From f2c52eeba919a1b191f60445001371bd7c53aaa9 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 2 Dec 2021 13:52:16 +0900
Subject: [PATCH] pg_waldump: Emit stats summary when interrupted by SIGINT
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Previously, pg_waldump would not display its statistics summary if it
got interrupted by SIGINT (or say a simple Ctrl+C). It gains with this
commit a signal handler for SIGINT, trapping the signal to exit at the
earliest convenience to allow a display of the stats summary before
exiting. This makes the reports more interactive, similarly to strace
-c.
This new behavior makes the combination of the options --stats and
--follow much more useful, so as the user will get a report for any
invocation of pg_waldump in such a case. Information about the LSN
range of the stats computed is added as a header to the report
displayed.
This implementation comes from a suggestion by Álvaro Herrera and
myself, following a complaint by the author of this patch about --stats
and --follow not being useful together originally.
As documented, this is not supported on Windows, though its support
would be possible by catching the terminal events associated to Ctrl+C,
for example (this may require a more centralized implementation, as
other tools could benefit from a common API).
Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACUUx3PcK2z9h0_m7vehreZAUbcmOky9WSEpe8TofhV=PQ@mail.gmail.com
---
doc/src/sgml/ref/pg_waldump.sgml | 9 ++++++
src/bin/pg_waldump/pg_waldump.c | 48 ++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
diff --git a/doc/src/sgml/ref/pg_waldump.sgml b/doc/src/sgml/ref/pg_waldump.sgml
index 432254d2d5..5735a161ce 100644
--- a/doc/src/sgml/ref/pg_waldump.sgml
+++ b/doc/src/sgml/ref/pg_waldump.sgml
@@ -202,6 +202,15 @@ PostgreSQL documentation
full-page images) instead of individual records. Optionally
generate statistics per-record instead of per-rmgr.
</para>
+
+ <para>
+ If <application>pg_waldump</application> is terminated by signal
+ <systemitem>SIGINT</systemitem>
+ (<keycombo action="simul"><keycap>Control</keycap><keycap>C</keycap></keycombo>,
+ the summary of the statistics computed is displayed up to the
+ termination point. This operation is not supported on
+ <productname>Windows</productname>.
+ </para>
</listitem>
</varlistentry>
diff --git a/src/bin/pg_waldump/pg_waldump.c b/src/bin/pg_waldump/pg_waldump.c
index 4690e0f515..f66b5a8dba 100644
--- a/src/bin/pg_waldump/pg_waldump.c
+++ b/src/bin/pg_waldump/pg_waldump.c
@@ -13,6 +13,7 @@
#include "postgres.h"
#include <dirent.h>
+#include <signal.h>
#include <sys/stat.h>
#include <unistd.h>
@@ -28,6 +29,7 @@
static const char *progname;
static int WalSegSz;
+static volatile sig_atomic_t time_to_stop = false;
typedef struct XLogDumpPrivate
{
@@ -67,12 +69,27 @@ typedef struct Stats
typedef struct XLogDumpStats
{
uint64 count;
+ XLogRecPtr startptr;
+ XLogRecPtr endptr;
Stats rmgr_stats[RM_NEXT_ID];
Stats record_stats[RM_NEXT_ID][MAX_XLINFO_TYPES];
} XLogDumpStats;
#define fatal_error(...) do { pg_log_fatal(__VA_ARGS__); exit(EXIT_FAILURE); } while(0)
+/*
+ * When sigint is called, just tell the system to exit at the next possible
+ * moment.
+ */
+#ifndef WIN32
+
+static void
+sigint_handler(int signum)
+{
+ time_to_stop = true;
+}
+#endif
+
static void
print_rmgr_list(void)
{
@@ -632,6 +649,12 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
double rec_len_pct,
fpi_len_pct;
+ /*
+ * Leave if no stats have been computed yet, as tracked by the end LSN.
+ */
+ if (XLogRecPtrIsInvalid(stats->endptr))
+ return;
+
/*
* Each row shows its percentages of the total, so make a first pass to
* calculate column totals.
@@ -645,6 +668,9 @@ XLogDumpDisplayStats(XLogDumpConfig *config, XLogDumpStats *stats)
}
total_len = total_rec_len + total_fpi_len;
+ printf("WAL statistics between %X/%X and %X/%X:\n",
+ LSN_FORMAT_ARGS(stats->startptr), LSN_FORMAT_ARGS(stats->endptr));
+
/*
* 27 is strlen("Transaction/COMMIT_PREPARED"), 20 is strlen(2^64), 8 is
* strlen("(100.00%)")
@@ -794,6 +820,10 @@ main(int argc, char **argv)
int option;
int optindex = 0;
+#ifndef WIN32
+ pqsignal(SIGINT, sigint_handler);
+#endif
+
pg_logging_init(argv[0]);
set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_waldump"));
progname = get_progname(argv[0]);
@@ -833,6 +863,9 @@ main(int argc, char **argv)
config.stats = false;
config.stats_per_record = false;
+ stats.startptr = InvalidXLogRecPtr;
+ stats.endptr = InvalidXLogRecPtr;
+
if (argc <= 1)
{
pg_log_error("no arguments specified");
@@ -1084,8 +1117,17 @@ main(int argc, char **argv)
LSN_FORMAT_ARGS(first_record),
(uint32) (first_record - private.startptr));
+ if (config.stats == true && !config.quiet)
+ stats.startptr = first_record;
+
for (;;)
{
+ if (time_to_stop)
+ {
+ /* We've been Ctrl-C'ed, so leave */
+ break;
+ }
+
/* try to read the next record */
record = XLogReadRecord(xlogreader_state, &errormsg);
if (!record)
@@ -1112,7 +1154,10 @@ main(int argc, char **argv)
if (!config.quiet)
{
if (config.stats == true)
+ {
XLogDumpCountRecord(&config, &stats, xlogreader_state);
+ stats.endptr = xlogreader_state->EndRecPtr;
+ }
else
XLogDumpDisplayRecord(&config, xlogreader_state);
}
@@ -1127,6 +1172,9 @@ main(int argc, char **argv)
if (config.stats == true && !config.quiet)
XLogDumpDisplayStats(&config, &stats);
+ if (time_to_stop)
+ exit(0);
+
if (errormsg)
fatal_error("error in WAL record at %X/%X: %s",
LSN_FORMAT_ARGS(xlogreader_state->ReadRecPtr),