--read-only option to add mcs node add

Author: mariadb-AlexanderPresniakov

cmapi/cmapi_server/handlers/cluster.py

@@ -196,7 +196,8 @@ def process_shutdown():
     @staticmethod
     def add_node(
         node: str, config: str = DEFAULT_MCS_CONF_PATH,
-        logger: logging.Logger = logging.getLogger('cmapi_server')
+        logger: logging.Logger = logging.getLogger('cmapi_server'),
+        read_only: bool = False,
     ) -> dict:
         """Method to add node to MCS CLuster.
 
@@ -207,6 +208,8 @@ def add_node(
         :type config: str, optional
         :param logger: logger, defaults to logging.getLogger('cmapi_server')
         :type logger: logging.Logger, optional
+        :param read_only: add node in read-only mode, defaults to False
+        :type read_only: bool, optional
         :raises CMAPIBasicError: on exception while starting transaction
         :raises CMAPIBasicError: if transaction start isn't successful
         :raises CMAPIBasicError: on exception while adding node
@@ -238,13 +241,18 @@ def add_node(
         try:
             add_node(
                 node, input_config_filename=config,
-                output_config_filename=config
+                output_config_filename=config,
+                read_only=read_only,
             )
             if not get_dbroots(node, config):
-                add_dbroot(
-                    host=node, input_config_filename=config,
-                    output_config_filename=config
-                )
+                if not read_only:  # Read-only nodes don't own dbroots
+                    add_dbroot(
+                        host=node, input_config_filename=config,
+                        output_config_filename=config
+                    )
+                else:
+                    logger.debug("Node %s is read-only, skipping dbroot addition", node)
+
         except Exception as err:
             rollback_transaction(transaction_id, cs_config_filename=config)
             raise CMAPIBasicError('Error while adding node.') from err

cmapi/cmapi_server/node_manipulation.py

@@ -55,13 +55,14 @@ def switch_node_maintenance(
         maintenance_element = etree.SubElement(config_root, 'Maintenance')
     maintenance_element.text = str(maintenance_state).lower()
     node_config.write_config(config_root, filename=output_config_filename)
-    # TODO: probably move publishing to cherrypy.emgine failover channel here?
+    # TODO: probably move publishing to cherrypy.engine failover channel here?
 
 
 def add_node(
     node: str, input_config_filename: str = DEFAULT_MCS_CONF_PATH,
     output_config_filename: Optional[str] = None,
-    rebalance_dbroots: bool = True
+    rebalance_dbroots: bool = True,
+    read_only: bool = False,
 ):
     """Add node to a cluster.
 
@@ -96,14 +97,16 @@ def add_node(
         if not _replace_localhost(c_root, node):
             pm_num = _add_node_to_PMS(c_root, node)
 
-            if not node_config.is_read_only():
+            if not read_only:
                 _add_WES(c_root, pm_num, node)
+            else:
+                _add_read_only_node(c_root, node)
 
             _add_DBRM_Worker(c_root, node)
             _add_Module_entries(c_root, node)
             _add_active_node(c_root, node)
             _add_node_to_ExeMgrs(c_root, node)
-            if rebalance_dbroots:
+            if rebalance_dbroots and not read_only:
                 _rebalance_dbroots(c_root)
                 _move_primary_node(c_root)
     except Exception:
@@ -368,7 +371,7 @@ def _remove_node(root, node):
     remove node from DesiredNodes, InactiveNodes, and ActiveNodes
     '''
 
-    for n in (root.find("./DesiredNodes"), root.find("./InactiveNodes"), root.find("./ActiveNodes")):
+    for n in (root.find("./DesiredNodes"), root.find("./InactiveNodes"), root.find("./ActiveNodes"), root.find("./ReadOnlyNodes")):
         __remove_helper(n, node)
 
 
@@ -978,6 +981,15 @@ def _add_WES(root, pm_num, node):
     etree.SubElement(wes_node, "Port").text = "8630"
 
 
+def _add_read_only_node(root, node) -> None:
+    """Add node name to ReadOnlyNodes if it's not already there"""
+    read_only_nodes = root.find("./ReadOnlyNodes")
+    for n in read_only_nodes.findall("./Node"):
+        if n.text == node:
+            return
+    etree.SubElement(read_only_nodes, "Node").text = node
+
+
 def _add_DBRM_Worker(root, node):
     '''
     find the highest numbered DBRM_Worker entry, or one that isn't used atm

cmapi/mcs_cluster_tool/cluster_app.py

@@ -190,12 +190,17 @@ def add(
             'node IP, name or FQDN. '
             'Can be used multiple times to add several nodes at a time.'
         )
+    ),
+    read_only: bool = typer.Option(
+        False,
+        '--read-only',
+        help='Add node (or nodes, if more than one is passed) in read-only mode.'
     )
 ):
     """Add nodes to the Columnstore cluster."""
     result = []
     for node in nodes:
-        result.append(ClusterHandler.add_node(node, logger=logger))
+        result.append(ClusterHandler.add_node(node, logger=logger, read_only=read_only))
     return result