[Node] add ErrorHandler

scheme/link.py

@@ -61,8 +61,8 @@ class Link(object):
     _JSON_SINK_NODE_ID = 'sink_node_id'
     _JSON_LINK_ID = 'link_id'
 
-    def __init__(self, source_node, sink_node, source_channel, sink_channel,
-                 id=None):
+    def __init__(self, source_node, sink_node, source_channel='default',
+                 sink_channel='default', id=None):
         self.id = get_next_link_free_id() if id is None else id
         if isinstance(source_node, int):
             self.source_node_id = source_node

scheme/node.py

@@ -86,6 +86,7 @@ class Node(object):
     _JSON_PROCESS_PT = 'process_pt'
     _JSON_ID = 'id'
     _JSON_PROPERTIES = 'properties'
+    _JSON_ERROR_HANDLER = 'error_handler'
 
     def __init__(self, processing_pt, id=None, properties=None,
                  error_handler=None):
@@ -209,11 +210,19 @@ class Node(object):
         :return: json description of the node
         :rtype: dict
         """
-        return {
+        res = {
             self._JSON_PROCESS_PT: self.process_pt,
             self._JSON_ID: self.id,
             self._JSON_PROPERTIES: self.properties,
         }
+        res.update(self._get_error_handler_json())
+        return res
+
+    def _get_error_handler_json(self):
+        error_handler_json = self._error_handler.to_json() if self._error_handler else {}
+        return {
+            self._JSON_ERROR_HANDLER: error_handler_json,
+        }
 
     @staticmethod
     def from_json(json_data):
@@ -264,3 +273,16 @@ class WorkflowException(Exception):
         self.errorMessage = msg
         self.data = data
         self.traceBack = traceBack
+
+
+class ErrorHandler(Node):
+    '''
+    TODO
+    '''
+    def __init__(self, processing_pt, id=None, properties=None):
+        super(ErrorHandler, self).__init__(processing_pt=processing_pt, id=id,
+                                           properties=properties,
+                                           error_handler=None)
+
+    def _get_error_handler_json(self):
+        return {}
\ No newline at end of file

scheme/scheme.py

@@ -123,7 +123,7 @@ class Scheme(object):
         :param output_file: name of the output file.
         :type: str
         """
-        if output_file.lower.endswith('.json'):
+        if output_file.lower().endswith('.json'):
             self.save_as_json(output_file)
         else:
             self.save_as_xml(output_file)