Hi,
I will work out this one with postgres -C and come back till the next
commitfest. I found that something similar is already used in pg_ctl
and there is a mechanism for finding valid executables in exec.c. So
it does not seem to be a big deal at the first sight.
I have reworked the patch, please find new version attached. It is 3
times as smaller than the previous one and now touches pg_rewind's code
only. Tests are also slightly refactored in order to remove duplicated
code. Execution of postgres -C is used for restore_command retrieval (if
-r is passed) as being suggested. Otherwise everything works as before.
Andres, Alvaro does it make sense now?
Regards
--
Alexey Kondratov
Postgres Professional https://www.postgrespro.com
Russian Postgres Company
>From 4c8f5c228e089e7e72835ae5c409a5bc8425ab15 Mon Sep 17 00:00:00 2001
From: Alexey Kondratov <kondratov.alek...@gmail.com>
Date: Tue, 19 Feb 2019 19:14:53 +0300
Subject: [PATCH v4] pg_rewind: options to use restore_command from command
line or cluster config
---
doc/src/sgml/ref/pg_rewind.sgml | 30 ++++-
src/bin/pg_rewind/parsexlog.c | 161 +++++++++++++++++++++++++-
src/bin/pg_rewind/pg_rewind.c | 98 +++++++++++++++-
src/bin/pg_rewind/pg_rewind.h | 7 +-
src/bin/pg_rewind/t/001_basic.pl | 4 +-
src/bin/pg_rewind/t/002_databases.pl | 4 +-
src/bin/pg_rewind/t/003_extrafiles.pl | 4 +-
src/bin/pg_rewind/t/RewindTest.pm | 84 +++++++++++++-
8 files changed, 372 insertions(+), 20 deletions(-)
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 53a64ee29e..0c2441afa7 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -67,8 +67,10 @@ PostgreSQL documentation
ancestor. In the typical failover scenario where the target cluster was
shut down soon after the divergence, this is not a problem, but if the
target cluster ran for a long time after the divergence, the old WAL
- files might no longer be present. In that case, they can be manually
- copied from the WAL archive to the <filename>pg_wal</filename> directory, or
+ files might no longer be present. In that case, they can be automatically
+ copied by <application>pg_rewind</application> from the WAL archive to the
+ <filename>pg_wal</filename> directory if either <literal>-r</literal> or
+ <literal>-R</literal> option is specified, or
fetched on startup by configuring <xref linkend="guc-primary-conninfo"/> or
<xref linkend="guc-restore-command"/>. The use of
<application>pg_rewind</application> is not limited to failover, e.g. a standby
@@ -200,6 +202,30 @@ PostgreSQL documentation
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>-r</option></term>
+ <term><option>--use-postgresql-conf</option></term>
+ <listitem>
+ <para>
+ Use restore_command in the <filename>postgresql.conf</filename> to
+ retreive missing in the target <filename>pg_wal</filename> directory
+ WAL files from the WAL archive.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-R <replaceable class="parameter">restore_command</replaceable></option></term>
+ <term><option>--restore-command=<replaceable class="parameter">restore_command</replaceable></option></term>
+ <listitem>
+ <para>
+ Specifies the restore_command to use for retrieval of the missing
+ in the target <filename>pg_wal</filename> directory WAL files from
+ the WAL archive.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><option>--debug</option></term>
<listitem>
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index e19c265cbb..5978ec9b99 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -12,6 +12,7 @@
#include "postgres_fe.h"
#include <unistd.h>
+#include <sys/stat.h>
#include "pg_rewind.h"
#include "filemap.h"
@@ -45,6 +46,7 @@ static char xlogfpath[MAXPGPATH];
typedef struct XLogPageReadPrivate
{
const char *datadir;
+ const char *restoreCommand;
int tliIndex;
} XLogPageReadPrivate;
@@ -53,6 +55,9 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
TimeLineID *pageTLI);
+static int RestoreArchivedWAL(const char *path, const char *xlogfname,
+ off_t expectedSize, const char *restoreCommand);
+
/*
* Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
* index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
@@ -60,7 +65,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
*/
void
extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
- XLogRecPtr endpoint)
+ XLogRecPtr endpoint, const char *restore_command)
{
XLogRecord *record;
XLogReaderState *xlogreader;
@@ -69,6 +74,7 @@ extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
private.datadir = datadir;
private.tliIndex = tliIndex;
+ private.restoreCommand = restore_command;
xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
&private);
if (xlogreader == NULL)
@@ -156,7 +162,7 @@ readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
void
findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
- XLogRecPtr *lastchkptredo)
+ XLogRecPtr *lastchkptredo, const char *restoreCommand)
{
/* Walk backwards, starting from the given record */
XLogRecord *record;
@@ -181,6 +187,7 @@ findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
private.datadir = datadir;
private.tliIndex = tliIndex;
+ private.restoreCommand = restoreCommand;
xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
&private);
if (xlogreader == NULL)
@@ -291,9 +298,30 @@ SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
if (xlogreadfd < 0)
{
- printf(_("could not open file \"%s\": %s\n"), xlogfpath,
- strerror(errno));
- return -1;
+ /*
+ * If we have no restore_command to execute, then exit.
+ */
+ if (private->restoreCommand == NULL)
+ {
+ printf(_("could not open file \"%s\": %s\n"), xlogfpath,
+ strerror(errno));
+ return -1;
+ }
+
+ /*
+ * Since we have restore_command to execute, then try to retreive
+ * missing WAL file from the archive.
+ */
+ xlogreadfd = RestoreArchivedWAL(private->datadir,
+ xlogfname,
+ WalSegSz,
+ private->restoreCommand);
+
+ if (xlogreadfd < 0)
+ return -1;
+ else
+ pg_log(PG_DEBUG, "using restored from archive version of file \"%s\"\n",
+ xlogfpath);
}
}
@@ -409,3 +437,126 @@ extractPageInfo(XLogReaderState *record)
process_block_change(forknum, rnode, blkno);
}
}
+
+/*
+ * Attempt to retrieve the specified file from off-line archival storage.
+ * If successful return a file descriptor of restored WAL file, else
+ * return -1.
+ *
+ * For fixed-size files, the caller may pass the expected size as an
+ * additional crosscheck on successful recovery. If the file size is not
+ * known, set expectedSize = 0.
+ *
+ * This is a simplified and adapted to frontend version of
+ * RestoreArchivedFile function from transam/xlogarchive.c
+ */
+static int
+RestoreArchivedWAL(const char *path, const char *xlogfname,
+ off_t expectedSize, const char *restoreCommand)
+{
+ char xlogpath[MAXPGPATH],
+ xlogRestoreCmd[MAXPGPATH],
+ *dp,
+ *endp;
+ const char *sp;
+ int rc,
+ xlogfd;
+ struct stat stat_buf;
+
+ snprintf(xlogpath, MAXPGPATH, "%s/" XLOGDIR "/%s", path, xlogfname);
+
+ /*
+ * Construct the command to be executed.
+ */
+ dp = xlogRestoreCmd;
+ endp = xlogRestoreCmd + MAXPGPATH - 1;
+ *endp = '\0';
+
+ for (sp = restoreCommand; *sp; sp++)
+ {
+ if (*sp == '%')
+ {
+ switch (sp[1])
+ {
+ case 'p':
+ /* %p: relative path of target file */
+ sp++;
+ StrNCpy(dp, xlogpath, endp - dp);
+ make_native_path(dp);
+ dp += strlen(dp);
+ break;
+ case 'f':
+ /* %f: filename of desired file */
+ sp++;
+ StrNCpy(dp, xlogfname, endp - dp);
+ dp += strlen(dp);
+ break;
+ case 'r':
+ /* %r: filename of last restartpoint */
+ pg_fatal("restore_command with %%r cannot be used during rewind process.\n");
+ break;
+ case '%':
+ /* convert %% to a single % */
+ sp++;
+ if (dp < endp)
+ *dp++ = *sp;
+ break;
+ default:
+ /* otherwise treat the % as not special */
+ if (dp < endp)
+ *dp++ = *sp;
+ break;
+ }
+ }
+ else
+ {
+ if (dp < endp)
+ *dp++ = *sp;
+ }
+ }
+ *dp = '\0';
+
+ /*
+ * Execute restore_command, which should copy
+ * the missing WAL file from archival storage.
+ */
+ rc = system(xlogRestoreCmd);
+
+ if (rc == 0)
+ {
+ /*
+ * Command apparently succeeded, but let's make sure the file is
+ * really there now and has the correct size.
+ */
+ if (stat(xlogpath, &stat_buf) == 0)
+ {
+ if (expectedSize > 0 && stat_buf.st_size != expectedSize)
+ {
+ printf(_("archive file \"%s\" has wrong size: %lu instead of %lu, %s"),
+ xlogfname, (unsigned long) stat_buf.st_size,
+ (unsigned long) expectedSize, strerror(errno));
+ }
+ else
+ {
+ xlogfd = open(xlogpath, O_RDONLY | PG_BINARY, 0);
+
+ if (xlogfd < 0)
+ printf(_("could not open restored from archive file \"%s\": %s\n"),
+ xlogpath, strerror(errno));
+ else
+ return xlogfd;
+ }
+ }
+ else
+ {
+ /* Stat failed */
+ printf(_("could not stat file \"%s\": %s"),
+ xlogpath, strerror(errno));
+ }
+ }
+
+ printf(_("could not restore file \"%s\" from archive: %s\n"),
+ xlogfname, strerror(errno));
+
+ return -1;
+}
diff --git a/src/bin/pg_rewind/pg_rewind.c b/src/bin/pg_rewind/pg_rewind.c
index 7ccde5c87f..9da578ec42 100644
--- a/src/bin/pg_rewind/pg_rewind.c
+++ b/src/bin/pg_rewind/pg_rewind.c
@@ -30,6 +30,8 @@
#include "getopt_long.h"
#include "storage/bufpage.h"
+#define MAX_RESTORE_COMMAND 1024
+
static void usage(const char *progname);
static void createBackupLabel(XLogRecPtr startpoint, TimeLineID starttli,
@@ -52,11 +54,13 @@ int WalSegSz;
char *datadir_target = NULL;
char *datadir_source = NULL;
char *connstr_source = NULL;
+char *restore_command = NULL;
bool debug = false;
bool showprogress = false;
bool dry_run = false;
bool do_sync = true;
+bool restore_wals = false;
/* Target history */
TimeLineHistoryEntry *targetHistory;
@@ -75,6 +79,9 @@ usage(const char *progname)
printf(_(" -N, --no-sync do not wait for changes to be written\n"));
printf(_(" safely to disk\n"));
printf(_(" -P, --progress write progress messages\n"));
+ printf(_(" -r, --use-postgresql-conf use restore_command in the postgresql.conf to\n"));
+ printf(_(" retreive WALs from archive\n"));
+ printf(_(" -R, --restore-command=COMMAND restore_command\n"));
printf(_(" --debug write a lot of debug messages\n"));
printf(_(" -V, --version output version information, then exit\n"));
printf(_(" -?, --help show this help, then exit\n"));
@@ -94,6 +101,8 @@ main(int argc, char **argv)
{"dry-run", no_argument, NULL, 'n'},
{"no-sync", no_argument, NULL, 'N'},
{"progress", no_argument, NULL, 'P'},
+ {"use-postgresql-conf", no_argument, NULL, 'r'},
+ {"restore-command", required_argument, NULL, 'R'},
{"debug", no_argument, NULL, 3},
{NULL, 0, NULL, 0}
};
@@ -129,7 +138,7 @@ main(int argc, char **argv)
}
}
- while ((c = getopt_long(argc, argv, "D:nNP", long_options, &option_index)) != -1)
+ while ((c = getopt_long(argc, argv, "D:nNPR:r", long_options, &option_index)) != -1)
{
switch (c)
{
@@ -141,6 +150,10 @@ main(int argc, char **argv)
showprogress = true;
break;
+ case 'r':
+ restore_wals = true;
+ break;
+
case 'n':
dry_run = true;
break;
@@ -157,6 +170,10 @@ main(int argc, char **argv)
datadir_target = pg_strdup(optarg);
break;
+ case 'R':
+ restore_command = pg_strdup(optarg);
+ break;
+
case 1: /* --source-pgdata */
datadir_source = pg_strdup(optarg);
break;
@@ -223,6 +240,78 @@ main(int argc, char **argv)
umask(pg_mode_mask);
+ if (restore_command != NULL)
+ {
+ if (restore_wals)
+ {
+ fprintf(stderr, _("%s: conflicting options: both -r and -R are specified\n"),
+ progname);
+ fprintf(stderr, _("You must run %s with either -r/--use-postgresql-conf "
+ "or -R/--restore-command.\n"), progname);
+ exit(1);
+ }
+
+ pg_log(PG_DEBUG, "using command line restore_command=\'%s\'.\n", restore_command);
+ }
+ else if (restore_wals)
+ {
+ int rc;
+ char postgres_exec_path[MAXPGPATH],
+ postgres_cmd[MAXPGPATH],
+ cmd_output[MAX_RESTORE_COMMAND];
+ FILE *output_fp;
+
+ /* Find postgres executable. */
+ rc = find_other_exec(argv[0], "postgres",
+ PG_BACKEND_VERSIONSTR,
+ postgres_exec_path);
+
+ if (rc < 0)
+ {
+ char full_path[MAXPGPATH];
+
+ if (find_my_exec(argv[0], full_path) < 0)
+ strlcpy(full_path, progname, sizeof(full_path));
+
+ if (rc == -1)
+ fprintf(stderr,
+ _("the program \"postgres\" is needed by %s "
+ "but was not found in the\n"
+ "same directory as \"%s\".\n"
+ "Check your installation.\n"),
+ progname, full_path);
+ else
+ fprintf(stderr,
+ _("the program \"postgres\" was found by \"%s\"\n"
+ "but was not the same version as %s.\n"
+ "Check your installation.\n"),
+ full_path, progname);
+ exit(1);
+ }
+
+ /* Build a command to execute for restore_command GUC retrieval if set. */
+ snprintf(postgres_cmd, sizeof(postgres_cmd), "%s -D %s -C restore_command",
+ postgres_exec_path, datadir_target);
+
+ if ((output_fp = popen(postgres_cmd, "r")) == NULL ||
+ fgets(cmd_output, sizeof(cmd_output), output_fp) == NULL)
+ pg_fatal("could not get restore_command using %s: %s\n",
+ postgres_cmd, strerror(errno));
+
+ pclose(output_fp);
+
+ /* Remove trailing newline */
+ if (strchr(cmd_output, '\n') != NULL)
+ *strchr(cmd_output, '\n') = '\0';
+
+ if (!strcmp(cmd_output, ""))
+ pg_fatal("restore_command is not set on the target cluster\n");
+
+ restore_command = pg_strdup(cmd_output);
+
+ pg_log(PG_DEBUG, "using config variable restore_command=\'%s\'.\n", restore_command);
+ }
+
/* Connect to remote server */
if (connstr_source)
libpqConnect(connstr_source);
@@ -294,9 +383,8 @@ main(int argc, char **argv)
exit(0);
}
- findLastCheckpoint(datadir_target, divergerec,
- lastcommontliIndex,
- &chkptrec, &chkpttli, &chkptredo);
+ findLastCheckpoint(datadir_target, divergerec, lastcommontliIndex,
+ &chkptrec, &chkpttli, &chkptredo, restore_command);
printf(_("rewinding from last common checkpoint at %X/%X on timeline %u\n"),
(uint32) (chkptrec >> 32), (uint32) chkptrec,
chkpttli);
@@ -319,7 +407,7 @@ main(int argc, char **argv)
*/
pg_log(PG_PROGRESS, "reading WAL in target\n");
extractPageMap(datadir_target, chkptrec, lastcommontliIndex,
- ControlFile_target.checkPoint);
+ ControlFile_target.checkPoint, restore_command);
filemap_finalize();
if (showprogress)
diff --git a/src/bin/pg_rewind/pg_rewind.h b/src/bin/pg_rewind/pg_rewind.h
index 83b2898b8b..08a753475c 100644
--- a/src/bin/pg_rewind/pg_rewind.h
+++ b/src/bin/pg_rewind/pg_rewind.h
@@ -32,11 +32,10 @@ extern int targetNentries;
/* in parsexlog.c */
extern void extractPageMap(const char *datadir, XLogRecPtr startpoint,
- int tliIndex, XLogRecPtr endpoint);
+ int tliIndex, XLogRecPtr endpoint, const char *restoreCommand);
extern void findLastCheckpoint(const char *datadir, XLogRecPtr searchptr,
- int tliIndex,
- XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
- XLogRecPtr *lastchkptredo);
+ int tliIndex, XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
+ XLogRecPtr *lastchkptredo, const char *restoreCommand);
extern XLogRecPtr readOneRecord(const char *datadir, XLogRecPtr ptr,
int tliIndex);
diff --git a/src/bin/pg_rewind/t/001_basic.pl b/src/bin/pg_rewind/t/001_basic.pl
index 115192170e..8a6fa33016 100644
--- a/src/bin/pg_rewind/t/001_basic.pl
+++ b/src/bin/pg_rewind/t/001_basic.pl
@@ -1,7 +1,7 @@
use strict;
use warnings;
use TestLib;
-use Test::More tests => 10;
+use Test::More tests => 20;
use FindBin;
use lib $FindBin::RealBin;
@@ -106,5 +106,7 @@ in master, before promotion
# Run the test in both modes
run_test('local');
run_test('remote');
+run_test('archive');
+run_test('archive_conf');
exit(0);
diff --git a/src/bin/pg_rewind/t/002_databases.pl b/src/bin/pg_rewind/t/002_databases.pl
index 6dc05720a1..99ea821cfe 100644
--- a/src/bin/pg_rewind/t/002_databases.pl
+++ b/src/bin/pg_rewind/t/002_databases.pl
@@ -1,7 +1,7 @@
use strict;
use warnings;
use TestLib;
-use Test::More tests => 6;
+use Test::More tests => 12;
use FindBin;
use lib $FindBin::RealBin;
@@ -62,5 +62,7 @@ template1
# Run the test in both modes.
run_test('local');
run_test('remote');
+run_test('archive');
+run_test('archive_conf');
exit(0);
diff --git a/src/bin/pg_rewind/t/003_extrafiles.pl b/src/bin/pg_rewind/t/003_extrafiles.pl
index c4040bd562..24cec256de 100644
--- a/src/bin/pg_rewind/t/003_extrafiles.pl
+++ b/src/bin/pg_rewind/t/003_extrafiles.pl
@@ -3,7 +3,7 @@
use strict;
use warnings;
use TestLib;
-use Test::More tests => 4;
+use Test::More tests => 8;
use File::Find;
@@ -90,5 +90,7 @@ sub run_test
# Run the test in both modes.
run_test('local');
run_test('remote');
+run_test('archive');
+run_test('archive_conf');
exit(0);
diff --git a/src/bin/pg_rewind/t/RewindTest.pm b/src/bin/pg_rewind/t/RewindTest.pm
index 85cae7e47b..4560fe4430 100644
--- a/src/bin/pg_rewind/t/RewindTest.pm
+++ b/src/bin/pg_rewind/t/RewindTest.pm
@@ -39,7 +39,9 @@ use Carp;
use Config;
use Exporter 'import';
use File::Copy;
-use File::Path qw(rmtree);
+use File::Glob ':bsd_glob';
+use File::Path qw(remove_tree make_path);
+use File::Spec::Functions qw(catdir catfile);
use IPC::Run qw(run);
use PostgresNode;
use TestLib;
@@ -197,6 +199,38 @@ sub promote_standby
return;
}
+# Moves WAL files to the temporary location and returns restore_command
+# to get them back.
+sub move_wals
+{
+ my $tmp_dir = shift;
+ my $master_pgdata = shift;
+ my $wals_archive_dir = catdir($tmp_dir, "master_wals_archive");
+ my @wal_files = bsd_glob catfile($master_pgdata, "pg_wal", "0000000*");
+ my $restore_command;
+
+ remove_tree($wals_archive_dir);
+ make_path($wals_archive_dir) or die;
+
+ # Move all old master WAL files to the archive.
+ # Old master should be stopped at this point.
+ foreach my $wal_file (@wal_files)
+ {
+ move($wal_file, "$wals_archive_dir") or die;
+ }
+
+ if ($windows_os)
+ {
+ $restore_command = "copy $wals_archive_dir\\\%f \%p";
+ }
+ else
+ {
+ $restore_command = "cp $wals_archive_dir/\%f \%p";
+ }
+
+ return $restore_command;
+}
+
sub run_pg_rewind
{
my $test_mode = shift;
@@ -249,6 +283,54 @@ sub run_pg_rewind
],
'pg_rewind remote');
}
+ elsif ($test_mode eq "archive")
+ {
+
+ # Do rewind using a local pgdata as source and
+ # specified directory with target WALs archive.
+ my $restore_command = move_wals($tmp_folder, $master_pgdata);
+
+ # Stop the new master and be ready to perform the rewind.
+ $node_standby->stop;
+
+ command_ok(
+ [
+ 'pg_rewind',
+ "--debug",
+ "--source-pgdata=$standby_pgdata",
+ "--target-pgdata=$master_pgdata",
+ "--no-sync",
+ "--restore-command=$restore_command"
+ ],
+ 'pg_rewind archive');
+ }
+ elsif ($test_mode eq "archive_conf")
+ {
+
+ # Do rewind using a local pgdata as source and
+ # specified directory with target WALs archive.
+ my $master_conf_path = catfile($master_pgdata, 'postgresql.conf');
+ my $restore_command = move_wals($tmp_folder, $master_pgdata);
+
+ # Stop the new master and be ready to perform the rewind.
+ $node_standby->stop;
+
+ # Add restore_command to postgresql.conf of target cluster.
+ open(my $conf_fd, ">>", $master_conf_path) or die;
+ print $conf_fd "\nrestore_command='$restore_command'";
+ close $conf_fd;
+
+ command_ok(
+ [
+ 'pg_rewind',
+ "--debug",
+ "--source-pgdata=$standby_pgdata",
+ "--target-pgdata=$master_pgdata",
+ "--no-sync",
+ "-r"
+ ],
+ 'pg_rewind archive_conf');
+ }
else
{
base-commit: 41531e42d34f4aca117d343b5e40f3f757dec5fe
--
2.17.1
