ObjectPool

Object pool (Creational)

Improve performance by reusing objects which creation can be significantly expensive

Problem

Object creation is expensive, the number of instances created is high and the number of instantiations in use at any one time is low

Solution

Create a kind of cache to store instances created. Clients request to the pool an instance instead of create a new one by themselves.

The pool has the capacity of creating more instances if required but, if possible, will retrieve an existent and unused instance.

General diagram

Actors

• Reusable. Wraps the limited resource, will be shared by several clients for a limited amount of time.
• Client. Uses an instance of type Reusable.
• ReusablePool Manage the reusable objects for use by Clients, creating and managing a pool of objects.

Considerations

If resources are limited, object pool can have a max. limit of instances to be created.

Related patterns

• Object pool is crated as a Singleton so it can know and manage every instance created.
• While the Prototype pattern helps in improving the performance by cloning the objects, the object pool pattern offers a mechanism to reuse objects that are expensive to create

References

• http://www.oodesign.com/object-pool-pattern.html
• https://sourcemaking.com/design_patterns/object_pool