V3-0001-parameter-max_log_size-to-truncate-logs.patch

From 9439eb1c5c194d38a6aa388d8d8ca34350ae300f Mon Sep 17 00:00:00 2001
From: diphantxm <diphantxm@yandex-team.ru>
Date: Thu, 28 Nov 2024 21:24:59 +0300
Subject: [PATCH] parameter max_log_size to truncate logs

There is no need to log the entire query, because it may be large and take lots of space on disk. Parameter max_log_size set the maximum length for logged query. Everything beyond that length is truncated. Value 0 disables the parameter.
---
 doc/src/sgml/config.sgml                      | 15 ++++++++
 src/backend/tcop/postgres.c                   | 10 ++++-
 src/backend/utils/error/elog.c                | 38 +++++++++++++++++++
 src/backend/utils/misc/guc_tables.c           | 11 ++++++
 src/backend/utils/misc/postgresql.conf.sample |  2 +
 src/bin/pg_ctl/t/004_logrotate.pl             | 15 ++++++++
 src/include/utils/elog.h                      |  2 +
 7 files changed, 91 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 76ab72db96..5110b61ba5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7913,6 +7913,21 @@ log_line_prefix = '%m [%p] %q%u@%d/%a '
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-max-log-size" xreflabel="max_log_size">
+      <term><varname>max_log_size</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>max_log_size</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        If greater than zero, each query logged is truncated to this many bytes.
+        Zero disables the setting.
+        Default value is 5kB.
+       </para>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
     </sect2>
      <sect2 id="runtime-config-logging-csvlog">
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 4b985bd056..549be13e5b 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -70,6 +70,7 @@
 #include "tcop/pquery.h"
 #include "tcop/tcopprot.h"
 #include "tcop/utility.h"
+#include "utils/elog.h"
 #include "utils/guc_hooks.h"
 #include "utils/injection_point.h"
 #include "utils/lsyscache.h"
@@ -1029,11 +1030,14 @@ exec_simple_query(const char *query_string)
 	bool		was_logged = false;
 	bool		use_implicit_block;
 	char		msec_str[32];
+	char* 		query_log;
 
 	/*
 	 * Report query to various monitoring facilities.
 	 */
 	debug_query_string = query_string;
+	bool copied = false;
+	query_log = build_query_log(query_string, &copied);
 
 	pgstat_report_activity(STATE_RUNNING, query_string);
 
@@ -1078,7 +1082,7 @@ exec_simple_query(const char *query_string)
 	if (check_log_statement(parsetree_list))
 	{
 		ereport(LOG,
-				(errmsg("statement: %s", query_string),
+				(errmsg("statement: %s", query_log),
 				 errhidestmt(true),
 				 errdetail_execute(parsetree_list)));
 		was_logged = true;
@@ -1377,7 +1381,7 @@ exec_simple_query(const char *query_string)
 		case 2:
 			ereport(LOG,
 					(errmsg("duration: %s ms  statement: %s",
-							msec_str, query_string),
+							msec_str, query_log),
 					 errhidestmt(true),
 					 errdetail_execute(parsetree_list)));
 			break;
@@ -1388,6 +1392,8 @@ exec_simple_query(const char *query_string)
 
 	TRACE_POSTGRESQL_QUERY_DONE(query_string);
 
+	if (query_log && copied)
+		pfree(query_log);
 	debug_query_string = NULL;
 }
 
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 289059435a..aa9712ba64 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -111,6 +111,7 @@ int			Log_destination = LOG_DESTINATION_STDERR;
 char	   *Log_destination_string = NULL;
 bool		syslog_sequence_numbers = true;
 bool		syslog_split_messages = true;
+int			max_log_size = 0;
 
 /* Processed form of backtrace_functions GUC */
 static char *backtrace_function_list;
@@ -1693,6 +1694,10 @@ EmitErrorReport(void)
 	CHECK_STACK_DEPTH();
 	oldcontext = MemoryContextSwitchTo(edata->assoc_context);
 
+	const char* old_query_string = debug_query_string;
+	bool copied = false;
+	debug_query_string = build_query_log(debug_query_string, &copied);
+
 	/*
 	 * Reset the formatted timestamp fields before emitting any logs.  This
 	 * includes all the log destinations and emit_log_hook, as the latter
@@ -1733,6 +1738,12 @@ EmitErrorReport(void)
 
 	MemoryContextSwitchTo(oldcontext);
 	recursion_depth--;
+
+	if (debug_query_string && copied)
+	{
+		pfree(debug_query_string);
+		debug_query_string = old_query_string;
+	}
 }
 
 /*
@@ -3773,3 +3784,30 @@ write_stderr(const char *fmt,...)
 #endif
 	va_end(ap);
 }
+
+/*
+ *	Apply truncation to build query that will be logged.
+ *
+ *	If query needs to be truncated, copied will be set to true 
+ *	and returned string must be freed
+*/
+char*
+build_query_log(const char* query, bool *copied)
+{
+	*copied = false;
+	if (!query)
+		return NULL;
+
+	size_t query_len = strlen(query);
+	if (max_log_size == 0 || query_len < max_log_size)
+	{
+		return query;
+	}
+
+	*copied = true;
+	size_t query_log_len = pg_mbcliplen(query, query_len, max_log_size);
+	char* query_log = (char*)palloc(query_log_len+1);
+	memcpy(query_log, query, query_log_len);
+	query_log[query_log_len] = '\0';
+	return query_log;
+}
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 9845abd693..64f21377ad 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -3724,6 +3724,17 @@ struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"max_log_size", PGC_SUSET, LOGGING_WHAT,
+			gettext_noop("Sets max size in bytes of logged statement."),
+			NULL
+		},
+		&max_log_size,
+		5 * (1024 * 1024),
+		0, INT_MAX,
+		NULL, NULL, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 407cd1e08c..44971cecc6 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -617,6 +617,8 @@
 					# bind-parameter values to N bytes;
 					# -1 means print in full, 0 disables
 #log_statement = 'none'			# none, ddl, mod, all
+#max_log_size = 0 				# max size of logged statement_timeout (in bytes)
+				    # 0 disables the feature
 #log_replication_commands = off
 #log_temp_files = -1			# log temporary files equal or larger
 					# than the specified size in kilobytes;
diff --git a/src/bin/pg_ctl/t/004_logrotate.pl b/src/bin/pg_ctl/t/004_logrotate.pl
index eacca1a652..1c1f89cb0a 100644
--- a/src/bin/pg_ctl/t/004_logrotate.pl
+++ b/src/bin/pg_ctl/t/004_logrotate.pl
@@ -69,6 +69,7 @@ log_destination = 'stderr, csvlog, jsonlog'
 # these ensure stability of test results:
 log_rotation_age = 0
 lc_messages = 'C'
+max_log_size = 32
 ));
 
 $node->start();
@@ -135,6 +136,20 @@ check_log_pattern('stderr', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('csvlog', $new_current_logfiles, 'syntax error', $node);
 check_log_pattern('jsonlog', $new_current_logfiles, 'syntax error', $node);
 
+$node->psql('postgres', 'INSERT INTO SOME_NON_EXISTANT_TABLE VALUES (TEST)');
+for (my $attempts = 0; $attempts < $max_attempts; $attempts++)
+{
+	eval {
+		$current_logfiles = slurp_file($node->data_dir . '/current_logfiles');
+	};
+	last unless $@;
+	usleep(100_000);
+}
+die $@ if $@;
+check_log_pattern('stderr',  $current_logfiles, 'INSERT INTO SOME_NON_EXISTANT_TA(?!(BLE VALUES \(TEST\)))', $node);
+check_log_pattern('csvlog',  $current_logfiles, 'INSERT INTO SOME_NON_EXISTANT_TA(?!(BLE VALUES \(TEST\)))', $node);
+check_log_pattern('jsonlog', $current_logfiles, 'INSERT INTO SOME_NON_EXISTANT_TA(?!(BLE VALUES \(TEST\)))', $node);
+
 $node->stop();
 
 done_testing();
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index e54eca5b48..f6689796a5 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -502,6 +502,7 @@ extern PGDLLIMPORT int Log_destination;
 extern PGDLLIMPORT char *Log_destination_string;
 extern PGDLLIMPORT bool syslog_sequence_numbers;
 extern PGDLLIMPORT bool syslog_split_messages;
+extern PGDLLIMPORT int max_log_size;
 
 /* Log destination bitmap */
 #define LOG_DESTINATION_STDERR	 1
@@ -516,6 +517,7 @@ extern void log_status_format(StringInfo buf, const char *format,
 extern void DebugFileOpen(void);
 extern char *unpack_sql_state(int sql_state);
 extern bool in_error_recursion_trouble(void);
+extern char* build_query_log(const char* query, bool *copied);
 
 /* Common functions shared across destinations */
 extern void reset_formatted_start_time(void);
-- 
2.39.2 (Apple Git-143)