Gridbus Workflow Enactment Engine - Grid Computing: Infrastructure, Service, and Applications - page 119

• Dispatcher is used to access middleware. Resources may be grid-

enabled by different middleware such as Globus [6] or Web services
[7]. WFEE had been designed to support different middleware by
creating dispatchers for each middleware to support interaction
with resources.
Data movement system enables data transfer between grid nodes

•

by using HTTP and GridFTP [8] protocols.
Workl ow executor is the central component in WFEE. It interacts •

with resource discovery to i nd suitable grid resources at runtime; it
locates a task on resources by using the dispatcher component; it
controls input data transfer between task execution nodes through
data movement .

5.3 Workflow Execution Management
The workl ow execution is managed using a decentralized architecture.
Instead of a central scheduler for handling whole workl ow execution, a
task manager is created for handling the processing of a task or a group of
tasks, including resource discovery and allocation, task dispatcher, and
failure processing. Different scheduling strategies can be deployed in
different task managers (TMs) for resource selection, QoS negotiation, and
data transmission optimization. The lifetimes of TMs, as well as the whole
workl ow execution, are controlled by a workl ow coordinator (WCO).
As shown in Figure 5.2, dedicated TMs are created by WCO for each task
group. Each TM has its own monitor, which is responsible for monitoring
the health of the task execution on the remote node. Every TM maintains a
resource group, which is a set of resources that provides services required

Workflow
coordinator

Task manager
factory

Scheduling
strategy

Event
service

Task manager

Resource
group

Tasks

Monitor

Workflow execution management

FIGURE 5.2 Execution management.