Created initial Readme.md

README.md

@@ -1,2 +1,68 @@
-# event-registry
-SImple registry that uses Zookeeper to keep track of event types, topics etc.
+# The event-registry
+Simple registry that uses Zookeeper to keep track of event types, topics etc. It is implemented as a simple wrapper around the apache curator zookeeper library that adds a simple model and zookeeper manipulation operations.
+
+Each update to the registry can generate events that different listeners can receive. So, for exmaple, when a new EventType is registered a router component could receive this update and create any necessary topics. Likewise when a component expresses an interest in a type of event (via an ```@Consumes``` annotation, connections to the correct topic can be made.
+
+
+# Connecting to the Registry
+
+To use the registry, make a connection to a running zookeeper server and start the connection:
+
+```
+RegistryConnetion connection = new RegistryConnection("localhost:2181");
+connection.setBaseKey("/streamzi")
+connection.connect();
+```
+
+The connection is created with a base key argument which attaches to the specified point in the Zookeeper data. All operations are then relative to that base key.
+
+# Updating the Registry
+
+When a registry connection has been made, updates are made via ```RegistryOperations```. These can either run asynchronously or synchronously. For example, to register a new EventType synchronously:
+
+```
+connection.executeSync(new CreateEventType(new EventType("MeterReading"));
+
+```
+or
+
+```
+connection.execute(new CreateEventType(new EventType("MeterReading")).thenRun(
+	new Runnable(){
+		public void run(){
+			System.out.println("Event type added");
+		}
+	}
+
+);
+```
+for an async operation.
+
+# Listening to changes
+
+Registry listeners can be created to listen for changes to specific object types. For example to listen for changes to EventTypes:
+
+```
+	RegistryKeyListener<EventType> listner = connection.addKeyListener(new RegistryKeyListener<>(){
+		@Override
+		public void objectAdded(EventType value){
+		}
+		
+		@Override
+		public void objectRemoved(EventType value){
+		}
+	
+		@Override
+		public void objectChanged(EventType value({
+		}
+	
+	});
+
+```
+
+Listeners are attached to a specific ```key``` in the Zookeeper tree and listen for child events on that key. They also keep a cache of the current state, so can be iterrogated directly:
+
+```
+	List<EventType> eventTypes = listener.getValues();
+```
+will return the locally cached list of event types.