Error Injection Tool

Rajnesh Avtar

ABSTRACT

Handling error conditions and gracefully recovering from such situations is a critical area for any software product. It could involve handling of errors from attached hardware or any other software component. However, it is not always possible to re-create all error situations and test them. One of the mechanisms for testing the robustness of the code is to inject errors and ensure that the code paths are covered.

This project will provide an opportunity for students to develop a GUI interface to inject various errors in a client server environment. This will allow them to verify the error recovery code in the client and the handling of invalid commands in the server. It will also provide an opportunity for them to get an experience in inter process communications.

Background

In any computer system the Input Output system is an essential element. All I/Os have to be performed on attached devices. The IOPs written in the system have to handle various error conditions possibly returned by these devices. In the Tandem Non-Stop fault tolerant systems error recovery is one of the most critical areas of the code. We have to be able to tolerate any single point of failure without impacting the customer applications. Thus, it is essential for us to be able to test these various error situations.

One of the mechanisms to test these error conditions is to develop and use an error injector tool. This would provide the capability to inject any error from a normal device instead of trying to find devices that are broken and return various error conditions.

Proposal

To limit the scope of this project and to remove any dependence on a hardware component, it is being proposed that a client server environment be used. Here are the various components of the project:

1. A client that creates and sends messages for the server. (To simulate the operations performed by the IOPs it is suggested that the messages use the standard SCSI structures. This will also introduce the students to the SCSI terminology)
2. A server that processes the messages from the client and replies to these messages.
3. A GUI based error injection tool that injects errors specified by the user. It sends messages to the client to alter either the outgoing message to the server or incoming reply from the server.

• By altering the outgoing message to the server, a normal command is changed and made invalid without changing the client software. This will test the behavior of the server and ensure that it can handle invalid commands.

• By altering the incoming response from the server, a normal reply is changed without changing the server software. The client believes that the response from the server indicates an error condition. This will validate and verify the error recovery code in the client software.

ICS125 WQ00 Project Opportunities
ICS125 WQ00
David F. Redmiles ­ Home Page
Department of Information and Computer Science
University of California, Irvine CA 92717-3425