Update history examples

Cleanup examples and add an example for historizing a data value

examples/server-datavalue-history.py

+import sys
+sys.path.insert(0, "..")
+import time
+import math
+
+
+from opcua import ua, Server
+from opcua.server.history_sql import HistorySQLite
+
+
+if __name__ == "__main__":
+
+    # setup our server
+    server = Server()
+    server.set_endpoint("opc.tcp://0.0.0.0:4840/freeopcua/server/")
+
+    # setup our own namespace, not really necessary but should as spec
+    uri = "http://examples.freeopcua.github.io"
+    idx = server.register_namespace(uri)
+
+    # get Objects node, this is where we should put our custom stuff
+    objects = server.get_objects_node()
+
+    # populating our address space
+    myobj = objects.add_object(idx, "MyObject")
+    myvar = myobj.add_variable(idx, "MyVariable", ua.Variant(0, ua.VariantType.Double))
+    myvar.set_writable()  # Set MyVariable to be writable by clients
+
+    # Configure server to use sqlite as history database (default is a simple in memory dict)
+    server.iserver.history_manager.set_storage(HistorySQLite("my_datavalue_history.sql"))
+
+    # starting!
+    server.start()
+
+    # enable data change history for this particular node, must be called after start since it uses subscription
+    server.iserver.enable_history_data_change(myvar, period=None, count=100)
+
+    try:
+        count = 0
+        while True:
+            time.sleep(1)
+            count += 0.1
+            myvar.set_value(math.sin(count))
+
+    finally:
+        # close connection, remove subscriptions, etc
+        server.stop()

examples/server-events-history.py

 import sys
 sys.path.insert(0, "..")
 import time
-import logging
-
+from datetime import datetime
 
 from opcua import ua, Server
 from opcua.server.history_sql import HistorySQLite
@@ -23,8 +22,6 @@ if __name__ == "__main__":
 
     # populating our address space
     myobj = objects.add_object(idx, "MyObject")
-    myvar = myobj.add_variable(idx, "MyVariable", ua.Variant(0, ua.VariantType.Double))
-    myvar.set_writable()  # Set MyVariable to be writable by clients
 
     # Creating a custom event: Approach 1
     # The custom event object automatically will have members from its parent (BaseEventType)
@@ -35,15 +32,18 @@ if __name__ == "__main__":
     etype2 = server.create_custom_event_type(2, 'MySecondEvent', ua.ObjectIds.BaseEventType,
                                              [('MyOtherProperty', ua.VariantType.Float)])
 
+    # get an event generator for the myobj node which generates custom events
     myevgen = server.get_event_generator(etype, myobj)
     myevgen.event.Severity = 500
     myevgen.event.MyStringProperty = ua.Variant("hello world")
     myevgen.event.MyNumericProperty = ua.Variant(-456)
 
+    # get another event generator for the myobj node which generates different custom events
     myevgen2 = server.get_event_generator(etype2, myobj)
     myevgen2.event.Severity = 123
     myevgen2.event.MyOtherProperty = ua.Variant(1.337)
 
+    # get an event generator for the server node which generates BaseEventType
     serverevgen = server.get_event_generator()
     serverevgen.event.Severity = 111
 
@@ -53,10 +53,10 @@ if __name__ == "__main__":
     # starting!
     server.start()
 
-    # enable history for myobj events
+    # enable history for myobj events; must be called after start since it uses subscription
     server.iserver.enable_history_event(myobj, period=None)
 
-    # enable history for server events
+    # enable history for server events; must be called after start since it uses subscription
     server_node = server.get_node(ua.ObjectIds.Server)
     server.iserver.enable_history_event(server_node, period=None)
 
@@ -65,11 +65,15 @@ if __name__ == "__main__":
         while True:
             time.sleep(1)
             count += 0.1
+
+            # generate events for subscribed clients and history
             myevgen.trigger(message="This is MyFirstEvent " + str(count))
             myevgen2.trigger(message="This is MySecondEvent " + str(count))
             serverevgen.trigger(message="Server Event Message")
 
-            res = server_node.read_event_history(None, None, 0)
+            # read event history from sql
+            end_time = datetime.utcnow()
+            server_event_history = server_node.read_event_history(None, end_time, 0)
 
     finally:
         # close connection, remove subscriptions, etc