Add pg_xlogdump contrib program

This program relies on rm_desc backend routines and the xlogreader
infrastructure to emit human-readable rendering of WAL records.

Author: Andres Freund, with many reworks by Álvaro
Reviewed (in a much earlier version) by Peter Eisentraut

1 files changed, 711 insertions, 0 deletions

diff --git a/contrib/pg_xlogdump/pg_xlogdump.c b/contrib/pg_xlogdump/pg_xlogdump.c
new file mode 100644
index 00000000000..aef21898fb8
--- /dev/null
+++ b/contrib/pg_xlogdump/pg_xlogdump.c
@@ -0,0 +1,711 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_xlogdump.c - decode and display WAL
+ *
+ * Copyright (c) 2012, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		  contrib/pg_xlogdump/pg_xlogdump.c
+ *-------------------------------------------------------------------------
+ */
+
+#define FRONTEND 1
+#include "postgres.h"
+
+#include <dirent.h>
+#include <unistd.h>
+
+#include "access/xlog.h"
+#include "access/xlogreader.h"
+#include "access/transam.h"
+#include "common/fe_memutils.h"
+#include "common/relpath.h"
+#include "getopt_long.h"
+#include "rmgrdesc.h"
+
+
+static const char *progname;
+
+typedef struct XLogDumpPrivate
+{
+	TimeLineID	timeline;
+	char	   *inpath;
+	XLogRecPtr	startptr;
+	XLogRecPtr	endptr;
+} XLogDumpPrivate;
+
+typedef struct XLogDumpConfig
+{
+	/* display options */
+	bool		bkp_details;
+	int			stop_after_records;
+	int			already_displayed_records;
+
+	/* filter options */
+	int			filter_by_rmgr;
+	TransactionId filter_by_xid;
+	TransactionId filter_by_xid_enabled;
+} XLogDumpConfig;
+
+static void
+fatal_error(const char *fmt,...)
+__attribute__((format(PG_PRINTF_ATTRIBUTE, 1, 2)));
+
+/*
+ * Big red button to push when things go horribly wrong.
+ */
+static void
+fatal_error(const char *fmt,...)
+{
+	va_list		args;
+
+	fflush(stdout);
+
+	fprintf(stderr, "%s: FATAL:  ", progname);
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+	fputc('\n', stderr);
+
+	exit(EXIT_FAILURE);
+}
+
+static void
+print_rmgr_list(void)
+{
+	int		i;
+
+	for (i = 0; i < RM_MAX_ID + 1; i++)
+	{
+		printf("%s\n", RmgrDescTable[i].rm_name);
+	}
+}
+
+/*
+ * Check whether directory exists and whether we can open it. Keep errno set so
+ * that the caller can report errors somewhat more accurately.
+ */
+static bool
+verify_directory(const char *directory)
+{
+	DIR *dir = opendir(directory);
+	if (dir == NULL)
+		return false;
+	closedir(dir);
+	return true;
+}
+
+/*
+ * Split a pathname as dirname(1) and basename(1) would.
+ *
+ * XXX this probably doesn't do very well on Windows.  We probably need to
+ * apply canonicalize_path(), at the very least.
+ */
+static void
+split_path(const char *path, char **dir, char **fname)
+{
+	char	   *sep;
+
+	/* split filepath into directory & filename */
+	sep = strrchr(path, '/');
+
+	/* directory path */
+	if (sep != NULL)
+	{
+		*dir = pg_strdup(path);
+		(*dir)[(sep - path) + 1] = '\0';	/* no strndup */
+		*fname = pg_strdup(sep + 1);
+	}
+	/* local directory */
+	else
+	{
+		*dir = NULL;
+		*fname = pg_strdup(path);
+	}
+}
+
+/*
+ * Try to find the file in several places:
+ * if directory == NULL:
+ *	 fname
+ *	 XLOGDIR / fname
+ *	 $PGDATA / XLOGDIR / fname
+ * else
+ *	 directory / fname
+ *	 directory / XLOGDIR / fname
+ *
+ * return a read only fd
+ */
+static int
+fuzzy_open_file(const char *directory, const char *fname)
+{
+	int			fd = -1;
+	char		fpath[MAXPGPATH];
+
+	if (directory == NULL)
+	{
+		const char *datadir;
+
+		/* fname */
+		fd = open(fname, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		/* XLOGDIR / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s",
+				 XLOGDIR, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		datadir = getenv("PGDATA");
+		/* $PGDATA / XLOGDIR / fname */
+		if (datadir != NULL)
+		{
+			snprintf(fpath, MAXPGPATH, "%s/%s/%s",
+					 datadir, XLOGDIR, fname);
+			fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+			if (fd < 0 && errno != ENOENT)
+				return -1;
+			else if (fd > 0)
+				return fd;
+		}
+	}
+	else
+	{
+		/* directory / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s",
+				 directory, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+
+		/* directory / XLOGDIR / fname */
+		snprintf(fpath, MAXPGPATH, "%s/%s/%s",
+				 directory, XLOGDIR, fname);
+		fd = open(fpath, O_RDONLY | PG_BINARY, 0);
+		if (fd < 0 && errno != ENOENT)
+			return -1;
+		else if (fd > 0)
+			return fd;
+	}
+	return -1;
+}
+
+/*
+ * Read count bytes from a segment file in the specified directory, for the
+ * given timeline, containing the specified record pointer; store the data in
+ * the passed buffer.
+ */
+static void
+XLogDumpXLogRead(const char *directory, TimeLineID timeline_id,
+				 XLogRecPtr startptr, char *buf, Size count)
+{
+	char	   *p;
+	XLogRecPtr	recptr;
+	Size		nbytes;
+
+	static int	sendFile = -1;
+	static XLogSegNo sendSegNo = 0;
+	static uint32 sendOff = 0;
+
+	p = buf;
+	recptr = startptr;
+	nbytes = count;
+
+	while (nbytes > 0)
+	{
+		uint32		startoff;
+		int			segbytes;
+		int			readbytes;
+
+		startoff = recptr % XLogSegSize;
+
+		if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo))
+		{
+			char		fname[MAXFNAMELEN];
+
+			/* Switch to another logfile segment */
+			if (sendFile >= 0)
+				close(sendFile);
+
+			XLByteToSeg(recptr, sendSegNo);
+
+			XLogFileName(fname, timeline_id, sendSegNo);
+
+			sendFile = fuzzy_open_file(directory, fname);
+
+			if (sendFile < 0)
+				fatal_error("could not find file \"%s\": %s",
+							fname, strerror(errno));
+			sendOff = 0;
+		}
+
+		/* Need to seek in the file? */
+		if (sendOff != startoff)
+		{
+			if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
+			{
+				int			err = errno;
+				char		fname[MAXPGPATH];
+
+				XLogFileName(fname, timeline_id, sendSegNo);
+
+				fatal_error("could not seek in log segment %s to offset %u: %s",
+							fname, startoff, strerror(err));
+			}
+			sendOff = startoff;
+		}
+
+		/* How many bytes are within this segment? */
+		if (nbytes > (XLogSegSize - startoff))
+			segbytes = XLogSegSize - startoff;
+		else
+			segbytes = nbytes;
+
+		readbytes = read(sendFile, p, segbytes);
+		if (readbytes <= 0)
+		{
+			int			err = errno;
+			char		fname[MAXPGPATH];
+
+			XLogFileName(fname, timeline_id, sendSegNo);
+
+			fatal_error("could not read from log segment %s, offset %d, length %d: %s",
+						fname, sendOff, segbytes, strerror(err));
+		}
+
+		/* Update state for read */
+		recptr += readbytes;
+
+		sendOff += readbytes;
+		nbytes -= readbytes;
+		p += readbytes;
+	}
+}
+
+/*
+ * XLogReader read_page callback
+ */
+static int
+XLogDumpReadPage(XLogReaderState *state, XLogRecPtr targetPagePtr, int reqLen,
+				 XLogRecPtr targetPtr, char *readBuff, TimeLineID *curFileTLI)
+{
+	XLogDumpPrivate *private = state->private_data;
+	int			count = XLOG_BLCKSZ;
+
+	if (private->endptr != InvalidXLogRecPtr)
+	{
+		if (targetPagePtr + XLOG_BLCKSZ <= private->endptr)
+			count = XLOG_BLCKSZ;
+		else if (targetPagePtr + reqLen <= private->endptr)
+			count = private->endptr - targetPagePtr;
+		else
+			return -1;
+	}
+
+	XLogDumpXLogRead(private->inpath, private->timeline, targetPagePtr,
+					 readBuff, count);
+
+	return count;
+}
+
+/*
+ * Print a record to stdout
+ */
+static void
+XLogDumpDisplayRecord(XLogDumpConfig *config, XLogRecPtr ReadRecPtr, XLogRecord *record)
+{
+	const RmgrDescData *desc = &RmgrDescTable[record->xl_rmid];
+
+	if (config->filter_by_rmgr != -1 &&
+		config->filter_by_rmgr != record->xl_rmid)
+		return;
+
+	if (config->filter_by_xid_enabled &&
+		config->filter_by_xid != record->xl_xid)
+		return;
+
+	config->already_displayed_records++;
+
+	printf("rmgr: %-11s len (rec/tot): %6u/%6u, tx: %10u, lsn: %X/%08X, prev %X/%08X, bkp: %u%u%u%u, desc: ",
+		   desc->rm_name,
+		   record->xl_len, record->xl_tot_len,
+		   record->xl_xid,
+		   (uint32) (ReadRecPtr >> 32), (uint32) ReadRecPtr,
+		   (uint32) (record->xl_prev >> 32), (uint32) record->xl_prev,
+		   !!(XLR_BKP_BLOCK(0) & record->xl_info),
+		   !!(XLR_BKP_BLOCK(1) & record->xl_info),
+		   !!(XLR_BKP_BLOCK(2) & record->xl_info),
+		   !!(XLR_BKP_BLOCK(3) & record->xl_info));
+
+	/* the desc routine will printf the description directly to stdout */
+	desc->rm_desc(NULL, record->xl_info, XLogRecGetData(record));
+
+	putchar('\n');
+
+	if (config->bkp_details)
+	{
+		int			bkpnum;
+		char	   *blk = (char *) XLogRecGetData(record) + record->xl_len;
+
+		for (bkpnum = 0; bkpnum < XLR_MAX_BKP_BLOCKS; bkpnum++)
+		{
+			BkpBlock	bkpb;
+
+			if (!(XLR_BKP_BLOCK(bkpnum) & record->xl_info))
+				continue;
+
+			memcpy(&bkpb, blk, sizeof(BkpBlock));
+			blk += sizeof(BkpBlock);
+			blk += BLCKSZ - bkpb.hole_length;
+
+			printf("\tbackup bkp #%u; rel %u/%u/%u; fork: %s; block: %u; hole: offset: %u, length: %u\n",
+				   bkpnum,
+				   bkpb.node.spcNode, bkpb.node.dbNode, bkpb.node.relNode,
+				   forkNames[bkpb.fork],
+				   bkpb.block, bkpb.hole_offset, bkpb.hole_length);
+		}
+	}
+}
+
+static void
+usage(void)
+{
+	printf("%s decodes and displays PostgreSQL transaction logs for debugging.\n\n",
+		   progname);
+	printf("Usage:\n");
+	printf("  %s [OPTION] [STARTSEG [ENDSEG]] \n", progname);
+	printf("\nGeneral options:\n");
+	printf("  -V, --version          output version information, then exit\n");
+	printf("  -?, --help             show this help, then exit\n");
+	printf("\nContent options:\n");
+	printf("  -b, --bkp-details      output detailed information about backup blocks\n");
+	printf("  -e, --end=RECPTR       stop reading at log position RECPTR\n");
+	printf("  -n, --limit=N          number of records to display\n");
+	printf("  -p, --path=PATH        directory in which to find log segment files\n");
+	printf("                         (default: ./pg_xlog)\n");
+	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
+	printf("                         use --rmgr=list to list valid resource manager names\n");
+	printf("  -s, --start=RECPTR     stop reading at log position RECPTR\n");
+	printf("  -t, --timeline=TLI     timeline from which to read log records\n");
+	printf("                         (default: 1 or the value used in STARTSEG)\n");
+	printf("  -x, --xid=XID          only show records with TransactionId XID\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	uint32		xlogid;
+	uint32		xrecoff;
+	XLogReaderState *xlogreader_state;
+	XLogDumpPrivate private;
+	XLogDumpConfig config;
+	XLogRecord *record;
+	XLogRecPtr	first_record;
+	char	   *errormsg;
+
+	static struct option long_options[] = {
+		{"bkp-details", no_argument, NULL, 'b'},
+		{"end", required_argument, NULL, 'e'},
+		{"help", no_argument, NULL, '?'},
+		{"limit", required_argument, NULL, 'n'},
+		{"path", required_argument, NULL, 'p'},
+		{"rmgr", required_argument, NULL, 'r'},
+		{"start", required_argument, NULL, 's'},
+		{"timeline", required_argument, NULL, 't'},
+		{"xid", required_argument, NULL, 'x'},
+		{"version", no_argument, NULL, 'V'},
+		{NULL, 0, NULL, 0}
+	};
+
+	int			option;
+	int			optindex = 0;
+
+	progname = get_progname(argv[0]);
+
+	memset(&private, 0, sizeof(XLogDumpPrivate));
+	memset(&config, 0, sizeof(XLogDumpConfig));
+
+	private.timeline = 1;
+	private.startptr = InvalidXLogRecPtr;
+	private.endptr = InvalidXLogRecPtr;
+
+	config.bkp_details = false;
+	config.stop_after_records = -1;
+	config.already_displayed_records = 0;
+	config.filter_by_rmgr = -1;
+	config.filter_by_xid = InvalidTransactionId;
+	config.filter_by_xid_enabled = false;
+
+	if (argc <= 1)
+	{
+		fprintf(stderr, "%s: no arguments specified\n", progname);
+		goto bad_argument;
+	}
+
+	while ((option = getopt_long(argc, argv, "be:?n:p:r:s:t:Vx:",
+								 long_options, &optindex)) != -1)
+	{
+		switch (option)
+		{
+			case 'b':
+				config.bkp_details = true;
+				break;
+			case 'e':
+				if (sscanf(optarg, "%X/%X", &xlogid, &xrecoff) != 2)
+				{
+					fprintf(stderr, "%s: could not parse end log position \"%s\"\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				private.endptr = (uint64) xlogid << 32 | xrecoff;
+				break;
+			case '?':
+				usage();
+				exit(EXIT_SUCCESS);
+				break;
+			case 'n':
+				if (sscanf(optarg, "%d", &config.stop_after_records) != 1)
+				{
+					fprintf(stderr, "%s: could not parse limit \"%s\"\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				break;
+			case 'p':
+				private.inpath = pg_strdup(optarg);
+				break;
+			case 'r':
+				{
+					int			i;
+
+					if (pg_strcasecmp(optarg, "list") == 0)
+					{
+						print_rmgr_list();
+						exit(EXIT_SUCCESS);
+					}
+
+					for (i = 0; i < RM_MAX_ID; i++)
+					{
+						if (pg_strcasecmp(optarg, RmgrDescTable[i].rm_name) == 0)
+						{
+							config.filter_by_rmgr = i;
+							break;
+						}
+					}
+
+					if (config.filter_by_rmgr == -1)
+					{
+						fprintf(stderr, "%s: resource manager \"%s\" does not exist\n",
+								progname, optarg);
+						goto bad_argument;
+					}
+				}
+				break;
+			case 's':
+				if (sscanf(optarg, "%X/%X", &xlogid, &xrecoff) != 2)
+				{
+					fprintf(stderr, "%s: could not parse end log position \"%s\"\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				else
+					private.startptr = (uint64) xlogid << 32 | xrecoff;
+				break;
+			case 't':
+				if (sscanf(optarg, "%d", &private.timeline) != 1)
+				{
+					fprintf(stderr, "%s: could not parse timeline \"%s\"\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				break;
+			case 'V':
+				puts("pg_xlogdump (PostgreSQL) " PG_VERSION);
+				exit(EXIT_SUCCESS);
+				break;
+			case 'x':
+				if (sscanf(optarg, "%u", &config.filter_by_xid) != 1)
+				{
+					fprintf(stderr, "%s: could not parse \"%s\" as a valid xid\n",
+							progname, optarg);
+					goto bad_argument;
+				}
+				config.filter_by_xid_enabled = true;
+				break;
+			default:
+				goto bad_argument;
+		}
+	}
+
+	if ((optind + 2) < argc)
+	{
+		fprintf(stderr,
+				"%s: too many command-line arguments (first is \"%s\")\n",
+				progname, argv[optind + 2]);
+		goto bad_argument;
+	}
+
+	if (private.inpath != NULL)
+	{
+		/* validate path points to directory */
+		if (!verify_directory(private.inpath))
+		{
+			fprintf(stderr,
+					"%s: path \"%s\" cannot be opened: %s",
+					progname, private.inpath, strerror(errno));
+			goto bad_argument;
+		}
+	}
+
+	/* parse files as start/end boundaries, extract path if not specified */
+	if (optind < argc)
+	{
+		char	   *directory = NULL;
+		char	   *fname = NULL;
+		int			fd;
+		XLogSegNo	segno;
+
+		split_path(argv[optind], &directory, &fname);
+
+		if (private.inpath == NULL && directory != NULL)
+		{
+			private.inpath = directory;
+
+			if (!verify_directory(private.inpath))
+				fatal_error("cannot open directory \"%s\": %s",
+							private.inpath, strerror(errno));
+		}
+
+		fd = fuzzy_open_file(private.inpath, fname);
+		if (fd < 0)
+			fatal_error("could not open file \"%s\"", fname);
+		close(fd);
+
+		/* parse position from file */
+		XLogFromFileName(fname, &private.timeline, &segno);
+
+		if (XLogRecPtrIsInvalid(private.startptr))
+			XLogSegNoOffsetToRecPtr(segno, 0, private.startptr);
+		else if (!XLByteInSeg(private.startptr, segno))
+		{
+			fprintf(stderr,
+					"%s: start log position %X/%X is not inside file \"%s\"\n",
+					progname,
+					(uint32) (private.startptr >> 32),
+					(uint32) private.startptr,
+					fname);
+			goto bad_argument;
+		}
+
+		/* no second file specified, set end position */
+		if (!(optind + 1 < argc) && XLogRecPtrIsInvalid(private.endptr))
+			XLogSegNoOffsetToRecPtr(segno + 1, 0, private.endptr);
+
+		/* parse ENDSEG if passed */
+		if (optind + 1 < argc)
+		{
+			XLogSegNo	endsegno;
+
+			/* ignore directory, already have that */
+			split_path(argv[optind + 1], &directory, &fname);
+
+			fd = fuzzy_open_file(private.inpath, fname);
+			if (fd < 0)
+				fatal_error("could not open file \"%s\"", fname);
+			close(fd);
+
+			/* parse position from file */
+			XLogFromFileName(fname, &private.timeline, &endsegno);
+
+			if (endsegno < segno)
+				fatal_error("ENDSEG %s is before STARTSEG %s",
+							argv[optind + 1], argv[optind]);
+
+			if (XLogRecPtrIsInvalid(private.endptr))
+				XLogSegNoOffsetToRecPtr(endsegno + 1, 0, private.endptr);
+
+			/* set segno to endsegno for check of --end */
+			segno = endsegno;
+		}
+
+
+		if (!XLByteInSeg(private.endptr, segno) &&
+			private.endptr != (segno + 1) * XLogSegSize)
+		{
+			fprintf(stderr,
+					"%s: end log position %X/%X is not inside file \"%s\"\n",
+					progname,
+					(uint32) (private.endptr >> 32),
+					(uint32) private.endptr,
+					argv[argc - 1]);
+			goto bad_argument;
+		}
+	}
+
+	/* we don't know what to print */
+	if (XLogRecPtrIsInvalid(private.startptr))
+	{
+		fprintf(stderr, "%s: no start log position given in range mode.\n", progname);
+		goto bad_argument;
+	}
+
+	/* done with argument parsing, do the actual work */
+
+	/* we have everything we need, start reading */
+	xlogreader_state = XLogReaderAllocate(XLogDumpReadPage, &private);
+	if (!xlogreader_state)
+		fatal_error("out of memory");
+
+	/* first find a valid recptr to start from */
+	first_record = XLogFindNextRecord(xlogreader_state, private.startptr);
+
+	if (first_record == InvalidXLogRecPtr)
+		fatal_error("could not find a valid record after %X/%X",
+					(uint32) (private.startptr >> 32),
+					(uint32) private.startptr);
+
+	/*
+	 * Display a message that we're skipping data if `from` wasn't a pointer to
+	 * the start of a record and also wasn't a pointer to the beginning of a
+	 * segment (e.g. we were used in file mode).
+	 */
+	if (first_record != private.startptr && (private.startptr % XLogSegSize) != 0)
+		printf("first record is after %X/%X, at %X/%X, skipping over %u bytes\n",
+			   (uint32) (private.startptr >> 32), (uint32) private.startptr,
+			   (uint32) (first_record >> 32), (uint32) first_record,
+			   (uint32) (first_record - private.startptr));
+
+	while ((record = XLogReadRecord(xlogreader_state, first_record, &errormsg)))
+	{
+		/* continue after the last record */
+		first_record = InvalidXLogRecPtr;
+		XLogDumpDisplayRecord(&config, xlogreader_state->ReadRecPtr, record);
+
+		/* check whether we printed enough */
+		if (config.stop_after_records > 0 &&
+			config.already_displayed_records >= config.stop_after_records)
+			break;
+	}
+
+	if (errormsg)
+		fatal_error("error in WAL record at %X/%X: %s\n",
+					(uint32) (xlogreader_state->ReadRecPtr >> 32),
+					(uint32) xlogreader_state->ReadRecPtr,
+					errormsg);
+
+	XLogReaderFree(xlogreader_state);
+
+	return EXIT_SUCCESS;
+
+bad_argument:
+	fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
+	return EXIT_FAILURE;
+}