Information Technology Reference
In-Depth Information
4 The mOSAIC Solution: Cloud Agency
The EC-FP7-ICT mOSAIC project [7] intends to improve the state-of-the-art in
Cloud computing by creating, promoting and exploiting an open-source Cloud
application programming interface and a platform targeted for developing multi-
Cloud oriented applications. Cloud Agency represents the mOSAIC solution for
provisioning and management of Cloud resources that allows for the deployment
and execution of the mOSAIC platform and applications.
Cloud Agency [12] is a multi agent system that accesses, on behalf of the user,
the utility market of Cloud computing to maintain always the best configuration
of resources, to satisfy the application requirements. It supplements the common
management functionalities, which are currently provided by Cloud infrastruc-
tures, with new advanced services, by implementing transparent layer to IAAS
Private and Public Cloud services.
Agents can be orchestrated by invoking those services, which are offered by
Cloud Agency through an OCCI compliant RESTFull interface, according to the
workflow defined in Section 3.
One of the leading agents that composes Cloud Agency is the
Broker Agent
that receives the list of those resources that the mOSAIC application needs for its
deployment and execution, asks to providers for available offers, brokers the best
one and allows for closing the transaction.
Vendor Agents
implement a wrapper
for a specific Cloud: they are used to get an offer for resource provisioning, to
accept or refuse that offer, to get informations about a resource or to perform
an action on it (start, stop, resume). About Cloud monitoring,
Meter Agents
perform measures of performance indexes at IAAS level and return their values to
the
Archiver Agent
. The Archiver collects the measures and maintains statistics
about the mOSAIC system. For the reconfiguration service the
Tier Agent
has
been developed: it is triggered by the Archiver and uses policies defined by
the user to apply the necessary reactions. The
Mediator Agent
receives requests
directly from the user: it is in charge of starting new transactions for provisioning
by creating Broker agents; it also starts new Tiers and Meters, and returns
information about Cloud Agency configuration and services.
Being implemented as a MAS (Multi Agent System), the internal work-flow of
the agency is intrinsically asynchronous because agents react on the occurrence of
an incoming message. In the same way RESTFull APIs of Cloud Agency have been
conceived for an event-driven mOSAIC programming model. Asynchronous Ser-
vice Requests (ASR) are used to ask Cloud Agency for something to be executed.
For example to start a negotiation, to accept or to refuse the SLA, to start a VM,
etc. Requests, as any other action, are not-blocking. It means that execution is
started remotely, but the client can continue to run. On the other hand, requests
will generatefuture events, which have to be handled by the requester. By the same
way, asynchronous events from Cloud Agency are notified to the Cloud user. Syn-
chronous Service Requests (SSR) are used to get informations. For example clients
can ask for reading an SLA or the status of a negotiation, to get the list of vendors
or the list of the resources. Queries are synchronous, they return immediately the
response if it is available, and an exception otherwise.
