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Write exact xlog position of timeline switch in the timeline history file.

Browse Source 
This allows us to do some more rigorous sanity checking for various
incorrect point-in-time recovery scenarios, and provides more information
for debugging purposes. It will also come handy in the upcoming patch to
allow timeline switches to be replicated by streaming replication.
pull/3/head
Heikki Linnakangas 13 years ago
parent a84c30dda5
commit 32f4de0adf
3 changed files with 247 additions and 90 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 144
      src/backend/access/transam/timeline.c
  2. 173
      src/backend/access/transam/xlog.c
  3. 20
      src/include/access/timeline.h

144
src/backend/access/transam/timeline.c
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@ -12,10 +12,10 @@
*
* Each line in the file represents a timeline switch:
*
* <parentTLI> <xlogfname> <reason>
* <parentTLI> <switchpoint> <reason>
*
* parentTLI ID of the parent timeline
* xlogfname filename of the WAL segment where the switch happened
* switchpoint XLogRecPtr of the WAL position where the switch happened
* reason human-readable explanation of why the timeline was changed
*
* The fields are separated by tabs. Lines beginning with # are comments, and
@ -56,10 +56,18 @@ readTimeLineHistory(TimeLineID targetTLI)
char histfname[MAXFNAMELEN];
char fline[MAXPGPATH];
FILE *fd;
TimeLineHistoryEntry *entry;
TimeLineID lasttli = 0;
XLogRecPtr prevend;
/* Timeline 1 does not have a history file, so no need to check */
if (targetTLI == 1)
return list_make1_int((int) targetTLI);
{
entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
entry->tli = targetTLI;
entry->begin = entry->end = InvalidXLogRecPtr;
return list_make1(entry);
}
if (InArchiveRecovery)
{
@ -77,7 +85,10 @@ readTimeLineHistory(TimeLineID targetTLI)
(errcode_for_file_access(),
errmsg("could not open file \"%s\": %m", path)));
/* Not there, so assume no parents */
return list_make1_int((int) targetTLI);
entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
entry->tli = targetTLI;
entry->begin = entry->end = InvalidXLogRecPtr;
return list_make1(entry);
}
result = NIL;
@ -85,12 +96,15 @@ readTimeLineHistory(TimeLineID targetTLI)
/*
* Parse the file...
*/
prevend = InvalidXLogRecPtr;
while (fgets(fline, sizeof(fline), fd) != NULL)
{
/* skip leading whitespace and check for # comment */
char *ptr;
char *endptr;
TimeLineID tli;
uint32 switchpoint_hi;
uint32 switchpoint_lo;
int nfields;
for (ptr = fline; *ptr; ptr++)
{
@ -100,38 +114,56 @@ readTimeLineHistory(TimeLineID targetTLI)
if (*ptr == '\0' || *ptr == '#')
continue;
/* expect a numeric timeline ID as first field of line */
tli = (TimeLineID) strtoul(ptr, &endptr, 0);
if (endptr == ptr)
nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
if (nfields < 1)
{
/* expect a numeric timeline ID as first field of line */
ereport(FATAL,
(errmsg("syntax error in history file: %s", fline),
errhint("Expected a numeric timeline ID.")));
}
if (nfields != 3)
ereport(FATAL,
(errmsg("syntax error in history file: %s", fline),
errhint("Expected an XLOG switchpoint location.")));
if (result &&
tli <= (TimeLineID) linitial_int(result))
if (result && tli <= lasttli)
ereport(FATAL,
(errmsg("invalid data in history file: %s", fline),
errhint("Timeline IDs must be in increasing sequence.")));
lasttli = tli;
entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
entry->tli = tli;
entry->begin = prevend;
entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
prevend = entry->end;
/* Build list with newest item first */
result = lcons_int((int) tli, result);
result = lcons(entry, result);
/* we ignore the remainder of each line */
}
FreeFile(fd);
if (result &&
targetTLI <= (TimeLineID) linitial_int(result))
if (result && targetTLI <= lasttli)
ereport(FATAL,
(errmsg("invalid data in history file \"%s\"", path),
errhint("Timeline IDs must be less than child timeline's ID.")));
result = lcons_int((int) targetTLI, result);
/*
* Create one more entry for the "tip" of the timeline, which has no
* entry in the history file.
*/
entry = (TimeLineHistoryEntry *) palloc(sizeof(TimeLineHistoryEntry));
entry->tli = targetTLI;
entry->begin = prevend;
entry->end = InvalidXLogRecPtr;
ereport(DEBUG3,
(errmsg_internal("history of timeline %u is %s",
targetTLI, nodeToString(result))));
result = lcons(entry, result);
return result;
}
@ -214,7 +246,7 @@ findNewestTimeLine(TimeLineID startTLI)
*
* newTLI: ID of the new timeline
* parentTLI: ID of its immediate parent
* endTLI et al: ID of the last used WAL file, for annotation purposes
* switchpoint: XLOG position where the system switched to the new timeline
* reason: human-readable explanation of why the timeline was switched
*
* Currently this is only used at the end recovery, and so there are no locking
@ -223,12 +255,11 @@ findNewestTimeLine(TimeLineID startTLI)
*/
void
writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
TimeLineID endTLI, XLogSegNo endLogSegNo, char *reason)
XLogRecPtr switchpoint, char *reason)
{
char path[MAXPGPATH];
char tmppath[MAXPGPATH];
char histfname[MAXFNAMELEN];
char xlogfname[MAXFNAMELEN];
char buffer[BLCKSZ];
int srcfd;
int fd;
@ -313,13 +344,11 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
* If we did have a parent file, insert an extra newline just in case the
* parent file failed to end with one.
*/
XLogFileName(xlogfname, endTLI, endLogSegNo);
snprintf(buffer, sizeof(buffer),
"%s%u\t%s\t%s\n",
"%s%u\t%X/%X\t%s\n",
(srcfd < 0) ? "" : "\n",
parentTLI,
xlogfname,
(uint32) (switchpoint >> 32), (uint32) (switchpoint),
reason);
nbytes = strlen(buffer);
@ -380,3 +409,70 @@ writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
TLHistoryFileName(histfname, newTLI);
XLogArchiveNotify(histfname);
}
/*
* Returns true if 'expectedTLEs' contains a timeline with id 'tli'
*/
bool
tliInHistory(TimeLineID tli, List *expectedTLEs)
{
ListCell *cell;
foreach(cell, expectedTLEs)
{
if (((TimeLineHistoryEntry *) lfirst(cell))->tli == tli)
return true;
}
return false;
}
/*
* Returns the ID of the timeline in use at a particular point in time, in
* the given timeline history.
*/
TimeLineID
tliOfPointInHistory(XLogRecPtr ptr, List *history)
{
ListCell *cell;
foreach(cell, history)
{
TimeLineHistoryEntry *tle = (TimeLineHistoryEntry *) lfirst(cell);
if ((XLogRecPtrIsInvalid(tle->begin) || XLByteLE(tle->begin, ptr)) &&
(XLogRecPtrIsInvalid(tle->end) || XLByteLT(ptr, tle->end)))
{
/* found it */
return tle->tli;
}
}
/* shouldn't happen. */
elog(ERROR, "timeline history was not contiguous");
return 0; /* keep compiler quiet */
}
/*
* Returns the point in history where we branched off the given timeline.
* Returns InvalidXLogRecPtr if the timeline is current (= we have not
* branched off from it), and throws an error if the timeline is not part of
* this server's history.
*/
XLogRecPtr
tliSwitchPoint(TimeLineID tli, List *history)
{
ListCell *cell;
foreach (cell, history)
{
TimeLineHistoryEntry *tle = (TimeLineHistoryEntry *) lfirst(cell);
if (tle->tli == tli)
return tle->end;
}
ereport(ERROR,
(errmsg("requested timeline %u is not in this server's history",
tli)));
return InvalidXLogRecPtr; /* keep compiler quiet */
}

173
src/backend/access/transam/xlog.c
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@ -226,7 +226,7 @@ static bool recoveryStopAfter;
*
* recoveryTargetIsLatest: was the requested target timeline 'latest'?
*
* expectedTLIs: an integer list of recoveryTargetTLI and the TLIs of
* expectedTLEs: a list of TimeLineHistoryEntries for recoveryTargetTLI and the timelines of
* its known parents, newest first (so recoveryTargetTLI is always the
* first list member). Only these TLIs are expected to be seen in the WAL
* segments we read, and indeed only these TLIs will be considered as
@ -240,7 +240,7 @@ static bool recoveryStopAfter;
*/
static TimeLineID recoveryTargetTLI;
static bool recoveryTargetIsLatest = false;
static List *expectedTLIs;
static List *expectedTLEs;
static TimeLineID curFileTLI;
/*
@ -2515,7 +2515,7 @@ InstallXLogFileSegment(XLogSegNo *segno, char *tmppath,
/*
* Prefer link() to rename() here just to be really sure that we don't
* overwrite an existing logfile. However, there shouldn't be one, so
* overwrite an existing file. However, there shouldn't be one, so
* rename() is an acceptable substitute except for the truly paranoid.
*/
#if HAVE_WORKING_LINK
@ -2716,7 +2716,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
/*
* Open a logfile segment for reading (during recovery).
*
* This version searches for the segment with any TLI listed in expectedTLIs.
* This version searches for the segment with any TLI listed in expectedTLEs.
*/
static int
XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
@ -2727,7 +2727,7 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
/*
* Loop looking for a suitable timeline ID: we might need to read any of
* the timelines listed in expectedTLIs.
* the timelines listed in expectedTLEs.
*
* We expect curFileTLI on entry to be the TLI of the preceding file in
* sequence, or 0 if there was no predecessor. We do not allow curFileTLI
@ -2735,9 +2735,9 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
* parent timeline extends to higher segment numbers than the child we
* want to read.
*/
foreach(cell, expectedTLIs)
foreach(cell, expectedTLEs)
{
TimeLineID tli = (TimeLineID) lfirst_int(cell);
TimeLineID tli = ((TimeLineHistoryEntry *) lfirst(cell))->tli;
if (tli < curFileTLI)
break; /* don't bother looking at too-old TLIs */
@ -3344,7 +3344,7 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
/*
* Since we are going to a random position in WAL, forget any prior
* state about what timeline we were in, and allow it to be any
* timeline in expectedTLIs. We also set a flag to allow curFileTLI
* timeline in expectedTLEs. We also set a flag to allow curFileTLI
* to go backwards (but we can't reset that variable right here, since
* we might not change files at all).
*/
@ -3675,7 +3675,7 @@ ValidXLogPageHeader(XLogPageHeader hdr, int emode, bool segmentonly)
/*
* Check page TLI is one of the expected values.
*/
if (!list_member_int(expectedTLIs, (int) hdr->xlp_tli))
if (!tliInHistory(hdr->xlp_tli, expectedTLEs))
{
ereport(emode_for_corrupt_record(emode, recaddr),
(errmsg("unexpected timeline ID %u in log segment %s, offset %u",
@ -3812,57 +3812,86 @@ ValidXLogRecordHeader(XLogRecPtr *RecPtr, XLogRecord *record, int emode,
static bool
rescanLatestTimeLine(void)
{
List *newExpectedTLEs;
bool found;
ListCell *cell;
TimeLineID newtarget;
TimeLineHistoryEntry *currentTle = NULL;
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
newtarget = findNewestTimeLine(recoveryTargetTLI);
if (newtarget != recoveryTargetTLI)
if (newtarget == recoveryTargetTLI)
{
/*
* Determine the list of expected TLIs for the new TLI
*/
List *newExpectedTLIs;
newExpectedTLIs = readTimeLineHistory(newtarget);
/* No new timelines found */
return false;
}
/*
* If the current timeline is not part of the history of the new
* timeline, we cannot proceed to it.
*
* XXX This isn't foolproof: The new timeline might have forked from
* the current one, but before the current recovery location. In that
* case we will still switch to the new timeline and proceed replaying
* from it even though the history doesn't match what we already
* replayed. That's not good. We will likely notice at the next online
* checkpoint, as the TLI won't match what we expected, but it's not
* guaranteed. The admin needs to make sure that doesn't happen.
*/
if (!list_member_int(newExpectedTLIs,
(int) recoveryTargetTLI))
ereport(LOG,
(errmsg("new timeline %u is not a child of database system timeline %u",
newtarget,
ThisTimeLineID)));
else
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
/*
* Determine the list of expected TLIs for the new TLI
*/
/* Switch target */
recoveryTargetTLI = newtarget;
list_free(expectedTLIs);
expectedTLIs = newExpectedTLIs;
newExpectedTLEs = readTimeLineHistory(newtarget);
SpinLockAcquire(&xlogctl->info_lck);
xlogctl->RecoveryTargetTLI = recoveryTargetTLI;
SpinLockRelease(&xlogctl->info_lck);
/*
* If the current timeline is not part of the history of the new
* timeline, we cannot proceed to it.
*/
found = false;
foreach (cell, newExpectedTLEs)
{
currentTle = (TimeLineHistoryEntry *) lfirst(cell);
ereport(LOG,
(errmsg("new target timeline is %u",
recoveryTargetTLI)));
return true;
if (currentTle->tli == recoveryTargetTLI)
{
found = true;
break;
}
}
return false;
if (!found)
{
ereport(LOG,
(errmsg("new timeline %u is not a child of database system timeline %u",
newtarget,
ThisTimeLineID)));
return false;
}
/*
* The current timeline was found in the history file, but check that the
* next timeline was forked off from it *after* the current recovery
* location.
*/
if (XLByteLT(currentTle->end, EndRecPtr))
{
ereport(LOG,
(errmsg("new timeline %u forked off current database system timeline %u before current recovery point %X/%X",
newtarget,
ThisTimeLineID,
(uint32) (EndRecPtr >> 32), (uint32) EndRecPtr)));
return false;
}
/* The new timeline history seems valid. Switch target */
recoveryTargetTLI = newtarget;
list_free_deep(expectedTLEs);
expectedTLEs = newExpectedTLEs;
SpinLockAcquire(&xlogctl->info_lck);
xlogctl->RecoveryTargetTLI = recoveryTargetTLI;
SpinLockRelease(&xlogctl->info_lck);
ereport(LOG,
(errmsg("new target timeline is %u",
recoveryTargetTLI)));
/*
* Wake up any walsenders to notice that we have a new target timeline.
*/
if (AllowCascadeReplication())
WalSndWakeup();
return true;
}
/*
@ -5300,26 +5329,41 @@ StartupXLOG(void)
readRecoveryCommandFile();
/* Now we can determine the list of expected TLIs */
expectedTLIs = readTimeLineHistory(recoveryTargetTLI);
expectedTLEs = readTimeLineHistory(recoveryTargetTLI);
/*
* If pg_control's timeline is not in expectedTLIs, then we cannot
* proceed: the backup is not part of the history of the requested
* timeline.
* If the location of the checkpoint record is not on the expected
* timeline in the history of the requested timeline, we cannot proceed:
* the backup is not part of the history of the requested timeline.
*/
if (!list_member_int(expectedTLIs,
(int) ControlFile->checkPointCopy.ThisTimeLineID))
if (tliOfPointInHistory(ControlFile->checkPoint, expectedTLEs) !=
ControlFile->checkPointCopy.ThisTimeLineID)
{
XLogRecPtr switchpoint;
/*
* tliSwitchPoint will throw an error if the checkpoint's timeline
* is not in expectedTLEs at all.
*/
switchpoint = tliSwitchPoint(ControlFile->checkPointCopy.ThisTimeLineID, expectedTLEs);
ereport(FATAL,
(errmsg("requested timeline %u is not a child of database system timeline %u",
recoveryTargetTLI,
ControlFile->checkPointCopy.ThisTimeLineID)));
(errmsg("requested timeline %u is not a child of this server's history",
recoveryTargetTLI),
errdetail("Latest checkpoint is at %X/%X on timeline %u, but in the history of the requested timeline, the server forked off from that timeline at %X/%X",
(uint32) (ControlFile->checkPoint >> 32),
(uint32) ControlFile->checkPoint,
ControlFile->checkPointCopy.ThisTimeLineID,
(uint32) (switchpoint >> 32),
(uint32) switchpoint)));
}
/*
* The min recovery point should be part of the requested timeline's
* history, too.
*/
if (!XLogRecPtrIsInvalid(ControlFile->minRecoveryPoint) &&
!list_member_int(expectedTLIs, ControlFile->minRecoveryPointTLI))
tliOfPointInHistory(ControlFile->minRecoveryPoint - 1, expectedTLEs) !=
ControlFile->minRecoveryPointTLI)
ereport(FATAL,
(errmsg("requested timeline %u does not contain minimum recovery point %X/%X on timeline %u",
recoveryTargetTLI,
@ -6026,8 +6070,8 @@ StartupXLOG(void)
(errmsg("selected new timeline ID: %u", ThisTimeLineID)));
/*
* Write comment to history file to explain why and where timeline
* changed. Comment varies according to the recovery target used.
* Create a comment for the history file to explain why and where
* timeline changed.
*/
if (recoveryTarget == RECOVERY_TARGET_XID)
snprintf(reason, sizeof(reason),
@ -6047,7 +6091,7 @@ StartupXLOG(void)
snprintf(reason, sizeof(reason), "no recovery target specified");
writeTimeLineHistory(ThisTimeLineID, recoveryTargetTLI,
curFileTLI, endLogSegNo, reason);
EndRecPtr, reason);
}
/* Save the selected TimeLineID in shared memory, too */
@ -7916,8 +7960,7 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
* decrease.
*/
if (checkPoint.ThisTimeLineID < ThisTimeLineID ||
!list_member_int(expectedTLIs,
(int) checkPoint.ThisTimeLineID))
!tliInHistory(checkPoint.ThisTimeLineID, expectedTLEs))
ereport(PANIC,
(errmsg("unexpected timeline ID %u (after %u) in checkpoint record",
checkPoint.ThisTimeLineID, ThisTimeLineID)));

20
src/include/access/timeline.h
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@ -14,10 +14,28 @@
#include "access/xlogdefs.h"
#include "nodes/pg_list.h"
/*
* A list of these structs describes the timeline history of the server. Each
* TimeLineHistoryEntry represents a piece of WAL belonging to the history,
* from newest to oldest. All WAL positions between 'begin' and 'end' belong to
* the timeline represented by the entry. Together the 'begin' and 'end'
* pointers of all the entries form a contiguous line from beginning of time
* to infinity.
*/
typedef struct
{
TimeLineID tli;
XLogRecPtr begin; /* inclusive */
XLogRecPtr end; /* exclusive, 0 means infinity */
} TimeLineHistoryEntry;
extern List *readTimeLineHistory(TimeLineID targetTLI);
extern bool existsTimeLineHistory(TimeLineID probeTLI);
extern TimeLineID findNewestTimeLine(TimeLineID startTLI);
extern void writeTimeLineHistory(TimeLineID newTLI, TimeLineID parentTLI,
TimeLineID endTLI, XLogSegNo endLogSegNo, char *reason);
XLogRecPtr switchpoint, char *reason);
extern bool tliInHistory(TimeLineID tli, List *expectedTLIs);
extern TimeLineID tliOfPointInHistory(XLogRecPtr ptr, List *history);
extern XLogRecPtr tliSwitchPoint(TimeLineID tli, List *history);
#endif /* TIMELINE_H */

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