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The monitoring package is composed of four other sub-packages. The first is
responsible for the interception of the interactions between the objects
that comprise the applications in the distributed system. Our intention is to
follow the model described in [7]. In this work,
Interceptors, as defined in the CORBA standard [10], are
inserted into the object invocation path. Each time a client invokes a
method of an object, the message corresponding to this invocation is intercepted
and later re-dispatched to the target object. Using interceptors, the system can
extract useful information from each method invocation, storing it in a log
for later analysis by the event evaluator package. Furthermore, each request
can be time-stamped so that one can know when a message invocation request
was received at the server side. The system can also measure the time between
the reception of the message at the server and the dispatching of the response
to the client, which corresponds to the duration of the method execution at the
server.
In addition to monitoring object interactions, it is also important to
monitor the status of distributed resources, such as memory, CPU, disk, and network
connectivity. This is performed by the
resource monitoring package. To implement such monitoring
functionality we propose the use of resource monitoring objects, responsible
for monitoring system specific parameters, such as processor utilization,
in different hosts of the distributed system. The resource monitoring package
notifies the event evaluator
package whenever the operation of such parameters changes significantly.
Yet another interesting aspect related to monitoring is the location of
mobile devices. As described in the Introduction, we believe that location
awareness will play a fundamental role in future distributed computing environments.
We assume that soon most mobile devices will be equipped with
sensors that will allow us to obtain information about their physical location.
Finally, since we are working in a mobile environment, the services
and resources that a user will be able to use vary depending on his(her)
location. So, the monitoring package should also include the functionality for
dynamically discovering resources and services as the user moves from one place
to another, this is performed by the Resource and Service Discovery package.
Currently, we are concentrating our efforts in the design and implementation
of the first two packages of this monitoring infrastructure.
Next: Event Detection and Notification
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Francisco Jose da Silva e Silva
2001-09-24