Automated online monitoring of distributed applications through external monitors

It is a challenge to provide detection facilities for large-scale distributed systems running legacy code on hosts that may not allow fault tolerant functions to execute on them. It is tempting to structure the detection in an observer system that is kept separate from the observed system of protocol entities, with the former only having access to the latter´s external message exchanges. In this paper, we propose an autonomous self-checking monitor system, which is used to provide fast detection to underlying network protocols. The monitor architecture is application neutral and, therefore, lends itself to deployment for different protocols, with the rulebase against which the observed interactions are matched, making it specific to a protocol. To make the detection infrastructure scalable and dependable, we extend it to a hierarchical monitor structure. The Monitor structure is made dynamic and reconfigurable by designing different interactions to cope with failures, load changes, or mobility. The latency of the monitor system is evaluated under fault free conditions, while its coverage is evaluated under simulated error injections