AVMON
============
The AVMON library allows the user to create a distributed
availability-monitoring overlay. Its design makes the resulting overlay robust
to selfish nodes that want to report higher than real availability. It is also
robust to nodes that collude to try to alter their reported availability, so
that it is reported to be higher than real. 

A node can be a computer host or any process running in a computer. The AVMON
node simply needs a public global identifier. The current implementation
supports IP number plus Port number as global identifier.

To prevent a node from reporting higher than real availability, self-reporting
of availability is not used. Instead, a set of monitors for each node is
selected following a distributed algorithm. These monitors are chosen randomly
from among all the participating nodes, but in a consistent way. Consistency in
the selection is important, because it allows recording of long-term
availability.

To learn the availability of a node, the system asks that node who its monitors
are, and then each monitor is individually queried. Alternatively, if the node
is offline, and the list of its monitors isn't currently known, we can learn
who the monitors are by asking an online cache (this feature is currently being
implemented).

The monitors mentioned above cannot be arbitrary colluders of the target node.
The monitor selection algorithm is based on a function which is known by all
the nodes.  Thus, anyone in the system can verify that node A is indeed the
monitor of node B.  In other words, if node B says that node A is one of its
monitors, we can verify if this is true or false, to avoid false availability
reports.

AVMON gives its users the liberty to specify how to store the availability at
the monitor, and how to report the availability when answering a query.
(Currently, only the defaults are supported, which are raw storage, and raw
reporting).

AVMON can be used by any application that needs light-weight, scalable,
availability-monitoring, in small- or large-scale distributed systems. Some
examples: P2P/Grid-node availability prediction; availability monitor for
availability-based replica-placement algorithms in distributed file-systems;
process-liveliness monitoring in concurrent applications; availability-based
resource allocation in clusters or P2P systems; availability-based user-credit
allocation in P2P systems.

To learn all the details of the design, analysis, and experimental results,
please read the papers available at the website http://avmon.sf.net.

REQUIREMENTS:
=============

As of now, it requires Linux with GLib-2.0 and OpenSSL libraries (which are
standard part of most Linux distributions).

Support for Win and Mac platforms is planned.

INSTALLATION:
=============

See file INSTALL.

HOW TO USE:
===========

To create an AVMON application #include <avmon/avmon.h>. This header file is
well documented and the calls are easy to understand.

Under mini/ we provide two useful "mini" applications: mini-monitor and
mini-query.  With mini-monitor you can create an AVMON overlay that will do raw
availability-monitoring.  The availability of the nodes in the overlay can be
queried with mini-query, which also allows other AVMON-related properties to be
queried. They are not complex, so their source-code is an easy way to learn how
to take advantage of the AVMON library.

I'm currently working on more documentation :-)

COPYING:
========

The AVMON library is under the LGPLv3. See file COPYING.LESSER.

The applications mini-monitor and mini-query are under the GPLv3. See file
COPYING.


WEBSITE:
========
(main) http://avmon.sf.net

(development) http://sf.net/projects/avmon