HCloud, a Healthcare-Oriented Cloud System with Improved Efficiency in Biomedical Data Processing - Cloud Computing with e-Science Applications - page 173

8.2.4 Key Components Implementation in HCloud
There are three key components addressed here:
• The MQ is a kind of component that provides an asynchronous
communication protocol to achieve independence between the mes-
sage sender and the receiver. The queue is utilized for storing the
event message generated by a sender (publisher), and all of the lis-
teners (subscribers) who are interested in this kind of event can fetch
this message to process a predefined routine. All communication
parties should follow the same protocol (e.g., advanced MQ protocol)
and utilize an available MQ API [16] to operate the queue. It is not nec-
essary that two parties must know each other exists. After a message
is inserted into a queue, it will be preserved and not deleted from
the MQ until the corresponding subscriber reconnects to the system.
Messages can be exchanged on the process, application, or even inter-
cloud level. The queue resides in the cloud just as an engine to drive
the system. In addition, different message heads identify the analysis
algorithm and indicate the subsequent behaviors of the cloud.
• The plug-in algorithm framework is developed with respect to the extend-
ability of various services, which is based on the publish/subscribe
mechanism to provide customized functions conveniently, not only
for health care but also for other services. The whole system can
reduce the module coupling by adopting this algorithm. For instance,
various data-mining algorithms, such as analysis of peripheral vas-
cular function, instantaneous heart rate, chaotic characteristics of
the power spectral density, and so on, should be adopted to perform
automatically according to different analyzed signals. Every differ-
ent function can subscribe to the different themes of the message,
which is classified by a message head. In other words, using such
Publish/Subscribe mechanisms, different mining functions can be
called on by listening to the corresponding types of message the func-
tion is interested in. Accordingly, we designed an abstract core class
named the CoreStubClass , including a private attribute analysisKind
and an abstract method handleRequest(int) . This class communicates
with Message via MQ, and the other kinds of concrete implementation
classes extended the CoreInterface (e.g., SignalFilterCore , ECGAnalysisCore
and other data-mining classes). Figure 8.5 shows the class framework of
the plug-in algorithm.
• Distributed storage is the basis of cloud storage. The structural model
of cloud storage is composed of four layers: the storage layer, the
platform management layer, the application interface, and the access
layer, as shown in Figure 8.6.
The core layer is the platform management layer, which ensures the reli-
able storage and efficient access of the large amounts of semistructured or