docs: update object pool

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Ilkka Seppälä committed 2024-05-14 17:44:17 +03:00
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@@ -3,27 +3,27 @@ title: Object Pool
category: Creational category: Creational
language: en language: en
tag: tag:
- Game programming - Game programming
- Performance - Instantiation
- Memory management
- Performance
- Resource management
- Scalability
--- ---
## Also known as ## Also known as
Resource Pool * Resource Pool
## Intent ## Intent
When objects are expensive to create and they are needed only for short periods of time it is The Object Pool design pattern manages a pool of reusable objects, optimizing resource use by recycling objects rather than creating and destroying them repeatedly.
advantageous to utilize the Object Pool pattern. The Object Pool provides a cache for instantiated
objects tracking which ones are in use and which are available.
## Explanation ## Explanation
Real world example Real world example
> In our war game we need to use oliphaunts, massive and mythic beasts, but the problem is that they > In our war game we need to use oliphaunts, massive and mythic beasts, but the problem is that they are extremely expensive to create. The solution is to create a pool of them, track which ones are in-use, and instead of disposing them re-use the instances.
> are extremely expensive to create. The solution is to create a pool of them, track which ones are
> in-use, and instead of disposing them re-use the instances.
In plain words In plain words
@@ -31,8 +31,7 @@ In plain words
Wikipedia says Wikipedia says
> The object pool pattern is a software creational design pattern that uses a set of initialized > The object pool pattern is a software creational design pattern that uses a set of initialized objects kept ready to use – a "pool" – rather than allocating and destroying them on demand.
> objects kept ready to use – a "pool" – rather than allocating and destroying them on demand.
**Programmatic Example** **Programmatic Example**
@@ -65,7 +64,7 @@ public class Oliphaunt {
} }
``` ```
Next we present the `ObjectPool` and more specifically `OliphauntPool`. Next, we present the `ObjectPool` and more specifically `OliphauntPool`.
```java ```java
public abstract class ObjectPool<T> { public abstract class ObjectPool<T> {
@@ -137,11 +136,46 @@ Pool available=0 inUse=3
## Class diagram ## Class diagram
![alt text](./etc/object-pool.png "Object Pool") ![Object Pool](./etc/object-pool.png "Object Pool")
## Applicability ## Applicability
Use the Object Pool pattern when Use the Object Pool pattern when
* The objects are expensive to create (allocation cost). * You need to frequently create and destroy objects, leading to high resource allocation and deallocation costs.
* You need a large number of short-lived objects (memory fragmentation). * The objects are expensive to create and maintain (e.g., database connections, thread pools).
* A fixed number of objects need to be controlled, like in connection pooling.
* Object reuse can significantly improve system performance and resource management.
## Known Uses
* Database connection pooling in Java applications.
* Thread pooling in Java concurrent programming.
* Pooling of socket connections in network applications.
* Object pools in game development for frequently created and destroyed game objects.
## Consequences
Benefits:
* Improved Performance: Reduces the overhead of object creation and garbage collection.
* Resource Management: Controls the number of instances, reducing resource contention and limiting resource usage.
* Scalability: Allows the application to handle more requests by reusing a fixed number of objects.
Trade-offs:
* Complexity: Adds complexity to the codebase, requiring careful management of the pool.
* Thread Safety: Requires careful handling of concurrent access to the pool, introducing potential synchronization issues.
* Initialization Cost: Initial creation of the pool can be resource-intensive.
## Related Patterns
[Singleton](https://java-design-patterns.com/patterns/singleton/): Ensures a single instance of the pool is used, providing a global point of access.
[Flyweight](https://java-design-patterns.com/patterns/flyweight/): Shares fine-grained objects to reduce memory usage, complementing object pooling by managing object state efficiently.
[Factory Method](https://java-design-patterns.com/patterns/factory-method/): Often used to create objects within the pool, abstracting the instantiation process.
## Credits
* [Design Patterns: Elements of Reusable Object-Oriented Software](https://amzn.to/3w0pvKI)
* [Effective Java](https://amzn.to/4cGk2Jz)
* [Java Concurrency in Practice](https://amzn.to/4aRMruW)
@@ -24,11 +24,12 @@
*/ */
package com.iluwatar.object.pool; package com.iluwatar.object.pool;
import java.util.concurrent.atomic.AtomicInteger; import java.util.concurrent.atomic.AtomicInteger;import lombok.extern.slf4j.Slf4j;
/** /**
* Oliphaunts are expensive to create. * Oliphaunts are expensive to create.
*/ */
@Slf4j
public class Oliphaunt { public class Oliphaunt {
private static final AtomicInteger counter = new AtomicInteger(0); private static final AtomicInteger counter = new AtomicInteger(0);
@@ -43,7 +44,7 @@ public class Oliphaunt {
try { try {
Thread.sleep(1000); Thread.sleep(1000);
} catch (InterruptedException e) { } catch (InterruptedException e) {
e.printStackTrace(); LOGGER.error("Error occurred: ", e);
} }
} }