Launch and Async Coroutines in Kotlin Programming Language

Introduction to Launch and Async Coroutines in Kotlin Programming Language

Kotlin’s approach to asynchronous programming is built around the concept of coroutines, which allow developers to write non-blocking code in a more sequential and intuitive man

ner. Among the many coroutine builders Kotlin provides, launch and async are two of the most commonly used. This article will explore both of these builders, their purposes, and how to use them effectively in your applications.

Understanding Coroutines

Before diving into launch and async, it’s essential to understand what coroutines are. Coroutines are lightweight threads that allow you to perform asynchronous programming without the complexity of traditional threading. They can be suspended and resumed without blocking the thread, making them a powerful tool for handling operations that would otherwise block the main thread, such as network calls or heavy computations.

Coroutine Builders: Launch and Async Coroutines in Kotlin Programming Language

Kotlin provides several coroutine builders, among which launch and async are the most popular. Both serve different purposes, and understanding when to use each is crucial for effective coroutine management.

1. Launch Coroutine

The launch builder is used to create a new coroutine that does not return a result. Instead, it fires off a task and continues executing the rest of the code immediately. It is often used for tasks that perform operations without needing a result, such as updating the UI or performing background work.

Basic Syntax

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch {
        // Code to be executed in the coroutine
        println("Starting a coroutine")
        delay(1000) // Simulates a long-running task
        println("Coroutine completed")
    }
    
    println("Main function continues executing")
}

Explanation:

1. runBlocking: This function is used to create a coroutine that blocks the current thread until its execution completes. It is commonly used in the main function for demo purposes.
2. Launch: Inside the runBlocking block, we call launch, which starts a new coroutine. This coroutine runs concurrently with the main function.
3. Delay: The delay function suspends the coroutine for the specified time without blocking the main thread. During this time, the main function continues executing.
4. Output Order: The output will show that the main function continues executing while the coroutine is still running, demonstrating the non-blocking nature of coroutines.

2. Async Coroutine

The async builder is used for coroutines that are expected to return a result. It is ideal for performing parallel computations or network requests where you want to gather results later. When using async, you will get a Deferred object, which represents a future result of the coroutine.

Basic Syntax

import kotlinx.coroutines.*

fun main() = runBlocking {
    val deferredResult = async {
        // Code to be executed in the coroutine
        println("Fetching data...")
        delay(1000) // Simulates a long-running task
        "Data fetched"
    }

    // You can do other work here while the async task is running
    println("Main function continues executing")

    // Wait for the result of the async operation
    val result = deferredResult.await() // This will suspend until the result is available
    println(result)
}

Explanation:

1. Deferred: The async function returns a Deferred object. This object represents a computation that may be completed in the future.
2. Await: To get the result from the async coroutine, you call the await() method on the Deferred object. This suspends the current coroutine until the result is ready.
3. Concurrent Execution: The main function can continue executing while the async coroutine runs. This allows you to perform multiple tasks concurrently.

Use Cases for Launch and Async

When to Use Launch

• Fire-and-Forget Tasks: Use launch for tasks where you don’t need to return a value. For example, updating the UI after a background operation or logging information.
• Independent Tasks: When the coroutine’s execution does not depend on the result of another coroutine, launch is a suitable choice.

When to Use Async

• Tasks That Return Values: Use async when you need the result of the computation, such as fetching data from a network or performing a calculation.
• Concurrent Results: When you have multiple computations that can be done in parallel, async allows you to run them concurrently and collect their results.

Example: Combining Launch and Async

You can combine both launch and async within the same coroutine scope to perform multiple tasks concurrently, some of which may return results, and others that do not.

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch {
        // Fire-and-forget task
        println("Starting background task")
        delay(1000)
        println("Background task completed")
    }

    val result1 = async {
        println("Fetching data 1...")
        delay(1500)
        "Data 1 fetched"
    }

    val result2 = async {
        println("Fetching data 2...")
        delay(2000)
        "Data 2 fetched"
    }

    // Main function continues executing
    println("Main function is still running...")

    // Await the results of async tasks
    println(result1.await())
    println(result2.await())
}

Explanation:

1. Multiple Async Calls: In this example, two async calls fetch data concurrently. While they are running, the main function continues executing.
2. Completion Order: The order of completion of the async tasks may vary, demonstrating the concurrent nature of coroutines.
3. Combining Results: After both async calls complete, their results are printed, showcasing how await() retrieves values from the asynchronous computations.

Advantages of Launch and Async Coroutines in Kotlin Programming Language

Kotlin coroutines, especially the launch and async builders, provide the developer with very strong tools that handle asynchronous programming and concurrency. The benefits of using launch and async coroutines in Kotlin are described in detail below:

1. Simplified Asynchronous Programming

The approach makes asynchronous programming less cumbersome to write and easier to manage .

• Easier syntax: The syntax is cleaner and better to read compared to the traditional callback-based approaches, thus reducing the amount of code.
• Sequential logic: Developers can write asynchronous code in a sequential fashion which, therefore makes the flow of execution easier to understand.

2. Structured Concurrency

Coroutines support structured concurrency, allowing developers to better manage coroutines and their lifecycle.

• Lifecycle management: Whenever a coroutine is launched within a scope (eg. CoroutineScope), it will automatically get cancelled as when the scope gets cancelled which can prevent memory leaks and whatnot.
• Error propagation: exceptions thrown in coroutines can be propagated up the coroutine hierarchy, allowing for centralised error handling.

3. Concurrent Execution using async

The async coroutine builder allows for concurrent execution of multiple tasks. This tends to improve performance where parallelism is actually worthwhile.

• Deferred results: async returns a Deferred object which makes possible retrieving the result once ready, which is particularly handy for a number of independent operations.
• Efficient Resource Utilization: The execution time for parallelizable operations will be reduced much more by the concurrent execution of tasks using async than without.

4. Lightweight and Efficient

Coroutines are much lighter than regular threads; hence, a much better resource utilization is achieved.

• Minimum overhead: Using coroutines for creating and managing them was much lighter than using regular thread management, with thousands running concurrently.
• Scalable: Coroutines hold a lot of promise in many concurrent operations that can scale without crippling the system resources of use in applications that have a high degree of concurrency.

5. Good Cancellation Support

Coroutines offers pretty good cancellation support and assist developers to actually manage long-running tasks.

• Cooperative cancellation: Coroutines should allow cooperative cancellation, so a task can finish cleanly and free up resources properly.
• Structured cancellation: The cancellation of the parent coroutine will automatically cancel all the child coroutines that were launched inside it as well. So, when you cancel a parent coroutine, the structure controls the coroutine lifecycle.

6. Interoperability with Other Libraries

Kotlin coroutines provide excellent interoperability with many libraries and frameworks, making them far easier to use than any other library.

• Compatibility with Android: Android’s Lifecycle Aware Components work well in harmony with Coroutines, enabling better handling of UI updates due to background jobs.
• Hug collaboration: RxJava and Flow Support Besides, coroutines can cooperate with any reactive programming library so that you may take the best of two worlds.

7. Enhanced Readability with launch and async

Readability with launch and async Launch for fire-and-forget and Async for a result lead to much more readable code.

• Clarity in intent: launch clearly shows the coroutine is launched for side effect without an expectation of a result, while async indicates a result is expected improving code readability.
• Reduced debugging: The intent structure of using launch and async could reduce debugging as clearly indicates what purpose each of the coroutines is serving.

8. Better Performance

Effective concurrency can be obtained by both launch and async, which generally contributes to better application performance.

• Non-blocking: These coroutines are designed to be non-blocking in nature so that other coroutines may run while waiting for the result of a task, thus leading to enhanced application responsiveness.
• Optimized usage of threads: They allow the underlying system to optimize its thread usage as the coroutines being suspended and resumed do not require the overhead of a dedicated full thread for every task.

Disadvantages of Launch and Async Coroutines in Kotlin Programming Language

While launch and async coroutine builders of Kotlin significantly outweigh advantages in handling asynchronous programming, these exist with deficits and limitations as well. Knowing such disadvantages is helpful for developers to decide if coroutines are applicable on their application.

1. Overhead for New Developers

Coroutines along with types of launch and async can be difficult for developers who have not practiced asynchronous programming before.

• Learning curve: Mastering understanding of coroutines, its lifecycle, and concurrency management requires fundamental thinking beyond usual synchronous programming.
• Misuse potential: The developers can misuse such builders by such new comer, leading to unexpected behavior or bugs. for example, they do not correctly handle the cancellation of coroutines.

2. Troubleshooting Asynchronous Code

Debugging asynchronous code is harder than non-asynchronous code because of the nature of the execution flow that the nature of using coroutines has on a program.

• Stack traces: When an exception is raised by a coroutine, stack traces may not show where the error actually came from and hence may make debugging harder.
• Concurrency issues: Race conditions and deadlocks can be much more difficult to diagnose in asynchronous code compared to synchronous execution.

3. Resource Overhead Management

Although coroutines are very light, inappropriate management of coroutines may result in overhead.

• Memory leaks: If not cancelled properly, coroutines tend to cause memory leaks because they often keep references to objects that are no longer in need.
• Too many coroutines: Unless managed properly, the creation of too many coroutines might exploit the system resources, and the effectiveness of light coroutines gets lost .

4. Limited Exception Handling

Exception handling in coroutines is less intuitive than in synchronous code.

• Uncaught exceptions: If some exception occurs in a launched coroutine by launch, it will not propagate to the calling code, thus allowing a critical error being actually not handled.
• Different context: Each coroutine has its own context that makes the propagating of exceptions to be complicated and also requires additional error handling logic.

5. Overheads on Performance in Certain Situations

Even though coroutines are generally efficiency-oriented, there may be a performance overhead in certain situations.

• Context switching: If coroutines switch contexts too much, that can result in performance bottlenecks if they contain expensive operations or suspend very frequently.
• Async vs. launch: Being overzealous with async instead of where a plain launch would do incurs code bloat and potential performance deterioration.

6. Not Suitable for CPU-Intensive Activities

Though coroutines are cool with I/O-bound activities, they might not be ideal with CPU-bound activities.

• Blocking operations: If a coroutine performs CPU-bound operations, then it could block the dispatcher, degrading the performance of other coroutines as well as their responsiveness.
• Thread pool limitations: Depending on what kind of dispatcher you have chosen launching too many CPU-bound coroutines might very quickly exhaust the thread pool and degrade performance.

7. Caveats with Cancellation

Coroutines do support cancellation, but with caveats.

• Co-operative cancellation: Coroutines must implement cancellation behavior whereby they observe the cancel signal but also proactively cancel any coroutines dependent on them, to avoid unexpected behavior when they are supposed to stop.
• Hard cancellation logic: Proper cancellation logic of a complex hierarchy of coroutines may be intricate and sensitive to fine design and testing.