related to XLOG */
extern int wal_segment_size;
extern int min_wal_size_mb;
extern int max_wal_size_mb;
extern int wal_keep_segments;
extern int XLOGbuffers;
extern int XLogArchiveTimeout;
extern int wal_retrieve_retry_interval;
extern char *XLogArchiveCommand;
extern bool EnableHotStandby;
extern bool fullPageWrites;
extern bool wal_log_hints;
extern bool wal_compression;
extern bool *wal_consistency_checking;
extern char *wal_consistency_checking_string;
extern bool log_checkpoints;
extern int CheckPointSegments;
/* Archive modes */
typedef enum ArchiveMode
{
ARCHIVE_MODE_OFF = 0, /* disabled */
ARCHIVE_MODE_ON, /* enabled while server is running normally */
ARCHIVE_MODE_ALWAYS /* enabled always (even during recovery) */
} ArchiveMode;
extern int XLogArchiveMode;
/* WAL levels */
typedef enum WalLevel
{
WAL_LEVEL_MINIMAL = 0,
WAL_LEVEL_REPLICA,
WAL_LEVEL_LOGICAL
} WalLevel;
extern PGDLLIMPORT int wal_level;
/* Is WAL archiving enabled (always or only while server is running normally)? */
#define XLogArchivingActive() \
(AssertMacro(XLogArchiveMode == ARCHIVE_MODE_OFF || wal_level >= WAL_LEVEL_REPLICA), XLogArchiveMode > ARCHIVE_MODE_OFF)
/* Is WAL archiving enabled always (even during recovery)? */
#define XLogArchivingAlways() \
(AssertMacro(XLogArchiveMode == ARCHIVE_MODE_OFF || wal_level >= WAL_LEVEL_REPLICA), XLogArchiveMode == ARCHIVE_MODE_ALWAYS)
#define XLogArchiveCommandSet() (XLogArchiveCommand[0] != '\0')
/*
* Is WAL-logging necessary for archival or log-shipping, or can we skip
* WAL-logging if we fsync() the data before committing instead?
*/
#define XLogIsNeeded() (wal_level >= WAL_LEVEL_REPLICA)
/*
* Is a full-page image needed for hint bit updates?
*
* Normally, we don't WAL-log hint bit updates, but if checksums are enabled,
* we have to protect them against torn page writes. When you only set
* individual bits on a page, it's still consistent no matter what combination
* of the bits make it to disk, but the checksum wouldn't match. Also WAL-log
* them if forced by wal_log_hints=on.
*/
#define XLogHintBitIsNeeded() (DataChecksumsEnabled() || wal_log_hints)
/* Do we need to WAL-log information required only for Hot Standby and logical replication? */
#define XLogStandbyInfoActive() (wal_level >= WAL_LEVEL_REPLICA)
/* Do we need to WAL-log information required only for logical replication? */
#define XLogLogicalInfoActive() (wal_level >= WAL_LEVEL_LOGICAL)
#ifdef WAL_DEBUG
extern bool XLOG_DEBUG;
#endif
/*
* OR-able request flag bits for checkpoints. The "cause" bits are used only
* for logging purposes. Note: the flags must be defined so that it's
* sensible to OR together request flags arising from different requestors.
*/
/* These directly affect the behavior of CreateCheckPoint and subsidiaries */
#define CHECKPOINT_IS_SHUTDOWN 0x0001 /* Checkpoint is for shutdown */
#define CHECKPOINT_END_OF_RECOVERY 0x0002 /* Like shutdown checkpoint, but
* issued at end of WAL recovery */
#define CHECKPOINT_IMMEDIATE 0x0004 /* Do it without delays */
#define CHECKPOINT_FORCE 0x0008 /* Force even if no activity */
#define CHECKPOINT_FLUSH_ALL 0x0010 /* Flush all pages, including those
* belonging to unlogged tables */
/* These are important to RequestCheckpoint */
#define CHECKPOINT_WAIT 0x0020 /* Wait for completion */
/* These indicate the cause of a checkpoint request */
#define CHECKPOINT_CAUSE_XLOG 0x0040 /* XLOG consumption */
#define CHECKPOINT_CAUSE_TIME 0x0080 /* Elapsed time */
/* We set this to ensure that ckpt_flags is not 0 if a request has been made */
#define CHECKPOINT_REQUESTED 0x0100 /* Checkpoint request has been made */
/*
* Flag bits for the record being inserted, set using XLogSetRecordFlags().
*/
#define XLOG_INCLUDE_ORIGIN 0x01 /* include the replication origin */
#define XLOG_MARK_UNIMPORTANT 0x02 /* record not important for durability */
/* Checkpoint statistics */
typedef struct CheckpointStatsData
{
TimestampTz ckpt_start_t; /* start of checkpoint */
TimestampTz ckpt_write_t; /* start of flushing buffers */
TimestampTz ckpt_sync_t; /* start of fsyncs */
TimestampTz ckpt_sync_end_t; /* end of fsyncs */
TimestampTz ckpt_end_t; /* end of checkpoint */
int ckpt_bufs_written; /* # of buffers written */
int ckpt_segs_added; /* # of new xlog segments created */
int ckpt_segs_removed; /* # of xlog segments deleted */
int ckpt_segs_recycled; /* # of xlog segments recycled */
int ckpt_sync_rels; /* # of relations synced */
uint64 ckpt_longest_sync; /* Longest sync for one relation */
uint64 ckpt_agg_sync_time; /* The sum of all the individual sync
* times, which is not necessarily the
* same as the total elapsed time for the
* entire sync phase. */
} CheckpointStatsData;
extern CheckpointStatsData CheckpointStats;
struct XLogRecData;
extern XLogRecPtr XLogInsertRecord(struct XLogRecData *rdata,
XLogRecPtr fpw_lsn,
uint8 flags);
extern void XLogFlush(XLogRecPtr RecPtr);
extern bool XLogBackgroundFlush(void);
extern bool XLogNeedsFlush(XLogRecPtr RecPtr);
extern int XLogFileInit(XLogSegNo segno, bool *use_existent, bool use_lock);
extern int XLogFileOpen(XLogSegNo segno);
extern void CheckXLogRemoved(XLogSegNo segno, TimeLineID tli);
extern XLogSegNo XLogGetLastRemovedSegno(void);
extern void XLogSetAsyncXactLSN(XLogRecPtr record);
extern void XLogSetReplicationSlotMinimumLSN(XLogRecPtr lsn);
extern void xlog_redo(XLogReaderState *record);
extern void xlog_desc(StringInfo buf, XLogReaderState *record);
extern const char *xlog_identify(uint8 info);
extern void issue_xlog_fsync(int fd, XLogSegNo segno);
extern bool RecoveryInProgress(void);
extern bool HotStandbyActive(void);
extern bool HotStandbyActiveInReplay(void);
extern bool XLogInsertAllowed(void);
extern void GetXLogReceiptTime(TimestampTz *rtime, bool *fromStream);
extern XLogRecPtr GetXLogReplayRecPtr(TimeLineID *replayTLI);
extern XLogRecPtr GetXLogInsertRecPtr(void);
extern XLogRecPtr GetXLogWriteRecPtr(void);
extern bool RecoveryIsPaused(void);
extern void SetRecoveryPause(bool recoveryPause);
extern TimestampTz GetLatestXTime(void);
extern TimestampTz GetCurrentChunkReplayStartTime(void);
extern char *XLogFileNameP(TimeLineID tli, XLogSegNo segno);
extern void UpdateControlFile(void);
extern uint64 GetSystemIdentifier(void);
extern char *GetMockAuthenticationNonce(void);
extern bool DataChecksumsEnabled(void);
extern XLogRecPtr GetFakeLSNForUnloggedRel(void);
extern Size XLOGShmemSize(void);
extern void XLOGShmemInit(void);
extern void BootStrapXLOG(void);
extern void LocalProcessControlFile(bool reset);
extern void StartupXLOG(void);
extern void ShutdownXLOG(int code, Datum arg);
extern void InitXLOGAccess(void);
extern void CreateCheckPoint(int flags);
extern bool CreateRestartPoint(int flags);
extern void XLogPutNextOid(Oid nextOid);
extern XLogRecPtr XLogRestorePoint(const char *rpName);
extern void UpdateFullPageWrites(void);
extern void GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p);
extern XLogRecPtr GetRedoRecPtr(void);
extern XLogRecPtr GetInsertRecPtr(void);
extern XLogRecPtr GetFlushRecPtr(void);
extern XLogRecPtr GetLastImportantRecPtr(void);
extern void GetNextXidAndEpoch(TransactionId *xid, uint32 *epoch);
extern void RemovePromoteSignalFiles(void);
extern bool CheckPromoteSignal(void);
extern void WakeupRecovery(void);
extern void SetWalWriterSleeping(bool sleeping);
extern void XLogRequestWalReceiverReply(void);
extern void assign_max_wal_size(int newval, void *extra);
extern void assign_checkpoint_completion_target(double newval, void *extra);
/*
* Routines to start, stop, and get status of a base backup.
*/
/*
* Session-level status of base backups
*
* This is used in parallel with the shared memory status to control parallel
* execution of base backup functions for a given session, be it a backend
* dedicated to replication or a normal backend connected to a database. The
* update of the session-level status happens at the same time as the shared
* memory counters to keep a consistent global and local state of the backups
* running.
*/
typedef enum SessionBackupState
{
SESSION_BACKUP_NONE,
SESSION_BACKUP_EXCLUSIVE,
SESSION_BACKUP_NON_EXCLUSIVE
} SessionBackupState;
extern XLogRecPtr do_pg_start_backup(const char *backupidstr, bool fast,
TimeLineID *starttli_p, StringInfo labelfile,
List **tablespaces, StringInfo tblspcmapfile, bool infotbssize,
bool needtblspcmapfile);
extern XLogRecPtr do_pg_stop_backup(char *labelfile, bool waitforarchive,
TimeLineID *stoptli_p);
extern void do_pg_abort_backup(void);
extern SessionBackupState get_backup_status(void);
/* File path names (all relative to $PGDATA) */
#define BACKUP_LABEL_FILE "backup_label"
#define BACKUP_LABEL_OLD "backup_label.old"
#define TABLESPACE_MAP "tablespace_map"
#define TABLESPACE_MAP_OLD "tablespace_map.old"
#endif /* XLOG_H */
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