Migrating e-Science Applications to the Cloud: Methodology and Evaluation - Cloud Computing with e-Science Applications - page 92

In this work, we present a vendor- and technology-independent method-
ology for migrating the database layer of applications and refactoring the
application architecture as positioned in existing methodologies for migra-
tion of applications (see Section 5.4). The methodology is applicable to appli-
cations in different application domains and is agnostic to the types of data
sources. It fulfills requirements also presented in this work, which we have
identified in collaboration with software engineers and domain experts in
several research projects. We use this methodology to migrate the database
layer of a scientific workflow management system (SimTech SWfMS), which
we developed in the scope of our research activities in the SimTech project.
The architecture and implementation details of the system, as well as the
motivation for the database layer migration, are first presented in Section 5.2.
The migration of the SimTech SWfMS has been done using the Cloud Data
Migration Support Tool—a proof-of-concept implementation of the method-
ology. Both the introduced methodology and the supporting tool have been
evaluated, and our findings are presented in Section 5.5. Our concluding
remarks and plans for future work are presented in Section 5.6.
5.2 Motivating Scenario
As a motivating scenario from the e-science field, we use the integrated and
interactive SWfMS developed in the context of the SimTech project (Sonntag,
Hahn, and Karastoyanova, 2012; Sonntag and Karastoyanova, 2010). The
SimTech SWfMS is a distributed system based on conventional workflow
technology adapted to the needs of scientific workflows. The main compo-
nents of the SimTech SWfMS are a modeling and monitoring tool, a workflow
engine, an enterprise service bus, an auditing system, a messaging system,
several database management systems, and an application server running
the simulation services.
We present the architecture of the SimTech SWfMS in Figure 5.1. The user
interacts with the system using the modeling and monitoring tool. SimTech
SWfMS provides a graphical user interface to model, execute, and monitor
scientific workflows. When the user initiates the execution of a workflow,
the tool automatically deploys the workflow model on the workflow engine,
which makes the simulation workflow available for use. The workflow can
be instantiated as many times as needed. The instantiation of a scientific
workflow is the beginning of the execution phase of the workflow life cycle.
The workflows executed by the workflow engine describe the ordered
execution of different tasks such as data preparation, computation, or visu-
alization. In our case, these tasks are realized by web services hosted on an
application server. During the execution of a workflow, the workflow engine
navigates along the predefined control flow and also interacts with these