DESIGN AND IMPLEMENTATION OF A DISTRIBUTED MONITOR FACILITY

There are four major drawbacks to use existing mechanisms, such as whi ch are provided by Mach and Masscomp, etc., for designing monitors. (1 ) They cannot support fault-tolerance. (2) They are tailor-made for sp ecific kernels. (3) They cannot directly be applied in distributed env ironments. (4) Users must have good backgrounds in handling light-weig ht processes. In this paper, we present a distributed monitor facility , called DISMON, that supports the mechanisms needed to design monitor s and makes them fault tolerant to hardware failures. At the same time , monitors are constructed at the application level not kernel level s uch that they are portable and easily designed. In order to produce a monitor, the source monitor program, which makes use of a C-like langu age to code it in the DISMON, is pre-compiled by a monitor generation program, called MONGEN, to generate it. The monitor procedure calls ar e made entirely transparent by means of an agent based name server tha t helps callers to obtain the address of a monitor. The interface betw een callers and monitor are similar to the Sun's Remote Procedure Call (RPC) mechanism, but the RPC servers have been replaced by monitors.