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Implement "pg_ctl logrotate" command
Currently there are two ways to trigger log rotation in logging collector process: call pg_rotate_logfile() SQL-function or send SIGUSR1 signal directly to logging collector process. However, it's nice to have more suitable way for external tools to do that, which wouldn't require SQL connection or knowledge of logging collector pid. This commit implements triggering log rotation by "pg_ctl logrotate" command. Discussion: https://postgr.es/m/20180416.115435.28153375.horiguchi.kyotaro%40lab.ntt.co.jp Author: Kyotaro Horiguchi, Alexander Kuzmenkov, Alexander Korotkov
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8 files changed

+230
-19
lines changed

8 files changed

+230
-19
lines changed

‎doc/src/sgml/maintenance.sgml

Lines changed: 32 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -932,8 +932,8 @@ analyze threshold = analyze base threshold + analyze scale factor * number of tu
932932
program if you have one that you are already using with other
933933
server software. For example, the <application>rotatelogs</application>
934934
tool included in the <productname>Apache</productname> distribution
935-
can be used with <productname>PostgreSQL</productname>. To do this,
936-
just pipe the server's
935+
can be used with <productname>PostgreSQL</productname>. One way to
936+
do this is to pipe the server's
937937
<systemitem>stderr</systemitem> output to the desired program.
938938
If you start the server with
939939
<command>pg_ctl</command>, then <systemitem>stderr</systemitem>
@@ -945,6 +945,36 @@ pg_ctl start | rotatelogs /var/log/pgsql_log 86400
945945
</programlisting>
946946
</para>
947947

948+
<para>
949+
You can combine these approaches by setting up <application>logrotate</application>
950+
to collect log files produced by <productname>PostgreSQL</productname> built-in
951+
logging collector. In this case, the logging collector defines the names and
952+
location of the log files, while <application>logrotate</application>
953+
periodically archives these files. When initiating log rotation,
954+
<application>logrotate</application> must ensure that the application
955+
sends further output to the new file. This is commonly done with a
956+
<literal>postrotate</literal> script that sends a <literal>SIGHUP</literal>
957+
signal to the application, which then reopens the log file.
958+
In <productname>PostgreSQL</productname>, you can run <command>pg_ctl</command>
959+
with the <literal>logrotate</literal> option instead. When the server receives
960+
this command, the server either switches to a new log file or reopens the
961+
existing file, depending on the logging configuration
962+
(see <xref linkend="runtime-config-logging-where"/>).
963+
</para>
964+
965+
<note>
966+
<para>
967+
When using static log file names, the server might fail to reopen the log
968+
file if the max open file limit is reached or a file table overflow occurs.
969+
In this case, log messages are sent to the old log file until a
970+
successful log rotation. If <application>logrotate</application> is
971+
configured to compress the log file and delete it, the server may lose
972+
the messages logged in this timeframe. To avoid this issue, you can
973+
configure the logging collector to dynamically assign log file names
974+
and use a <literal>prerotate</literal> script to ignore open log files.
975+
</para>
976+
</note>
977+
948978
<para>
949979
Another production-grade approach to managing log output is to
950980
send it to <application>syslog</application> and let

‎doc/src/sgml/ref/pg_ctl-ref.sgml

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -97,6 +97,13 @@ PostgreSQL documentation
9797
<arg choice="opt"><option>-s</option></arg>
9898
</cmdsynopsis>
9999

100+
<cmdsynopsis>
101+
<command>pg_ctl</command>
102+
<arg choice="plain"><option>logrotate</option></arg>
103+
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
104+
<arg choice="opt"><option>-s</option></arg>
105+
</cmdsynopsis>
106+
100107
<cmdsynopsis>
101108
<command>pg_ctl</command>
102109
<arg choice="plain"><option>kill</option></arg>
@@ -226,6 +233,12 @@ PostgreSQL documentation
226233
and begin read-write operations.
227234
</para>
228235

236+
<para>
237+
<option>logrotate</option> mode rotates the server log file.
238+
For details on how to use this mode with external log rotation tools, see
239+
<xref linkend="logfile-maintenance"/>.
240+
</para>
241+
229242
<para>
230243
<option>kill</option> mode sends a signal to a specified process.
231244
This is primarily valuable on <productname>Microsoft Windows</productname>

‎src/backend/postmaster/postmaster.c

Lines changed: 14 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1268,6 +1268,9 @@ PostmasterMain(int argc, char *argv[])
12681268
*/
12691269
RemovePromoteSignalFiles();
12701270

1271+
/* Do the same for logrotate signal file */
1272+
RemoveLogrotateSignalFiles();
1273+
12711274
/* Remove any outdated file holding the current log filenames. */
12721275
if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
12731276
ereport(LOG,
@@ -5100,11 +5103,18 @@ sigusr1_handler(SIGNAL_ARGS)
51005103
signal_child(PgArchPID, SIGUSR1);
51015104
}
51025105

5103-
if (CheckPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE) &&
5104-
SysLoggerPID != 0)
5106+
/* Tell syslogger to rotate logfile if requested */
5107+
if (SysLoggerPID != 0)
51055108
{
5106-
/* Tell syslogger to rotate logfile */
5107-
signal_child(SysLoggerPID, SIGUSR1);
5109+
if (CheckLogrotateSignal())
5110+
{
5111+
signal_child(SysLoggerPID, SIGUSR1);
5112+
RemoveLogrotateSignalFiles();
5113+
}
5114+
else if (CheckPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE))
5115+
{
5116+
signal_child(SysLoggerPID, SIGUSR1);
5117+
}
51085118
}
51095119

51105120
if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER) &&

‎src/backend/postmaster/syslogger.c

Lines changed: 28 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,9 @@
5757
*/
5858
#define READ_BUF_SIZE (2 * PIPE_CHUNK_SIZE)
5959

60+
/* Log rotation signal file path, relative to $PGDATA */
61+
#define LOGROTATE_SIGNAL_FILE "logrotate"
62+
6063

6164
/*
6265
* GUC parameters. Logging_collector cannot be changed after postmaster
@@ -405,7 +408,7 @@ SysLoggerMain(int argc, char *argv[])
405408
{
406409
/*
407410
* Force rotation when both values are zero. It means the request
408-
* was sent by pg_rotate_logfile.
411+
* was sent by pg_rotate_logfile() or "pg_ctl logrotate".
409412
*/
410413
if (!time_based_rotation && size_rotation_for == 0)
411414
size_rotation_for = LOG_DESTINATION_STDERR | LOG_DESTINATION_CSVLOG;
@@ -1506,6 +1509,30 @@ update_metainfo_datafile(void)
15061509
* --------------------------------
15071510
*/
15081511

1512+
/*
1513+
* Check to see if a log rotation request has arrived. Should be
1514+
* called by postmaster after receiving SIGUSR1.
1515+
*/
1516+
bool
1517+
CheckLogrotateSignal(void)
1518+
{
1519+
struct stat stat_buf;
1520+
1521+
if (stat(LOGROTATE_SIGNAL_FILE, &stat_buf) == 0)
1522+
return true;
1523+
1524+
return false;
1525+
}
1526+
1527+
/*
1528+
* Remove the file signaling a log rotateion request.
1529+
*/
1530+
void
1531+
RemoveLogrotateSignalFiles(void)
1532+
{
1533+
unlink(LOGROTATE_SIGNAL_FILE);
1534+
}
1535+
15091536
/* SIGHUP: set flag to reload config file */
15101537
static void
15111538
sigHupHandler(SIGNAL_ARGS)

‎src/bin/pg_ctl/pg_ctl.c

Lines changed: 77 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -61,6 +61,7 @@ typedef enum
6161
RELOAD_COMMAND,
6262
STATUS_COMMAND,
6363
PROMOTE_COMMAND,
64+
LOGROTATE_COMMAND,
6465
KILL_COMMAND,
6566
REGISTER_COMMAND,
6667
UNREGISTER_COMMAND,
@@ -100,6 +101,7 @@ static char version_file[MAXPGPATH];
100101
static char pid_file[MAXPGPATH];
101102
static char backup_file[MAXPGPATH];
102103
static char promote_file[MAXPGPATH];
104+
static char logrotate_file[MAXPGPATH];
103105

104106
#ifdef WIN32
105107
static DWORD pgctl_start_type = SERVICE_AUTO_START;
@@ -125,6 +127,7 @@ static void do_restart(void);
125127
static void do_reload(void);
126128
static void do_status(void);
127129
static void do_promote(void);
130+
static void do_logrotate(void);
128131
static void do_kill(pgpid_t pid);
129132
static void print_msg(const char *msg);
130133
static void adjust_data_dir(void);
@@ -1171,6 +1174,62 @@ do_promote(void)
11711174
print_msg(_("server promoting\n"));
11721175
}
11731176

1177+
/*
1178+
* log rotate
1179+
*/
1180+
1181+
static void
1182+
do_logrotate(void)
1183+
{
1184+
FILE *logrotatefile;
1185+
pgpid_t pid;
1186+
1187+
pid = get_pgpid(false);
1188+
1189+
if (pid == 0) /* no pid file */
1190+
{
1191+
write_stderr(_("%s: PID file \"%s\" does not exist\n"), progname, pid_file);
1192+
write_stderr(_("Is server running?\n"));
1193+
exit(1);
1194+
}
1195+
else if (pid < 0) /* standalone backend, not postmaster */
1196+
{
1197+
pid = -pid;
1198+
write_stderr(_("%s: cannot rotate log file; "
1199+
"single-user server is running (PID: %ld)\n"),
1200+
progname, pid);
1201+
exit(1);
1202+
}
1203+
1204+
snprintf(logrotate_file, MAXPGPATH, "%s/logrotate", pg_data);
1205+
1206+
if ((logrotatefile = fopen(logrotate_file, "w")) == NULL)
1207+
{
1208+
write_stderr(_("%s: could not create log rotation signal file \"%s\": %s\n"),
1209+
progname, logrotate_file, strerror(errno));
1210+
exit(1);
1211+
}
1212+
if (fclose(logrotatefile))
1213+
{
1214+
write_stderr(_("%s: could not write log rotation signal file \"%s\": %s\n"),
1215+
progname, logrotate_file, strerror(errno));
1216+
exit(1);
1217+
}
1218+
1219+
sig = SIGUSR1;
1220+
if (kill((pid_t) pid, sig) != 0)
1221+
{
1222+
write_stderr(_("%s: could not send log rotation signal (PID: %ld): %s\n"),
1223+
progname, pid, strerror(errno));
1224+
if (unlink(logrotate_file) != 0)
1225+
write_stderr(_("%s: could not remove log rotation signal file \"%s\": %s\n"),
1226+
progname, logrotate_file, strerror(errno));
1227+
exit(1);
1228+
}
1229+
1230+
print_msg(_("server signaled to rotate log file\n"));
1231+
}
1232+
11741233

11751234
/*
11761235
* utility routines
@@ -1912,19 +1971,20 @@ do_help(void)
19121971
{
19131972
printf(_("%s is a utility to initialize, start, stop, or control a PostgreSQL server.\n\n"), progname);
19141973
printf(_("Usage:\n"));
1915-
printf(_(" %s init[db] [-D DATADIR] [-s] [-o OPTIONS]\n"), progname);
1916-
printf(_(" %s start [-D DATADIR] [-l FILENAME] [-W] [-t SECS] [-s]\n"
1917-
" [-o OPTIONS] [-p PATH] [-c]\n"), progname);
1918-
printf(_(" %s stop [-D DATADIR] [-m SHUTDOWN-MODE] [-W] [-t SECS] [-s]\n"), progname);
1919-
printf(_(" %s restart [-D DATADIR] [-m SHUTDOWN-MODE] [-W] [-t SECS] [-s]\n"
1920-
" [-o OPTIONS] [-c]\n"), progname);
1921-
printf(_(" %s reload [-D DATADIR] [-s]\n"), progname);
1922-
printf(_(" %s status [-D DATADIR]\n"), progname);
1923-
printf(_(" %s promote [-D DATADIR] [-W] [-t SECS] [-s]\n"), progname);
1924-
printf(_(" %s kill SIGNALNAME PID\n"), progname);
1974+
printf(_(" %s init[db] [-D DATADIR] [-s] [-o OPTIONS]\n"), progname);
1975+
printf(_(" %s start [-D DATADIR] [-l FILENAME] [-W] [-t SECS] [-s]\n"
1976+
" [-o OPTIONS] [-p PATH] [-c]\n"), progname);
1977+
printf(_(" %s stop [-D DATADIR] [-m SHUTDOWN-MODE] [-W] [-t SECS] [-s]\n"), progname);
1978+
printf(_(" %s restart [-D DATADIR] [-m SHUTDOWN-MODE] [-W] [-t SECS] [-s]\n"
1979+
" [-o OPTIONS] [-c]\n"), progname);
1980+
printf(_(" %s reload [-D DATADIR] [-s]\n"), progname);
1981+
printf(_(" %s status [-D DATADIR]\n"), progname);
1982+
printf(_(" %s promote [-D DATADIR] [-W] [-t SECS] [-s]\n"), progname);
1983+
printf(_(" %s logrotate [-D DATADIR] [-s]\n"), progname);
1984+
printf(_(" %s kill SIGNALNAME PID\n"), progname);
19251985
#ifdef WIN32
1926-
printf(_(" %s register [-D DATADIR] [-N SERVICENAME] [-U USERNAME] [-P PASSWORD]\n"
1927-
" [-S START-TYPE] [-e SOURCE] [-W] [-t SECS] [-s] [-o OPTIONS]\n"), progname);
1986+
printf(_(" %s register [-D DATADIR] [-N SERVICENAME] [-U USERNAME] [-P PASSWORD]\n"
1987+
" [-S START-TYPE] [-e SOURCE] [-W] [-t SECS] [-s] [-o OPTIONS]\n"), progname);
19281988
printf(_(" %s unregister [-N SERVICENAME]\n"), progname);
19291989
#endif
19301990

@@ -2337,6 +2397,8 @@ main(int argc, char **argv)
23372397
ctl_command = STATUS_COMMAND;
23382398
else if (strcmp(argv[optind], "promote") == 0)
23392399
ctl_command = PROMOTE_COMMAND;
2400+
else if (strcmp(argv[optind], "logrotate") == 0)
2401+
ctl_command = LOGROTATE_COMMAND;
23402402
else if (strcmp(argv[optind], "kill") == 0)
23412403
{
23422404
if (argc - optind < 3)
@@ -2443,6 +2505,9 @@ main(int argc, char **argv)
24432505
case PROMOTE_COMMAND:
24442506
do_promote();
24452507
break;
2508+
case LOGROTATE_COMMAND:
2509+
do_logrotate();
2510+
break;
24462511
case KILL_COMMAND:
24472512
do_kill(killproc);
24482513
break;

‎src/bin/pg_ctl/t/004_logrotate.pl

Lines changed: 42 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,42 @@
1+
use strict;
2+
use warnings;
3+
4+
use PostgresNode;
5+
use TestLib;
6+
use Test::More tests => 1;
7+
use Time::HiRes qw(usleep);
8+
9+
my $tempdir = TestLib::tempdir;
10+
11+
my $node = get_new_node('primary');
12+
$node->init(allows_streaming => 1);
13+
$node->append_conf(
14+
'postgresql.conf', qq(
15+
logging_collector = on
16+
log_directory = 'log'
17+
log_filename = 'postgresql.log'
18+
));
19+
20+
$node->start();
21+
22+
# Rename log file and rotate log. Then log file should appear again.
23+
24+
my $logfile = $node->data_dir . '/log/postgresql.log';
25+
my $old_logfile = $node->data_dir . '/log/postgresql.old';
26+
rename($logfile, $old_logfile);
27+
28+
$node->logrotate();
29+
30+
# pg_ctl logrotate doesn't wait until rotation request being completed. So
31+
# we have to wait some time until log file appears.
32+
my $attempts = 0;
33+
my $max_attempts = 180 * 10;
34+
while (not -e $logfile and $attempts < $max_attempts)
35+
{
36+
usleep(100_000);
37+
$attempts++;
38+
}
39+
40+
ok(-e $logfile, "log file exists");
41+
42+
$node->stop();

‎src/include/postmaster/syslogger.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -87,6 +87,9 @@ extern void write_syslogger_file(const char *buffer, int count, int dest);
8787
extern void SysLoggerMain(int argc, char *argv[]) pg_attribute_noreturn();
8888
#endif
8989

90+
extern bool CheckLogrotateSignal(void);
91+
extern void RemoveLogrotateSignalFiles(void);
92+
9093
/*
9194
* Name of files saving meta-data information about the log
9295
* files currently in use by the syslogger

‎src/test/perl/PostgresNode.pm

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -804,6 +804,27 @@ sub promote
804804
return;
805805
}
806806

807+
=pod
808+
809+
=item $node->logrotate()
810+
811+
Wrapper for pg_ctl logrotate
812+
813+
=cut
814+
815+
sub logrotate
816+
{
817+
my ($self) = @_;
818+
my $port = $self->port;
819+
my $pgdata = $self->data_dir;
820+
my $logfile = $self->logfile;
821+
my $name = $self->name;
822+
print "### Rotating log in node \"$name\"\n";
823+
TestLib::system_or_bail('pg_ctl', '-D', $pgdata, '-l', $logfile,
824+
'logrotate');
825+
return;
826+
}
827+
807828
# Internal routine to enable streaming replication on a standby node.
808829
sub enable_streaming
809830
{

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