Add capability to specify restore command

docs/multisite.rst

@@ -134,6 +134,8 @@ Details of the configuration parameters
     Time to live of site leader lock. If the site is unable to elect a functioning leader within this timeout, a different site can take over the leader role.  Must be a few times longer than the usual ``ttl`` value in order to prevent unnecessary site failovers.
 ``retry_timeout``
     How long the global etcd cluster can be inaccessible before the cluster is demoted. Must be a few times longer than the usual ``retry_timeout`` value in order to prevent unnecessary site failovers.
+``restore_command``
+    PostgreSQL restore\_command to use to fetch WAL files from remote site.
 
 Passwords in the YAML configuration
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

patroni/multisite.py

@@ -184,6 +184,14 @@ def _replication_slot(self) -> Optional[str]:
         site_config = global_config.sites.get(self.name)
         return site_config and site_config.get('slot')
 
+    @property
+    def _restore_command(self) -> Optional[str]:
+        site_config = global_config.sites.get(self.name)
+        if site_config and 'restore_command' in site_config:
+            return site_config['restore_command']
+
+        return self.config.get('restore_command')
+
     def _disconnected_operation(self):
         self._standby_config = {'restore_command': 'false'}
 
@@ -207,6 +215,11 @@ def _set_standby_config(self, other: Member):
             slot = self._replication_slot
             if slot:
                 new_config['primary_slot_name'] = slot
+
+            restore_command = self._restore_command
+            if restore_command:
+                new_config['restore_command'] = restore_command
+
             old_conf, self._standby_config = self._standby_config, new_config
         except KeyError:
             old_conf = self._standby_config