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async-method-invocation/README.md
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@@ -10,9 +10,7 @@ tag:
## Intent
Asynchronous method invocation is a pattern where the calling thread is not blocked while waiting results of tasks. The
pattern provides parallel processing of multiple independent tasks and retrieving the results via callbacks or waiting
until everything is done.
Asynchronous method invocation is a pattern where the calling thread is not blocked while waiting results of tasks. The pattern provides parallel processing of multiple independent tasks and retrieving the results via callbacks or waiting until everything is done.
## Also known as
@@ -22,29 +20,21 @@ until everything is done.
Real world example
> Launching space rockets is an exciting business. The mission command gives an order to launch and
> after some undetermined time, the rocket either launches successfully or fails miserably.
> Launching space rockets is an exciting business. The mission command gives an order to launch and after some undetermined time, the rocket either launches successfully or fails miserably.
In plain words
> Asynchronous method invocation starts task processing and returns immediately before the task is
> ready. The results of the task processing are returned to the caller later.
> Asynchronous method invocation starts task processing and returns immediately before the task is ready. The results of the task processing are returned to the caller later.
Wikipedia says
> In multithreaded computer programming, asynchronous method invocation (AMI), also known as
> asynchronous method calls or the asynchronous pattern is a design pattern in which the call site
> is not blocked while waiting for the called code to finish. Instead, the calling thread is
> notified when the reply arrives. Polling for a reply is an undesired option.
> In multithreaded computer programming, asynchronous method invocation (AMI), also known as asynchronous method calls or the asynchronous pattern is a design pattern in which the call site is not blocked while waiting for the called code to finish. Instead, the calling thread is notified when the reply arrives. Polling for a reply is an undesired option.
**Programmatic Example**
In this example, we are launching space rockets and deploying lunar rovers.
The application demonstrates the async method invocation pattern. The key parts of the pattern are
`AsyncResult` which is an intermediate container for an asynchronously evaluated value,
`AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that
manages the execution of the async tasks.
The application demonstrates the async method invocation pattern. The key parts of the pattern are`AsyncResult` which is an intermediate container for an asynchronously evaluated value, `AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that manages the execution of the async tasks.
```java
public interface AsyncResult<T> {
@@ -74,8 +64,7 @@ public interface AsyncExecutor {
}
```
`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted
next.
`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted next.
```java
public class ThreadAsyncExecutor implements AsyncExecutor {
@@ -170,16 +159,14 @@ Here's the program console output.
Use the async method invocation pattern when
* When operations do not need to complete before proceeding with the next steps in a program.
* For tasks that are resource-intensive or time-consuming, such as IO operations, network requests, or complex
computations, where making the operation synchronous would significantly impact performance or user experience.
* For tasks that are resource-intensive or time-consuming, such as IO operations, network requests, or complex computations, where making the operation synchronous would significantly impact performance or user experience.
* In GUI applications to prevent freezing or unresponsiveness during long-running tasks.
* In web applications for non-blocking IO operations.
## Known Uses
* Web servers handling HTTP requests asynchronously to improve throughput and reduce latency.
* Desktop and mobile applications using background threads to perform time-consuming operations without blocking the
user interface.
* Desktop and mobile applications using background threads to perform time-consuming operations without blocking the user interface.
* Microservices architectures where services perform asynchronous communications via messaging queues or event streams.
* [FutureTask](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html)
* [CompletableFuture](https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html)
@@ -190,29 +177,21 @@ Use the async method invocation pattern when
Benefits:
* Improved Responsiveness: The main thread or application flow remains unblocked, improving the user experience in GUI
applications and overall responsiveness.
* Better Resource Utilization: By enabling parallel execution, system resources (like CPU and IO) are utilized more
efficiently, potentially improving the application's throughput.
* Improved Responsiveness: The main thread or application flow remains unblocked, improving the user experience in GUI applications and overall responsiveness.
* Better Resource Utilization: By enabling parallel execution, system resources (like CPU and IO) are utilized more efficiently, potentially improving the application's throughput.
* Scalability: Easier to scale applications, as tasks can be distributed across available resources more effectively.
Trade-offs:
* Complexity: Introducing asynchronous operations can complicate the codebase, making it more challenging to understand,
debug, and maintain.
* Resource Management: Requires careful management of threads or execution contexts, which can introduce overhead and
potential resource exhaustion issues.
* Error Handling: Asynchronous operations can make error handling more complex, as exceptions may occur in different
threads or at different times.
* Complexity: Introducing asynchronous operations can complicate the codebase, making it more challenging to understand, debug, and maintain.
* Resource Management: Requires careful management of threads or execution contexts, which can introduce overhead and potential resource exhaustion issues.
* Error Handling: Asynchronous operations can make error handling more complex, as exceptions may occur in different threads or at different times.
Related Patterns:
* [Command](https://java-design-patterns.com/patterns/command/): Asynchronous method invocation can be used to implement
the Command pattern, where commands are executed asynchronously.
* [Observer](https://java-design-patterns.com/patterns/observer/): Asynchronous method invocation can be used to notify
observers asynchronously when a subject's state changes.
* [Promise](https://java-design-patterns.com/patterns/promise/): The AsyncResult interface can be considered a form of
Promise, representing a value that may not be available yet.
* [Command](https://java-design-patterns.com/patterns/command/): Asynchronous method invocation can be used to implement the Command pattern, where commands are executed asynchronously.
* [Observer](https://java-design-patterns.com/patterns/observer/): Asynchronous method invocation can be used to notify observers asynchronously when a subject's state changes.
* [Promise](https://java-design-patterns.com/patterns/promise/): The AsyncResult interface can be considered a form of Promise, representing a value that may not be available yet.
## Credits