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479 lines
12 KiB
C
479 lines
12 KiB
C
/*-------------------------------------------------------------------------
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*
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* timeline.c
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* Functions for reading and writing timeline history files.
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*
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* A timeline history file lists the timeline changes of the timeline, in
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* a simple text format. They are archived along with the WAL segments.
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*
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* The files are named like "<tli>.history". For example, if the database
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* starts up and switches to timeline 5, the timeline history file would be
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* called "00000005.history".
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*
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* Each line in the file represents a timeline switch:
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*
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* <parentTLI> <switchpoint> <reason>
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*
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* parentTLI ID of the parent timeline
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* switchpoint XLogRecPtr of the WAL position where the switch happened
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* reason human-readable explanation of why the timeline was changed
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*
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* The fields are separated by tabs. Lines beginning with # are comments, and
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* are ignored. Empty lines are also ignored.
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*
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* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/backend/access/transam/timeline.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <sys/stat.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "access/timeline.h"
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#include "access/xlog_internal.h"
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#include "access/xlogdefs.h"
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#include "storage/fd.h"
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/*
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* Try to read a timeline's history file.
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*
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* If successful, return the list of component TLIs (the given TLI followed by
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* its ancestor TLIs). If we can't find the history file, assume that the
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* timeline has no parents, and return a list of just the specified timeline
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* ID.
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*/
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List *
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readTimeLineHistory(TimeLineID targetTLI)
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{
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List *result;
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char path[MAXPGPATH];
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char histfname[MAXFNAMELEN];
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char fline[MAXPGPATH];
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FILE *fd;
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TimeLineHistoryEntry *entry;
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TimeLineID lasttli = 0;
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XLogRecPtr prevend;
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/* Timeline 1 does not have a history file, so no need to check */
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if (targetTLI == 1)
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{
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entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
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entry->tli = targetTLI;
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entry->begin = entry->end = InvalidXLogRecPtr;
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return list_make1(entry);
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}
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if (InArchiveRecovery)
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{
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TLHistoryFileName(histfname, targetTLI);
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RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0, false);
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}
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else
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TLHistoryFilePath(path, targetTLI);
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fd = AllocateFile(path, "r");
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if (fd == NULL)
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{
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if (errno != ENOENT)
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ereport(FATAL,
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(errcode_for_file_access(),
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errmsg("could not open file \"%s\": %m", path)));
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/* Not there, so assume no parents */
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entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
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entry->tli = targetTLI;
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entry->begin = entry->end = InvalidXLogRecPtr;
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return list_make1(entry);
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}
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result = NIL;
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/*
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* Parse the file...
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*/
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prevend = InvalidXLogRecPtr;
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while (fgets(fline, sizeof(fline), fd) != NULL)
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{
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/* skip leading whitespace and check for # comment */
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char *ptr;
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TimeLineID tli;
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uint32 switchpoint_hi;
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uint32 switchpoint_lo;
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int nfields;
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for (ptr = fline; *ptr; ptr++)
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{
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if (!isspace((unsigned char) *ptr))
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break;
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}
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if (*ptr == '\0' || *ptr == '#')
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continue;
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nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
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if (nfields < 1)
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{
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/* expect a numeric timeline ID as first field of line */
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ereport(FATAL,
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(errmsg("syntax error in history file: %s", fline),
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errhint("Expected a numeric timeline ID.")));
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}
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if (nfields != 3)
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ereport(FATAL,
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(errmsg("syntax error in history file: %s", fline),
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errhint("Expected an XLOG switchpoint location.")));
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if (result && tli <= lasttli)
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ereport(FATAL,
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(errmsg("invalid data in history file: %s", fline),
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errhint("Timeline IDs must be in increasing sequence.")));
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lasttli = tli;
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entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
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entry->tli = tli;
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entry->begin = prevend;
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entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
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prevend = entry->end;
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/* Build list with newest item first */
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result = lcons(entry, result);
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/* we ignore the remainder of each line */
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}
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FreeFile(fd);
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if (result && targetTLI <= lasttli)
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ereport(FATAL,
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(errmsg("invalid data in history file \"%s\"", path),
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errhint("Timeline IDs must be less than child timeline's ID.")));
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/*
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* Create one more entry for the "tip" of the timeline, which has no
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* entry in the history file.
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*/
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entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
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entry->tli = targetTLI;
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entry->begin = prevend;
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entry->end = InvalidXLogRecPtr;
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result = lcons(entry, result);
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return result;
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}
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/*
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* Probe whether a timeline history file exists for the given timeline ID
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*/
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bool
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existsTimeLineHistory(TimeLineID probeTLI)
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{
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char path[MAXPGPATH];
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char histfname[MAXFNAMELEN];
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FILE *fd;
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/* Timeline 1 does not have a history file, so no need to check */
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if (probeTLI == 1)
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return false;
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if (InArchiveRecovery)
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{
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TLHistoryFileName(histfname, probeTLI);
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RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0, false);
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}
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else
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TLHistoryFilePath(path, probeTLI);
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fd = AllocateFile(path, "r");
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if (fd != NULL)
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{
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FreeFile(fd);
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return true;
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}
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else
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{
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if (errno != ENOENT)
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ereport(FATAL,
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(errcode_for_file_access(),
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errmsg("could not open file \"%s\": %m", path)));
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return false;
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}
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}
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/*
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* Find the newest existing timeline, assuming that startTLI exists.
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*
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* Note: while this is somewhat heuristic, it does positively guarantee
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* that (result + 1) is not a known timeline, and therefore it should
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* be safe to assign that ID to a new timeline.
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*/
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TimeLineID
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findNewestTimeLine(TimeLineID startTLI)
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{
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TimeLineID newestTLI;
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TimeLineID probeTLI;
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/*
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* The algorithm is just to probe for the existence of timeline history
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* files. XXX is it useful to allow gaps in the sequence?
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*/
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newestTLI = startTLI;
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for (probeTLI = startTLI + 1;; probeTLI++)
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{
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if (existsTimeLineHistory(probeTLI))
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{
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newestTLI = probeTLI; /* probeTLI exists */
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}
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else
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{
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/* doesn't exist, assume we're done */
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break;
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}
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}
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return newestTLI;
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}
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/*
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* Create a new timeline history file.
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*
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* newTLI: ID of the new timeline
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* parentTLI: ID of its immediate parent
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* switchpoint: XLOG position where the system switched to the new timeline
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* reason: human-readable explanation of why the timeline was switched
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*
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* Currently this is only used at the end recovery, and so there are no locking
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* considerations. But we should be just as tense as XLogFileInit to avoid
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* emplacing a bogus file.
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*/
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void
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writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
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XLogRecPtr switchpoint, char *reason)
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{
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char path[MAXPGPATH];
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char tmppath[MAXPGPATH];
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char histfname[MAXFNAMELEN];
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char buffer[BLCKSZ];
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int srcfd;
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int fd;
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int nbytes;
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Assert(newTLI > parentTLI); /* else bad selection of newTLI */
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/*
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* Write into a temp file name.
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*/
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snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid());
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unlink(tmppath);
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/* do not use get_sync_bit() here --- want to fsync only at end of fill */
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fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL,
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S_IRUSR | S_IWUSR);
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if (fd < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not create file \"%s\": %m", tmppath)));
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/*
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* If a history file exists for the parent, copy it verbatim
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*/
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if (InArchiveRecovery)
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{
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TLHistoryFileName(histfname, parentTLI);
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RestoreArchivedFile(path, histfname, "RECOVERYHISTORY", 0, false);
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}
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else
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TLHistoryFilePath(path, parentTLI);
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srcfd = OpenTransientFile(path, O_RDONLY, 0);
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if (srcfd < 0)
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{
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if (errno != ENOENT)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not open file \"%s\": %m", path)));
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/* Not there, so assume parent has no parents */
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}
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else
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{
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for (;;)
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{
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errno = 0;
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nbytes = (int) read(srcfd, buffer, sizeof(buffer));
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if (nbytes < 0 || errno != 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not read file \"%s\": %m", path)));
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if (nbytes == 0)
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break;
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errno = 0;
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if ((int) write(fd, buffer, nbytes) != nbytes)
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{
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int save_errno = errno;
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/*
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* If we fail to make the file, delete it to release disk
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* space
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*/
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unlink(tmppath);
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/*
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* if write didn't set errno, assume problem is no disk space
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*/
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errno = save_errno ? save_errno : ENOSPC;
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not write to file \"%s\": %m", tmppath)));
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}
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}
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CloseTransientFile(srcfd);
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}
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/*
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* Append one line with the details of this timeline split.
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*
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* If we did have a parent file, insert an extra newline just in case the
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* parent file failed to end with one.
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*/
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snprintf(buffer, sizeof(buffer),
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"%s%u\t%X/%X\t%s\n",
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(srcfd < 0) ? "" : "\n",
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parentTLI,
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(uint32) (switchpoint >> 32), (uint32) (switchpoint),
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reason);
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nbytes = strlen(buffer);
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errno = 0;
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if ((int) write(fd, buffer, nbytes) != nbytes)
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{
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int save_errno = errno;
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/*
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* If we fail to make the file, delete it to release disk space
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*/
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unlink(tmppath);
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/* if write didn't set errno, assume problem is no disk space */
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errno = save_errno ? save_errno : ENOSPC;
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not write to file \"%s\": %m", tmppath)));
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}
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if (pg_fsync(fd) != 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not fsync file \"%s\": %m", tmppath)));
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if (CloseTransientFile(fd))
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not close file \"%s\": %m", tmppath)));
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/*
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* Now move the completed history file into place with its final name.
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*/
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TLHistoryFilePath(path, newTLI);
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/*
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* Prefer link() to rename() here just to be really sure that we don't
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* overwrite an existing file. However, there shouldn't be one, so
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* rename() is an acceptable substitute except for the truly paranoid.
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*/
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#if HAVE_WORKING_LINK
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if (link(tmppath, path) < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not link file \"%s\" to \"%s\": %m",
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tmppath, path)));
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unlink(tmppath);
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#else
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if (rename(tmppath, path) < 0)
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ereport(ERROR,
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(errcode_for_file_access(),
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errmsg("could not rename file \"%s\" to \"%s\": %m",
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tmppath, path)));
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#endif
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/* The history file can be archived immediately. */
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TLHistoryFileName(histfname, newTLI);
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XLogArchiveNotify(histfname);
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}
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/*
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* Returns true if 'expectedTLEs' contains a timeline with id 'tli'
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*/
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bool
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tliInHistory(TimeLineID tli, List *expectedTLEs)
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{
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ListCell *cell;
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foreach(cell, expectedTLEs)
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{
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if (((TimeLineHistoryEntry *) lfirst(cell))->tli == tli)
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return true;
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}
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return false;
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}
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/*
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* Returns the ID of the timeline in use at a particular point in time, in
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* the given timeline history.
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*/
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TimeLineID
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tliOfPointInHistory(XLogRecPtr ptr, List *history)
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{
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ListCell *cell;
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foreach(cell, history)
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{
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TimeLineHistoryEntry *tle = (TimeLineHistoryEntry *) lfirst(cell);
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if ((XLogRecPtrIsInvalid(tle->begin) || XLByteLE(tle->begin, ptr)) &&
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(XLogRecPtrIsInvalid(tle->end) || XLByteLT(ptr, tle->end)))
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{
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/* found it */
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return tle->tli;
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}
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}
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/* shouldn't happen. */
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elog(ERROR, "timeline history was not contiguous");
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return 0; /* keep compiler quiet */
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}
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/*
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* Returns the point in history where we branched off the given timeline.
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* Returns InvalidXLogRecPtr if the timeline is current (= we have not
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* branched off from it), and throws an error if the timeline is not part of
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* this server's history.
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*/
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XLogRecPtr
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tliSwitchPoint(TimeLineID tli, List *history)
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{
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ListCell *cell;
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foreach (cell, history)
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{
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TimeLineHistoryEntry *tle = (TimeLineHistoryEntry *) lfirst(cell);
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if (tle->tli == tli)
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return tle->end;
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}
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ereport(ERROR,
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(errmsg("requested timeline %u is not in this server's history",
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tli)));
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return InvalidXLogRecPtr; /* keep compiler quiet */
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}
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