Add batching functionality to delete_nodes

When `delete_nodes` is given a large amount of nodes, or is instructed
to recursively delete a big structure, the connection between client and
server can time out.

To remedy this, allow the user to supply a `batch` parameter, which
controls how many nodes are deleted in one request.

closes #1148

Author: Nebukadneza

opcua/client/client.py

@@ -586,8 +586,8 @@ def get_namespace_index(self, uri):
         uries = self.get_namespace_array()
         return uries.index(uri)
 
-    def delete_nodes(self, nodes, recursive=False):
-        return delete_nodes(self.uaclient, nodes, recursive)
+    def delete_nodes(self, nodes, recursive=False, batch=False):
+        return delete_nodes(self.uaclient, nodes, recursive, batch=batch)
 
     def import_xml(self, path=None, xmlstring=None):
         """

opcua/common/manage_nodes.py

@@ -372,10 +372,12 @@ def _guess_datatype(variant):
         return ua.NodeId(getattr(ua.ObjectIds, variant.VariantType.name))
 
 
-def delete_nodes(server, nodes, recursive=False, delete_target_references=True):
+def delete_nodes(server, nodes, recursive=False, delete_target_references=True, batch=False):
     """
-    Delete specified nodes. Optionally delete recursively all nodes with a
-    downward hierachic references to the node
+    Delete specified nodes. Optionally recursively delete all nodes with a
+    downward hierachic references to the node.
+    `batch` can be False or a integer. If a integer is given, batch the nodes
+    discovered into multiple DeleteNodesRequests.
     return the list of deleted node and the result
     """
     nodestodelete = []
@@ -386,9 +388,23 @@ def delete_nodes(server, nodes, recursive=False, delete_target_references=True):
         it.NodeId = mynode.nodeid
         it.DeleteTargetReferences = delete_target_references
         nodestodelete.append(it)
-    params = ua.DeleteNodesParameters()
-    params.NodesToDelete = nodestodelete
-    return nodes, server.delete_nodes(params)
+
+    if batch and isinstance(batch, int):
+        chunks = [
+            nodestodelete[i : i + batch]
+            for i in range(0, len(nodestodelete), batch)
+        ]
+
+        results = []
+        for chunk in chunks:
+            params = ua.DeleteNodesParameters()
+            params.NodesToDelete = chunk
+            results.extend(server.delete_nodes(params))
+        return nodes, results
+    else:
+        params = ua.DeleteNodesParameters()
+        params.NodesToDelete = nodestodelete
+        return nodes, server.delete_nodes(params)
 
 
 def _add_childs(nodes):

opcua/server/server.py

@@ -541,8 +541,8 @@ def export_xml_by_ns(self, path, namespaces=None):
         nodes = get_nodes_of_namespace(self, namespaces)
         self.export_xml(nodes, path)
 
-    def delete_nodes(self, nodes, recursive=False):
-        return delete_nodes(self.iserver.isession, nodes, recursive)
+    def delete_nodes(self, nodes, recursive=False, batch=False):
+        return delete_nodes(self.iserver.isession, nodes, recursive, batch=batch)
 
     def historize_node_data_change(self, node, period=timedelta(days=7), count=0):
         """

tests/tests_common.py

@@ -173,6 +173,30 @@ def test_delete_nodes_recursive2(self):
             with self.assertRaises(ua.UaStatusCodeError):
                 node.get_browse_name()
 
+    def test_delete_nodes_recursive_batching(self):
+        obj = self.opc.get_objects_node()
+        fold = obj.add_folder(2, "FolderToDeleteRoot")
+        nfold = fold
+        mynodes = []
+        for i in range(7):
+            nfold = fold.add_folder(2, "FolderToDeleteRoot")
+            var = fold.add_variable(2, "VarToDeleteR", 9.1)
+            var = fold.add_property(2, "ProToDeleteR", 9.1)
+            prop = fold.add_property(2, "ProToDeleteR", 9.1)
+            o = fold.add_object(3, "ObjToDeleteR")
+            o_var = o.add_variable(3, "VarToDeleteRR", 9.2)
+            o_prop = o.add_property(3, "PropToDeleteRR", 9.2)
+            mynodes.append(nfold)
+            mynodes.append(var)
+            mynodes.append(prop)
+            mynodes.append(o)
+            mynodes.append(o_var)
+            mynodes.append(o_prop)
+        self.opc.delete_nodes([fold], recursive=True, batch=2)
+        for node in mynodes:
+            with self.assertRaises(ua.UaStatusCodeError):
+                node.get_browse_name()
+
     def test_delete_references(self):
         newtype = self.opc.get_node(ua.ObjectIds.HierarchicalReferences).add_reference_type(0, "HasSuperSecretVariable")