Consistency maintaining replica in web services

This paper presents, an ISS (Intelligence Surrogate System) is used to manage the replication of the web services. The middleware uses the Time Stamp Based (TSR) protocol to handle the synchronization operations to ensure that the replicas’ states are consistent. A web service is replicated at several sites. Each replica consists of a proxy web service site (PWSS) and a web service site (WSS). The WSS is a conventional web service provider. It hosts the code and data that provide the functionality of the web services. The PWSS is residing between the clients and the WSS. It is responsible for ensuring the consistency of the replica. Clients interact with the PWSSs.

A client only needs to send its service request to one PWSS. The PWSSs are responsible for multicasting clients’ requests to other replicas and returning results to the clients. To maintain the consistency of the WSSs’ states, the PWSSs must ensure that all clients’ requests are executed on the WSSs in the same order. The replicas form a group, called service group. ATU (Auto Time Updater) is responsible to manage when none of response occurs.