Failure-monitoring program and load-balancing device

A failure-monitoring method for monitoring destination servers for failure in order to deliver request packets from clients to the destination servers and balance loads imposed on the destination servers, comprising the steps of:

• (a) generating and storing for each of said destination servers definition-for-monitoring information in which one or more servers to be monitored, a monitoring procedure including a definition of a monitoring packet used in diagnosis of the one or more servers to be monitored, and, when necessary, a criterion for determining normality of the one or more servers to be monitored are defined;
• (b) transmitting said monitoring packet defined in said monitoring procedure to each of said one or more servers to be monitored, in accordance with said definition-for-monitoring information;
• and
• (c) determining that said each of the one or more servers to be monitored is faulty and delivery of one or more request packets to one of the destination servers corresponding to said each of the one or more servers to be monitored is not allowed, when no response is returned from said each of said one or more servers to be monitored, or when a response packet received from said each of the one or more servers to be monitored does not satisfy said criterion.

A load-balancing device for delivering request packets from clients to destination servers so as to balance loads imposed on the destination servers, and monitoring the destination servers for failure, comprising:

• a definition-management unit which generates destination information in which said destination servers are defined as servers to which said request packets from said clients are to be delivered, generates definition-for-monitoring information for each of said destination servers, and manages the destination information and the definition-for-monitoring information, where one or more servers to be monitored, a monitoring procedure including a definition of a monitoring packet used in diagnosis of the one or more servers to be monitored, and, when necessary, a criterion for determining normality of the one or more servers to be monitored are defined in said definition-for-monitoring information;
• a failure-monitoring unit which transmits said monitoring packet defined in said monitoring procedure to each of said one or more servers to be monitored, in accordance with said definition-for-monitoring information, determines that said each of the one or more servers to be monitored is faulty and delivery of one or more request packets to one of the destination servers corresponding to said each of the one or more servers to be monitored is not allowed, when no response is returned from said each of said one or more servers to be monitored, or when a response packet received from said each of the one or more servers to be monitored does not satisfy said criterion, and determines that delivery of one or more request packets to one of the destination servers corresponding to said each of the one or more servers to be monitored is allowed when the response packet received from said each of the one or more servers to be monitored satisfies said criterion;
• and
• a delivery unit which delivers a request packet from a client to one of said destination servers to which delivery of one or more request packets is determined to be allowed, when the request packet is received from the client.