v24-0003-Add-version-check-for-standby-server.patch

From d91ff97100ae31e01dccdc4fe7497abd3fe39cd8 Mon Sep 17 00:00:00 2001
From: Shlok Kyal <shlok.kyal.oss@gmail.com>
Date: Wed, 14 Feb 2024 16:27:15 +0530
Subject: [PATCH v24 03/18] Add version check for standby server

Add version check for standby server
---
 doc/src/sgml/ref/pg_createsubscriber.sgml   |  6 +++++
 src/bin/pg_basebackup/pg_createsubscriber.c | 28 +++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/doc/src/sgml/ref/pg_createsubscriber.sgml b/doc/src/sgml/ref/pg_createsubscriber.sgml
index 7cdd047d67..9d0c6c764c 100644
--- a/doc/src/sgml/ref/pg_createsubscriber.sgml
+++ b/doc/src/sgml/ref/pg_createsubscriber.sgml
@@ -125,6 +125,12 @@ PostgreSQL documentation
      databases and walsenders.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     Both the target and source instances must have same major versions with
+     <application>pg_createsubscriber</application>.
+    </para>
+   </listitem>
   </itemizedlist>
 
   <note>
diff --git a/src/bin/pg_basebackup/pg_createsubscriber.c b/src/bin/pg_basebackup/pg_createsubscriber.c
index 205a835d36..b15769c75b 100644
--- a/src/bin/pg_basebackup/pg_createsubscriber.c
+++ b/src/bin/pg_basebackup/pg_createsubscriber.c
@@ -23,6 +23,7 @@
 #include "common/file_perm.h"
 #include "common/logging.h"
 #include "common/restricted_token.h"
+#include "common/string.h"
 #include "fe_utils/recovery_gen.h"
 #include "fe_utils/simple_list.h"
 #include "getopt_long.h"
@@ -294,6 +295,8 @@ check_data_directory(const char *datadir)
 {
 	struct stat statbuf;
 	char		versionfile[MAXPGPATH];
+	FILE	   *ver_fd;
+	char		rawline[64];
 
 	pg_log_info("checking if directory \"%s\" is a cluster data directory",
 				datadir);
@@ -317,6 +320,31 @@ check_data_directory(const char *datadir)
 		return false;
 	}
 
+	/* Check standby server version */
+	if ((ver_fd = fopen(versionfile, "r")) == NULL)
+		pg_fatal("could not open file \"%s\" for reading: %m", versionfile);
+
+	/* Version number has to be the first line read */
+	if (!fgets(rawline, sizeof(rawline), ver_fd))
+	{
+		if (!ferror(ver_fd))
+			pg_fatal("unexpected empty file \"%s\"", versionfile);
+		else
+			pg_fatal("could not read file \"%s\": %m", versionfile);
+	}
+
+	/* Strip trailing newline and carriage return */
+	(void) pg_strip_crlf(rawline);
+
+	if (strcmp(rawline, PG_MAJORVERSION) != 0)
+	{
+		pg_log_error("standby server is of wrong version");
+		pg_log_error_detail("File \"%s\" contains \"%s\", which is not compatible with this program's version \"%s\".",
+							versionfile, rawline, PG_MAJORVERSION);
+		exit(1);
+	}
+
+	fclose(ver_fd);
 	return true;
 }
 
-- 
2.43.0