High-Level
Services
Proxies
Agents
MonALISA
Network of
Lookup Services
routing, control, and optimization for
large-scale data transfers on dedicated circuits, data-transfer scheduling,
distributed job scheduling, and automated management of remote services among a large set of grid facilities.
The initial design of the MonALISA
system was inspired by the Jini architecture. 10 MonALISA is designed as an
ensemble of autonomous self-describing agent-based subsystems that are
registered as dynamic services. These
services are able to collaborate and
cooperate in performing a wide range
of distributed information-gathering
and processing tasks.
The MonALISA architecture, schematically presented in Figure 1, is based
on four layers of global services. The en-
tire system is based on Java technology. 9
The first layer is the lookup services
(LUS) network that provides dynamic
registration and discovery for all other
services and agents. MonALISA services are able to discover each other in
the distributed environment and to be
discovered by interested clients. The
registration uses a lease mechanism. If
a service fails to renew its lease, it is removed from the LUS and a notification
is sent to all the services or other applications that subscribed to such events.
The second layer of the MonALISA
framework represents the network
of MonALISA services. They provide
the multithreaded execution engine
that accommodates many monitoring
modules and a variety of loosely cou-
pled agents that analyze the collected
information in real time. The framework also integrates a set of existing
monitoring tools and procedures to
collect parameters describing computational nodes, applications, and
network performance. The collected
information can be stored locally
in databases. Dynamically loadable
agents and filters are able to process
information locally and communicate
with other services or agents in order
to perform global optimization tasks.
A service in the MonALISA framework
is a component that interacts autonomously with other services either
through dynamic proxies or via agents
that use self-describing protocols. By
using the network of lookup services,
