Using CA Service Virtualization › CA Service Virtualization › High-level Virtualization Steps

High-level Virtualization Steps

The high-level steps in CA Service Virtualization are:

1. Take an image of the service behavior (service image); record transactions that the server handles.
2. Construct the virtual service from the behavior (virtual service model or VSM).
3. Deploy the VSM to the Virtual Service Environment (VSE). The VSM then looks at the captured service images to find the appropriate responses for requests coming in to the VSE.

The following graphics show that when recording the image, VSE acts as the pass through mechanism between the client and server. While VSE passes the requests and responses along, it records the transactions.

Normal Operation

Recording

At the time of virtualization, in the absence of the server, VSE responds to the client requests by consulting the recorded transactions.

Virtualization of Messaging Systems

Message-oriented middleware (MOM), or messaging systems, are services that provide a means to enable asynchronous communication between two or more software applications. This communication always happens in the form of messages. The messages are posted to message destinations configured in the MOM.

The types of message destinations are:

Queues

A publisher adds a message to the queue, and a subscriber pulls messages from the queue, in a "first in, first out" fashion.

Topics

A publisher publishes a message to a topic, and all subscribers that subscribe to the topic receive the message.

The following graphic shows a simple message-based service. In this scenario, the client adds messages to a queue (ORDERS.REQUEST), which the server picks up. The response from the server is in the form of messages added to another queue (ORDERS.RESPONSE). The client then picks them up.

Possible variations include:

• Using topics instead of queues
• Multiple responses to a single request, which can possibly target different destinations

CA Service Virtualization aims to virtualize the server. In the recording mode, VSE requires extra proxy destinations (requestProxy and responseProxy queues in the following graphic) that the client uses instead of their counterparts. The server still listens and posts to the real destinations. VSE acts as a pass through between these proxy and real destinations. VSE records the traffic to create the VSM and the service image that it needs for the virtualization.

Later, when VSE virtualizes the server, it works with the real destinations. VSE does not need the proxy destinations.