FACETA*: Checkpointing for Transactional Composite Web Service Execution based on Petri-Nets

Abstract

International audienceFailures during the execution of Transactional Composite Web Services (TCWSs) can be repaired by forward or back–ward recovery processes, according to the component WSs transactional properties. In previous works, we presented TCWS fault tolerant execution approaches relying on WSs replacement, on a compensation protocol, and on unrolling processes of Colored Petri-Nets (CPNs) to support forward and backward recovery. We represent a TCWS and its corresponding backward recovery process by CPNs. Even though these recovery processes ensure system consistency, backward recovery means that users do not get the desired answer to their queries and forward recovery could imply long waiting time for users to finally get the desired response. In this paper, we present an alternative fault tolerant approach in which, in case of failures, the unrolling process of the CPN controlling the execution of a TCWS is check–pointed and the execution flow goes on as much as it is possible. In this way, users can have partial responses as soon as they are received and can re-submit the checkpointed CPN to re-start its execution from an advanced point of execution (checkpoint). We present the checkpointing algorithm integrated to our previous work

Overview on Fault Tolerance Strategies of Composite Service in Service Computing

“…If the effects produced by the faulty component service need to be compensated [27], backward recovery is allowed [28]. However, users need to wait a long time to get the desired response when forward recovery is adopted, and users are unable to get the desired answer to their queries when backward recovery is adopted [29]. Taking checkpoint is another dynamic fault tolerance strategy.…”

“…In [29], the unfolding processes of the Coloured PetriNets that control the execution of a transactional composite Web service are checkpointed if a fault occurs. In such way, users can first get partial responses as soon as they are obtained, and the composite service can be restarted from an advanced point of execution.…”

Dynamic recovery decision during composite web services execution

“…However, checkpointing techniques can be implemented to relax the all-or-nothing transactional property and still provide fault tolerance [15] or can be implemented as an alternative technique independent of transactional properties [3,20]. In both cases, when a failure occurs, snapshots that contain advanced execution state (including partial results) are taken and can be returned to the user.…”

“…Then, checkpointing techniques can be implemented to relax the all-or-nothing property and still provide fault tolerance [3,15,20]. Snapshots that contain advanced execution state (including partial results) are taken and can be returned to the user.…”

“…The faulty CWS can be restarted from an advanced point of execution (snapshot) to complete the desired result. Previous works also use chekpointing techniques [15]. As roll-back techniques, chekpointing demands persistent storage to keep the snapshots.…”