Routing transactions in the presence of failing servers

摘要

Failures are detected in servers of a transaction processing system, and transactions are routed to less failure prone servers in the system. Servers in the transaction processing system which are faulty for some transaction classes but good for others are detected, and such servers are used in a judicious manner to maximize the throughput and minimize the response time of the system. Error prone servers are occasionally probed to determine if they have improved in terms of their error characteristics. The mechanism implemented consists of three elements. The first is the selection of a routing algorithm based on the state of the transaction processing system. Second, transactions are used to probe systems considered too faulty for use in order to determine if they have improved in terms of their failure characteristics. Finally, soft ABENDs are detected. The algorithm for transaction routing to detect and control the problem of failing servers in a transaction processing system consists of two parts: The first part routes transactions to servers based on the length of the server queues, the response time of the transactions (i.e., queuing delay plus processing delay), and the perceived failure rate. The second part of the algorithm ensures that error prone servers are not completely ignored. Occasional transactions are used to probe servers in order to determine if they have improved in terms of their error characteristics.