fix: fixed Replication lags evaluation

Author: cuprumtan

mamonsu/plugins/pgsql/driver/pool.py

@@ -65,7 +65,7 @@ class Pool(object):
             """
             SELECT application_name,
                    {0}
-                   (pg_{1}_{2}_diff(pg_current_{1}_{2}(), replay_lsn))::int AS total_lag
+                   coalesce((pg_{1}_{2}_diff(pg_current_{1}_{2}(), replay_lsn))::int, 0) AS total_lag
             FROM pg_stat_replication;
             """,
             """

mamonsu/plugins/pgsql/replication.py

@@ -51,11 +51,11 @@ def run(self, zbx):
             Pooler.run_sql_type("replication_lag_master_query")
             if Pooler.server_version_greater("10.0") and (Pooler.is_superuser() or Pooler.is_bootstraped()):
                 result_lags = Pooler.run_sql_type("wal_lag_lsn",
-                                                  args=[" (pg_wal_lsn_diff(pg_current_wal_lsn(), sent_lsn))::int AS send_lag, "
-                                                        "(pg_wal_lsn_diff(sent_lsn, flush_lsn))::int AS receive_lag, "
-                                                        "(pg_wal_lsn_diff(sent_lsn, write_lsn))::int AS write_lag, "
-                                                        "(pg_wal_lsn_diff(write_lsn, flush_lsn))::int AS flush_lag, "
-                                                        "(pg_wal_lsn_diff(flush_lsn, replay_lsn))::int AS replay_lag, " if not Pooler.is_bootstraped() else
+                                                  args=[" coalesce((pg_wal_lsn_diff(pg_current_wal_lsn(), sent_lsn))::int, 0) AS send_lag, "
+                                                        "coalesce((pg_wal_lsn_diff(sent_lsn, flush_lsn))::int, 0) AS receive_lag, "
+                                                        "coalesce((pg_wal_lsn_diff(sent_lsn, write_lsn))::int, 0) AS write_lag, "
+                                                        "coalesce((pg_wal_lsn_diff(write_lsn, flush_lsn))::int, 0) AS flush_lag, "
+                                                        "coalesce((pg_wal_lsn_diff(flush_lsn, replay_lsn))::int, 0) AS replay_lag, " if not Pooler.is_bootstraped() else
                                                         " send_lag, receive_lag, write_lag, flush_lag, replay_lag, ",
                                                         "wal", "lsn"])
                 if result_lags:

mamonsu/tools/bootstrap/sql.py

@@ -185,7 +185,7 @@
 RETURNS TABLE(application_name TEXT, {8} total_lag INTEGER) AS $$
 SELECT application_name,
        {6} 
-       (pg_{7}_diff(pg_current_{7}(), replay_{9}))::int AS total_lag
+       coalesce((pg_{7}_diff(pg_current_{7}(), replay_{9}))::int, 0) AS total_lag
 FROM pg_stat_replication
 $$ LANGUAGE SQL SECURITY DEFINER;
 """

mamonsu/tools/bootstrap/start.py

@@ -166,11 +166,11 @@ def fill_query_params(queries):
             'wal_lsn' if Pooler.server_version_greater('10.0') else 'xlog_location',
             'waiting' if Pooler.server_version_less('9.6.0') else 'case when wait_event_type is null then false '
                                                                   ' else true end  as waiting',
-            '(pg_wal_lsn_diff(pg_current_wal_lsn(), sent_lsn))::int AS send_lag, '
-            '(pg_wal_lsn_diff(sent_lsn, flush_lsn))::int AS receive_lag, '
-            '(pg_wal_lsn_diff(sent_lsn, write_lsn))::int AS write_lag, '
-            '(pg_wal_lsn_diff(write_lsn, flush_lsn))::int AS flush_lag, '
-            '(pg_wal_lsn_diff(flush_lsn, replay_lsn))::int AS replay_lag,' if Pooler.server_version_greater('10.0') else '',
+            'coalesce((pg_wal_lsn_diff(pg_current_wal_lsn(), sent_lsn))::int, 0) AS send_lag, '
+            'coalesce((pg_wal_lsn_diff(sent_lsn, flush_lsn))::int, 0) AS receive_lag, '
+            'coalesce((pg_wal_lsn_diff(sent_lsn, write_lsn))::int, 0) AS write_lag, '
+            'coalesce((pg_wal_lsn_diff(write_lsn, flush_lsn))::int, 0) AS flush_lag, '
+            'coalesce((pg_wal_lsn_diff(flush_lsn, replay_lsn))::int, 0) AS replay_lag,' if Pooler.server_version_greater('10.0') else '',
             'wal_lsn' if Pooler.server_version_greater('10.0') else 'xlog_location',
             'send_lag INTEGER, receive_lag INTEGER, write_lag INTEGER, flush_lag INTEGER, replay_lag INTEGER,' if Pooler.server_version_greater('10.0')
             else '',