repmgrd: check binary and extension major versions match

repmgr requires that the same "major version" (e.g. 4.3) is present
on all nodes, otherwise - particularly in the case of repmgrd - it's
highly likely things won't work as expected.

Implements part of GitHub #515.

HISTORY

@@ -1,3 +1,6 @@
+4.3     2019-??
+        repmgrd: check binary and extension major versions match; GitHub #515 (Ian)
+
 4.2.1   2018-??-??
         repmgr: add sanity check for correct extension version (Ian)
         repmgr: ensure "witness register --dry-run" does not attempt to read node

dbutils.c

@@ -1904,9 +1904,9 @@ get_repmgr_extension_status(PGconn *conn, t_extension_versions *extversions)
 	appendPQExpBufferStr(&query,
 						 "	  SELECT ae.name, e.extname, "
 						 "           ae.default_version, "
-						 "           (ae.default_version::numeric * 10)::INT AS available, "
+						 "           (((ae.default_version::NUMERIC::INT) * 10000) + (ae.default_version::NUMERIC - ae.default_version::NUMERIC::INT) * 1000)::INT AS available, "
 						 "           ae.installed_version, "
-						 "           (ae.installed_version::numeric * 10)::INT AS installed "
+						 "           (((ae.installed_version::NUMERIC::INT) * 10000) + (ae.installed_version::NUMERIC - ae.installed_version::NUMERIC::INT) * 1000)::INT AS installed "
 						 "     FROM pg_catalog.pg_available_extensions ae "
 						 "LEFT JOIN pg_catalog.pg_extension e "
 						 "       ON e.extname=ae.name "
@@ -1936,7 +1936,9 @@ get_repmgr_extension_status(PGconn *conn, t_extension_versions *extversions)
 		if (extversions != NULL)
 		{
 			strncpy(extversions->default_version, PQgetvalue(res, 0, 2), 7);
+			extversions->default_version_num = available_version;
 			strncpy(extversions->installed_version, PQgetvalue(res, 0, 4), 7);
+			extversions->installed_version_num = installed_version;
 		}
 
 		if (available_version > installed_version)

dbutils.h

@@ -112,12 +112,16 @@ typedef enum
 
 typedef struct s_extension_versions {
 	char		default_version[8];
+	int			default_version_num;
 	char		installed_version[8];
+	int			installed_version_num;
 } t_extension_versions;
 
 #define T_EXTENSION_VERSIONS_INITIALIZER { \
 	"", \
+	UNKNOWN_SERVER_VERSION_NUM, \
 	"", \
+	UNKNOWN_SERVER_VERSION_NUM \
 }
 
 /*

repmgr_version.h.in

@@ -1,2 +1,3 @@
 #define REPMGR_VERSION_DATE ""
 #define REPMGR_VERSION "4.3dev"
+#define REPMGR_VERSION_NUM 40300

repmgrd.c

@@ -386,7 +386,39 @@ main(int argc, char **argv)
 	/* Check "repmgr" the extension is installed */
 	extension_status = get_repmgr_extension_status(local_conn, &extversions);
 
-	if (extension_status != REPMGR_INSTALLED)
+	if (extension_status == REPMGR_INSTALLED)
+	{
+		/*
+		 * extension is the latest available according to "pg_available_extensions" -
+		 * - does our (major) version match that?
+		 */
+		log_verbose(LOG_DEBUG, "binary version: %i; extension version: %i",
+					REPMGR_VERSION_NUM, extversions.installed_version_num);
+		if ((REPMGR_VERSION_NUM/100) < (extversions.installed_version_num / 100))
+		{
+			log_error(_("this \"repmgr\" version is older than the installed \"repmgr\" extension version"));
+			log_detail(_("\"repmgr\" version %s is installed but extension is version %s"),
+					   REPMGR_VERSION,
+					   extversions.installed_version);
+
+			log_hint(_("verify the repmgr installation on this server is updated properly before continuing"));
+			close_connection(&local_conn);
+			exit(ERR_BAD_CONFIG);
+		}
+
+		if ((REPMGR_VERSION_NUM/100) > (extversions.installed_version_num / 100))
+		{
+			log_error(_("this \"repmgr\" version is newer than the installed \"repmgr\" extension version"));
+			log_detail(_("\"repmgr\" version %s is installed but extension is version %s"),
+					   REPMGR_VERSION,
+					   extversions.installed_version);
+
+			log_hint(_("verify the repmgr extension is updated properly before continuing"));
+			close_connection(&local_conn);
+			exit(ERR_BAD_CONFIG);
+		}
+	}
+	else
 	{
 		/* this is unlikely to happen */
 		if (extension_status == REPMGR_UNKNOWN)
@@ -400,11 +432,10 @@ main(int argc, char **argv)
 		if (extension_status == REPMGR_OLD_VERSION_INSTALLED)
 		{
 			log_error(_("an older version of the \"repmgr\" extension is installed"));
-			log_detail(_("version %s is installed but newer version %s is available"),
+			log_detail(_("extension version %s is installed but newer version %s is available"),
 					   extversions.installed_version,
 					   extversions.default_version);
 			log_hint(_("verify the repmgr installation is updated properly before continuing"));
-
 		}
 		else
 		{