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Add WAL consistency checking facility.

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When the new GUC wal_consistency_checking is set to a non-empty value,
it triggers recording of additional full-page images, which are
compared on the standby against the results of applying the WAL record
(without regard to those full-page images).  Allowable differences
such as hints are masked out, and the resulting pages are compared;
any difference results in a FATAL error on the standby.

Kuntal Ghosh, based on earlier patches by Michael Paquier and Heikki
Linnakangas.  Extensively reviewed and revised by Michael Paquier and
by me, with additional reviews and comments from Amit Kapila, Álvaro
Herrera, Simon Riggs, and Peter Eisentraut.
This commit is contained in:
Robert Haas
2017-02-08 15:45:30 -05:00
parent 115cb31597
commit a507b86900
36 changed files with 811 additions and 48 deletions
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38
src/backend/access/transam/xloginsert.c
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@ -421,10 +421,12 @@ XLogInsert(RmgrId rmid, uint8 info)
elog(ERROR, "XLogBeginInsert was not called");
/*
* The caller can set rmgr bits and XLR_SPECIAL_REL_UPDATE; the rest are
* reserved for use by me.
* The caller can set rmgr bits, XLR_SPECIAL_REL_UPDATE and
* XLR_CHECK_CONSISTENCY; the rest are reserved for use by me.
*/
if ((info & ~(XLR_RMGR_INFO_MASK | XLR_SPECIAL_REL_UPDATE)) != 0)
if ((info & ~(XLR_RMGR_INFO_MASK |
XLR_SPECIAL_REL_UPDATE |
XLR_CHECK_CONSISTENCY)) != 0)
elog(PANIC, "invalid xlog info mask %02X", info);
TRACE_POSTGRESQL_XLOG_INSERT(rmid, info);
@ -504,6 +506,15 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
rdt_datas_last = &hdr_rdt;
hdr_rdt.data = hdr_scratch;
/*
* Enforce consistency checks for this record if user is looking for
* it. Do this before at the beginning of this routine to give the
* possibility for callers of XLogInsert() to pass XLR_CHECK_CONSISTENCY
* directly for a record.
*/
if (wal_consistency_checking[rmid])
info |= XLR_CHECK_CONSISTENCY;
/*
* Make an rdata chain containing all the data portions of all block
* references. This includes the data for full-page images. Also append
@ -520,6 +531,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
XLogRecordBlockCompressHeader cbimg = {0};
bool samerel;
bool is_compressed = false;
bool include_image;
if (!regbuf->in_use)
continue;
@ -563,7 +575,14 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
if ((regbuf->flags & REGBUF_WILL_INIT) == REGBUF_WILL_INIT)
bkpb.fork_flags |= BKPBLOCK_WILL_INIT;
if (needs_backup)
/*
* If needs_backup is true or WAL checking is enabled for
* current resource manager, log a full-page write for the current
* block.
*/
include_image = needs_backup || (info & XLR_CHECK_CONSISTENCY) != 0;
if (include_image)
{
Page page = regbuf->page;
uint16 compressed_len;
@ -625,6 +644,15 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
bimg.bimg_info = (cbimg.hole_length == 0) ? 0 : BKPIMAGE_HAS_HOLE;
/*
* If WAL consistency checking is enabled for the resource manager of
* this WAL record, a full-page image is included in the record
* for the block modified. During redo, the full-page is replayed
* only if BKPIMAGE_APPLY is set.
*/
if (needs_backup)
bimg.bimg_info |= BKPIMAGE_APPLY;
if (is_compressed)
{
bimg.length = compressed_len;
@ -687,7 +715,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
/* Ok, copy the header to the scratch buffer */
memcpy(scratch, &bkpb, SizeOfXLogRecordBlockHeader);
scratch += SizeOfXLogRecordBlockHeader;
if (needs_backup)
if (include_image)
{
memcpy(scratch, &bimg, SizeOfXLogRecordBlockImageHeader);
scratch += SizeOfXLogRecordBlockImageHeader;