Overview

The logical datacenter diagram communicates important information to developers about the target environment into which their application systems will be deployed.  The Logical datacenter Designer is used to create the logical representation of the logical datacenters.  Logical Datacenter designer does not give any information about the physical machines or even machine types in a datacenter.  It is, however, used to define or document the configurations of application server software such as IIS, SQL Server or BizTalk server and to show how these configured logical servers are interconnected.

Using logical datacenter designer, we can define zones and logical servers.  The zone represents the communication or the other datacenter boundaries.  A single machine in the physical environment can be represented by combining multiple logical server diagrams.  A physical server with Windows Server 2003, Internet Information Services (IIS) 6.0, and SQL Server would be represented by three separate logical servers.  After defining the servers, we can include the communication pathways between the servers.  Using the settings and constraints editor we can define the types of applications the server can host, the allowed settings for the hosted applications and configure the settings for the server.  We can also create reusable custom prototypes.

Logical datacenter Designer is fully integrated in Visual Studio 2005.  Architects and developers can use these diagrams in their deployment designer.  They can validate the deployment of the applications against the constraints defined in the datacenter diagrams.

Creating logical datacenters

We will see in action how to create a logical datacenter.  The datacenter contains two IIS web servers and one database server.  The first IIS web server hosts the application of presentation tier.  The second IIS web server hosts the web services consumed by the presentation tier application.  The database server will host the database used by the application.  We will create one single logical diagram to represent these servers.  The logical diagram is not directly mapped to the physical machines or servers.  Multiple logical servers may be used to represent a single physical machine or a single logical server may be used to represent multiple physical machines.  Let us create the logical datacenter diagram using visual studio 2005.

In Visual Studio 2005 select the option File | New | Project | Distributed System Solutions | Logical Datacenter.  Name the new project as "LogicalDatacenterDemo."  Now the solution gets created with one file in the items list as "LogicalDatacenterDemo.ldd."

Figure 1

The logical datacenter designer comes with the following five default elements in the Toolbox. 

·              IISWebServer – A server that hosts ASP.Net Applications.

·              DatabaseServer - A server that host the database.

·              Generic Server - Represents a custom server type.

·              WindowsClient – Represents a client.user machine.

·              Zone – A logical boundary such as a firewall.

The Toolbox of the logical datacenter also contains the following six different endpoints with three endpoints for the client side and three endpoints for the server side.

·              WebsiteEndpoint - Server side of HTTP connection

·              HTTPClientEndpoint - Client side of an HTTP connection

·              DatabaseClientEndpoint - Consumer of a database connection   

·              GenericServerEndpoint - Server side of a custom created server connection

·              GenericClientEndpoint – Client side of a non specific connection

·              ZoneEndpoint – Communication endpoint on the zone

Using the Toolbox, drag and drop two IISWebServer and one Database Servers on the logical designer surface.  These elements have default endpoints that represent the connection points for communication paths within a datacenter.  Communication can occur only through the connected endpoints.  By default the elements can have zero, one or multiple endpoints.  You can see the IISWebServer as having two endpoints by default and the Database Server as having only one endpoint by default.  The IISWebServer element exposes a WebSiteEndpoint that defines the incoming server side calls and an HTTPClientEndpoint that represents outgoing connections from the webserver.  To define the communication path between the endpoints, hold the ALT key while dragging one endpoint to a compatible endpoint.  This can also be done using the “Connect…” option from the context menu of the server.  Using the “Create Connection” dialog you can choose the target logical server or zone and the corresponding endpoint to create the connection.

Figure 2

The connection paths must be made between the compatible endpoints.  For example, if you try to connect the service tier web server with the Database server endpoint, you will see no drop mouse cursor and you will not be able to connect the two.  You must choose the compatible endpoints from the Toolbox for the servers.

Constraints and Settings for the logical servers

The Constraints and Settings editor is used to set the policies required for the model.  Using this editor we can configure settings on applications, endpoints, logical servers and zones.  We can also import existing settings from the IIS web server and we can also have our own custom settings.  To get the Constraints and Setting editor, right click on the server, which opens the context menu, and choose the option "Settings and Constraints."

Figure 3

 

The editor displays the different types of settings and constraints in a tree form with two top level nodes as “Application Constraints” and “Logical Server Settings.”  These are the options for the “IISWebServer.”  The settings and constraints will differ with the type of the logical server.  The “Application Constraints” node displays the pre-defined and user defined constraints.  On selecting a pre-defined constraint, the settings or options are displayed for the selected constraints.  Initially the settings for the selected constraints are disabled.  These options get enabled upon choosing the particular constraint checkbox.  For example, on choosing the “ASP.Net Security” constraint checkbox the settings like “Allowed security modes” will get enabled.  Upon choosing the forms security mode, the “Forms authentication” options is enabled so that you can choose the appropriate options for your application.

Figure 4

On choosing the ASP.NET Session State, you can see different options for maintaining the session state, Http cookie modes and the settings for SQL Server and State Server, which depends on the selected session mode.

Using the Logical Server Settings node you can define the settings required for the server to host the application.

You can also import the exiting IIS Server settings using the “Import IIS settings wizard.”  To get this Wizard, right click on the Settings and choose the option “Import Settings…” from the context menu.

Figure 5

 

Figure 6

 

 

 

Zones & Adding Zones to the Logical Datacenter Designer

Zones represent the communication boundaries in the datacenter.  It can represent a physical boundary or a logical boundary.  The physical boundary can be a machine in another network or in a different place.  The logical boundary could be a firewall.  You can add logical servers and zones to the zones.  Follow these steps to add zones to the logical datacenter diagram.

·         Drag and drop the required number of zone elements to design surface.

·         Select the logical server IISWebServer1.  Drag and drop the server into the zone element.  Now you can see that the connection between the IISWebServer1 and IISWebServer2 is broken.  In this same way add the second IISWebServer2 into the second zone.

·         You can see two different endpoints on the Zone elements.  One represents the inbound communication to the zone and the other denotes the outbound communication from the zone.  Now connect the outbound communication endpoint of the first zone to the inbound communication endpoint of the second zone.  You can add zone endpoints from the toolbox if it is required.  There is a third type of endpoint which is a bidirectional endpoint. This represents the communication flow between the two zones in both ways.

·         Now connect the HTTPClientEndpoint of the IISWebServer1 to the outbound endpoint of the zone in which the IISWebServer1 resides.  In the same way connect the inbound endpoint of the second zone to the WebSiteEndpoint of the IISWebServer2.  Now you can see that both zones are connected and both web servers are connected.  You can place the DatabaseServer element into the second zone or create a new zone and place the database server as per the requirement.

Figure 7

You can configure the zones using the Settings and Constraints Editor.  You can configure the type of logical servers that the zone can contain and the communication protocols that can pass into or out of the zone.  You can also add custom settings to the zones.  The configured zone can be made as a reusable prototype and added to the Toolbox.

Summary

In this article you have learned how to work with the Logical Datacenter Designer using Visual Studio 2005.