Fix timeline metric None value (patroni#3165)

Close patroni#3164

Author: UTXOnly

kubernetes/entrypoint.sh

@@ -15,6 +15,7 @@ bootstrap:
       pg_hba:
       - host all all 0.0.0.0/0 md5
       - host replication ${PATRONI_REPLICATION_USERNAME} ${PATRONI_KUBERNETES_POD_IP}/16 md5
+      - host replication ${PATRONI_REPLICATION_USERNAME} 127.0.0.1/32 md5
   initdb:
   - auth-host: md5
   - auth-local: trust

patroni/api.py

@@ -655,7 +655,7 @@ def do_GET_metrics(self) -> None:
 
         metrics.append("# HELP patroni_postgres_timeline Postgres timeline of this node (if running), 0 otherwise.")
         metrics.append("# TYPE patroni_postgres_timeline counter")
-        metrics.append("patroni_postgres_timeline{0} {1}".format(labels, postgres.get('timeline', 0)))
+        metrics.append("patroni_postgres_timeline{0} {1}".format(labels, postgres.get('timeline') or 0))
 
         metrics.append("# HELP patroni_dcs_last_seen Epoch timestamp when DCS was last contacted successfully"
                        " by Patroni.")