Pattern-Oriented Software Architecture Volume 3: Patterns for Resource Management

2 Resource Acquisition

“I find that a great part of the information I have was acquired by looking up something and finding something else on the way.”

Franklin P. Adams

The lifecycle of a resource begins with its acquisition. How and when resources are acquired can play a critical role in the functioning of a software system. By optimizing the time it takes to acquire resources, system performance can be significantly improved.

Before a resource can be acquired, the most fundamental problem to be solved is how to find a resource. The Lookup (21) pattern addresses this problem and describes how resources can be made available by resource providers, and how these resources can be found by resource users.

Once a resource has been found, it can be acquired. The timing of resource acquisition is important, and is mainly addressed by Lazy Acquisition (38) and Eager Acquisition (53). While Lazy Acquisition defers acquisition of resources to the latest possible point in time, Eager Acquisition instead strives to acquire resources as early as possible. Both extremes are important and are heavily dependent on the use of the resources.

If resources that are acquired are not used immediately it can lead to their wastage. Lazy Acquisition addresses this problem and consequently leads to better system scalability. On the other hand, some systems have real-time constraints and stringent requirements for the timing of resource acquisition. Eager Acquisition addresses this problem, and consequently ...