use correct functions depending on psql major version

helpers/postgresql.py

@@ -12,6 +12,7 @@ def __init__(self, config):
         self.name = config["name"]
         self.host, self.port = config["listen"].split(":")
         self.data_dir = config["data_dir"]
+        self.version_file = os.path.join(self.data_dir, 'PG_VERSION')
         self.replication = config["replication"]
 
         self.config = config
@@ -65,6 +66,24 @@ def query(self, sql):
     def data_directory_empty(self):
         return not os.path.exists(self.data_dir) or os.listdir(self.data_dir) == []
 
+    def version_file_exists(self):
+        return not self.data_directory_empty() and os.path.isfile(self.version_file)
+
+    def postgres_version(self):
+        if self.version_file_exists():
+            try:
+                with open(self.version_file) as f:
+                    return f.read().strip()
+            except Exception:
+                logger.exception('Failed to read PG_VERSION from %s', self._data_dir)
+        return 0
+
+    def wal_name(self):
+        return 'wal' if self.postgres_version >= 10 else 'xlog'
+
+    def lsn_name(self):
+        return 'lsn' if self.postgres_version >= 10 else 'location'
+
     def initialize(self):
         if os.system("initdb %s" % self.initdb_options()) == 0:
             # start Postgres without options to setup replication user indepedent of other system settings
@@ -155,7 +174,7 @@ def is_healthiest_node(self, state_store):
                 member_conn = psycopg2.connect(member["address"])
                 member_conn.autocommit = True
                 member_cursor = member_conn.cursor()
-                member_cursor.execute("SELECT %s - (pg_last_xlog_replay_location() - '0/000000'::pg_lsn) AS bytes;" % self.xlog_position())
+                member_cursor.execute("SELECT %s - (pg_last_%s_replay_%s() - '0/000000'::pg_lsn) AS bytes;" % (self.xlog_position(), self.wal_name(), self.lsn_name()) )
                 xlog_diff = member_cursor.fetchone()[0]
                 logger.info([self.name, member["hostname"], xlog_diff])
                 if xlog_diff < 0:
@@ -219,10 +238,10 @@ def create_replication_user(self):
         self.query("CREATE USER \"%s\" WITH REPLICATION ENCRYPTED PASSWORD '%s';" % (self.replication["username"], self.replication["password"]))
 
     def xlog_position(self):
-        return self.query("SELECT pg_last_xlog_replay_location() - '0/0000000'::pg_lsn;").fetchone()[0]
+        return self.query("SELECT pg_last_%s_replay_%s() - '0/0000000'::pg_lsn;" % (self.wal_name(), self.lsn_name())).fetchone()[0]
 
     def last_operation(self):
         if self.is_leader():
-            return self.query("SELECT pg_current_xlog_location() - '0/00000'::pg_lsn;").fetchone()[0]
+            return self.query("SELECT pg_current_%s_%s() - '0/00000'::pg_lsn;" % (self.wal_name(), self.lsn_name())).fetchone()[0]
         else:
             return self.xlog_position()