Top Related Projects
Build highly concurrent, distributed, and resilient message-driven applications on the JVM
Asynchronous, Reactive Programming for Scala and Scala.js.
The pure asynchronous runtime for Scala
ZIO — A type-safe, composable library for async and concurrent programming in Scala
Wonderful reusable code from Twitter
Quick Overview
The scala/scala-async
project is a library that provides support for asynchronous programming in Scala. It allows developers to write asynchronous code using a synchronous-looking syntax, making it easier to reason about and manage concurrent operations.
Pros
- Improved Readability: The async/await syntax provided by the library makes asynchronous code more readable and easier to understand, compared to traditional callback-based approaches.
- Seamless Integration: The library integrates well with the Scala language and ecosystem, allowing developers to use it alongside other Scala features and libraries.
- Flexibility: The library supports a variety of asynchronous primitives, including Futures, Promises, and Actors, making it versatile for different use cases.
- Reduced Complexity: The library helps to reduce the complexity of asynchronous code, making it easier to write, maintain, and reason about.
Cons
- Dependency on Scala: The library is tightly coupled with the Scala language and may not be as useful for developers working in other JVM-based languages.
- Limited Adoption: While the library is well-designed and useful, it has not seen as widespread adoption as some other asynchronous programming libraries in the Scala ecosystem.
- Potential Performance Overhead: The library's use of macros and code transformation may introduce some performance overhead, which may be a concern for certain high-performance applications.
- Compatibility Challenges: The library has undergone several major version changes, which may introduce compatibility issues for existing projects.
Code Examples
Here are a few examples of how to use the scala/scala-async
library:
Asynchronous Function
import scala.async.Async.{async, await}
import scala.concurrent.Future
def fetchData(): Future[String] = async {
val result = await(Future.successful("Hello, Async!"))
result
}
This example demonstrates how to define an asynchronous function using the async
and await
constructs provided by the library.
Parallel Execution
import scala.async.Async.{async, await}
import scala.concurrent.Future
def fetchData1(): Future[String] = async {
await(Future.successful("Data 1"))
}
def fetchData2(): Future[String] = async {
await(Future.successful("Data 2"))
}
def fetchAllData(): Future[(String, String)] = async {
val (data1, data2) = await(fetchData1(), fetchData2())
(data1, data2)
}
This example shows how to execute multiple asynchronous operations in parallel using the await
construct.
Error Handling
import scala.async.Async.{async, await}
import scala.concurrent.Future
import scala.util.{Failure, Success}
def fetchData(): Future[String] = async {
try {
await(Future.successful("Hello, Async!"))
} catch {
case e: Exception =>
println(s"Error: $e")
throw e
}
}
This example demonstrates how to handle errors in asynchronous code using the try-catch
construct within the async
block.
Getting Started
To use the scala/scala-async
library in your Scala project, you can add the following dependency to your build.sbt
file:
libraryDependencies += "org.scala-lang.modules" %% "scala-async" % "0.9.7"
Once you have the library added, you can start using the async
and await
constructs in your code, as shown in the examples above.
For more detailed information on using the library, you can refer to the project's README and the official documentation.
Competitor Comparisons
Build highly concurrent, distributed, and resilient message-driven applications on the JVM
Pros of Akka
- Comprehensive actor-based concurrency model for distributed systems
- Supports various patterns like clustering, persistence, and streams
- Large ecosystem with extensive documentation and community support
Cons of Akka
- Steeper learning curve due to its extensive feature set
- Heavier runtime overhead compared to lightweight async operations
- More complex setup and configuration for smaller projects
Code Comparison
Scala-async:
async {
val f1 = async { ... }
val f2 = async { ... }
await(f1) + await(f2)
}
Akka:
class MyActor extends Actor {
def receive = {
case "message" => sender() ! "response"
}
}
val system = ActorSystem("MySystem")
val actor = system.actorOf(Props[MyActor], "myactor")
Key Differences
- Scala-async focuses on simplifying asynchronous programming within a single JVM
- Akka provides a full-fledged toolkit for building distributed, resilient systems
- Scala-async uses macro-based transformations, while Akka relies on the actor model
- Akka offers more advanced features like clustering and persistence
- Scala-async is more suitable for simpler async scenarios, while Akka excels in complex distributed environments
Both libraries have their merits, and the choice depends on the specific requirements of your project, its scale, and the complexity of concurrency needs.
Asynchronous, Reactive Programming for Scala and Scala.js.
Pros of Monix
- More comprehensive and feature-rich, offering a wide range of reactive programming tools
- Better performance and scalability for complex asynchronous operations
- Active development and maintenance with frequent updates
Cons of Monix
- Steeper learning curve due to its extensive API and concepts
- Potentially overkill for simple asynchronous tasks
- Larger dependency footprint in projects
Code Comparison
Scala-async:
async {
val f1 = async { ... }
val f2 = async { ... }
await(f1) + await(f2)
}
Monix:
Task.parMap2(
Task { ... },
Task { ... }
)(_ + _)
Summary
Scala-async provides a simpler, more straightforward approach to handling asynchronous operations in Scala, focusing primarily on async/await syntax. It's easier to learn and use for basic asynchronous tasks.
Monix, on the other hand, offers a more comprehensive toolkit for reactive and asynchronous programming. It provides better performance and scalability for complex scenarios but comes with a steeper learning curve.
Choose Scala-async for simpler projects or when getting started with asynchronous programming in Scala. Opt for Monix when building more complex, reactive systems that require advanced features and optimized performance.
The pure asynchronous runtime for Scala
Pros of cats-effect
- Provides a more comprehensive and flexible approach to functional concurrency
- Offers a rich ecosystem of libraries and integrations
- Supports a wider range of effect types and abstractions
Cons of cats-effect
- Steeper learning curve due to its more complex and abstract nature
- May introduce additional overhead for simpler use cases
- Requires more boilerplate code for basic operations
Code Comparison
scala-async:
async {
val f1 = async { ... }
val f2 = async { ... }
await(f1) + await(f2)
}
cats-effect:
for {
fiber1 <- IO.async_ { ... }.start
fiber2 <- IO.async_ { ... }.start
result1 <- fiber1.join
result2 <- fiber2.join
} yield result1 + result2
Summary
scala-async provides a simpler, more straightforward approach to handling asynchronous operations, making it easier to use for developers familiar with traditional synchronous code. It's particularly useful for basic async scenarios.
cats-effect, on the other hand, offers a more powerful and flexible toolkit for managing concurrency and effects in functional programming. It provides a wider range of features and abstractions, making it suitable for more complex applications and advanced use cases.
The choice between the two depends on the specific requirements of the project, the team's familiarity with functional programming concepts, and the desired level of control over concurrency and effects.
ZIO — A type-safe, composable library for async and concurrent programming in Scala
Pros of ZIO
- More comprehensive and feature-rich ecosystem for functional effects
- Better performance and resource management
- Stronger type safety and error handling capabilities
Cons of ZIO
- Steeper learning curve due to its more complex API
- Potentially overkill for simpler asynchronous tasks
- Requires more boilerplate code for basic operations
Code Comparison
scala-async:
async {
val f1 = async { ... }
val f2 = async { ... }
await(f1) + await(f2)
}
ZIO:
for {
f1 <- ZIO.async { ... }
f2 <- ZIO.async { ... }
result <- ZIO.succeed(f1 + f2)
} yield result
Summary
scala-async provides a simpler, more lightweight approach to handling asynchronous operations in Scala, focusing primarily on async/await syntax. It's easier to learn and use for basic tasks but lacks advanced features.
ZIO offers a more comprehensive solution for functional effect management, with better performance and stronger type safety. However, it comes with a steeper learning curve and may be excessive for simpler use cases.
The choice between the two depends on project requirements, team expertise, and the complexity of asynchronous operations needed in the application.
Wonderful reusable code from Twitter
Pros of util
- Broader utility library with a wide range of features beyond async operations
- More actively maintained with frequent updates and contributions
- Extensive documentation and examples for various use cases
Cons of util
- Larger dependency footprint due to its comprehensive nature
- Steeper learning curve for developers new to the Twitter ecosystem
- May include unnecessary features for projects only needing async functionality
Code Comparison
scala-async:
async {
val f1 = async { ... }
val f2 = async { ... }
await(f1)
await(f2)
}
util:
import com.twitter.util.Future
val f1 = Future { ... }
val f2 = Future { ... }
Future.join(f1, f2)
Summary
scala-async focuses specifically on asynchronous programming in Scala, providing a more lightweight and targeted solution. It offers a simpler API for handling async operations using async
and await
constructs.
util, on the other hand, is a comprehensive utility library that includes async functionality along with many other features. It provides a broader set of tools and abstractions for building scalable applications, particularly within the Twitter ecosystem.
The choice between the two depends on project requirements, existing dependencies, and the need for additional utilities beyond async programming.
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scala-async
A Scala DSL to enable a direct style of coding when composing Future
s.
Usage
As of scala-async 1.0, Scala 2.12.12+ or 2.13.3+ are required.
Add dependency
SBT Example
libraryDependencies += "org.scala-lang.modules" %% "scala-async" % "1.0.1"
libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value % Provided
For Maven projects add the following to your
Maven Example
<dependency>
<groupId>org.scala-lang.modules</groupId>
<artifactId>scala-async_2.13</artifactId>
<version>1.0.1</version>
</dependency>
<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-reflect</artifactId>
<version>2.13.8</version>
<scope>provided</scope>
</dependency>
Enable compiler support for async
Add the -Xasync
to the Scala compiler options.
SBT Example
scalacOptions += "-Xasync"
Maven Example
<project>
...
<plugin>
<groupId>net.alchim31.maven</groupId>
<artifactId>scala-maven-plugin</artifactId>
<version>4.4.0</version>
<configuration>
<args>
<arg>-Xasync</arg>
</args>
</configuration>
</plugin>
...
</project>
Start coding
import scala.concurrent.ExecutionContext.Implicits.global
import scala.async.Async.{async, await}
val future = async {
val f1: Future[Boolean] = async { ...; true }
val f2 = async { ...; 42 }
if (await(f1)) await(f2) else 0
}
What is async
?
async
marks a block of asynchronous code. Such a block usually contains
one or more await
calls, which marks a point at which the computation
will be suspended until the awaited Future
is complete.
By default, async
blocks operate on scala.concurrent.{Future, Promise}
.
The system can be adapted to alternative implementations of the
Future
pattern.
Consider the following example:
def slowCalcFuture: Future[Int] = ... // 01
def combined: Future[Int] = async { // 02
await(slowCalcFuture) + await(slowCalcFuture) // 03
}
val x: Int = Await.result(combined, 10.seconds) // 05
Line 1 defines an asynchronous method: it returns a Future
.
Line 2 begins an async
block. During compilation,
the contents of this block will be analyzed to identify
the await
calls, and transformed into non-blocking
code.
Control flow will immediately pass to line 5, as the
computation in the async
block is not executed
on the caller's thread.
Line 3 begins by triggering slowCalcFuture
, and then
suspending until it has been calculated. Only after it
has finished, we trigger it again, and suspend again.
Finally, we add the results and complete combined
, which
in turn will release line 5 (unless it had already timed out).
It is important to note that while lines 1-4 are non-blocking, they are not parallel. If we wanted to parallelize the two computations, we could rearrange the code as follows:
def combined: Future[Int] = async {
val future1 = slowCalcFuture
val future2 = slowCalcFuture
await(future1) + await(future2)
}
Limitations
await
must be directly in the control flow of the async expression
The await
cannot be nested under a local method, object, class or lambda:
async {
List(1).foreach { x => await(f(x) } // invalid
}
await
must be not be nested within try
/ catch
/ finally
.
This implementation restriction may be lifted in future versions.
Comparison with direct use of Future
API
This computation could also be expressed by directly using the higher-order functions of Futures:
def slowCalcFuture: Future[Int] = ...
val future1 = slowCalcFuture
val future2 = slowCalcFuture
def combined: Future[Int] = for {
r1 <- future1
r2 <- future2
} yield r1 + r2
The async
approach has two advantages over the use of
map
and flatMap
:
- The code more directly reflects the programmer's intent,
and does not require us to name the results
r1
andr2
. This advantage is even more pronounced when we mix control structures inasync
blocks. async
blocks are compiled to a single anonymous class, as opposed to a separate anonymous class for each closure required at each generator (<-
) in the for-comprehension. This reduces the size of generated code, and can avoid boxing of intermediate results.
Top Related Projects
Build highly concurrent, distributed, and resilient message-driven applications on the JVM
Asynchronous, Reactive Programming for Scala and Scala.js.
The pure asynchronous runtime for Scala
ZIO — A type-safe, composable library for async and concurrent programming in Scala
Wonderful reusable code from Twitter
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Introducing Visual Copilot: A new AI model to turn Figma designs to high quality code using your components.
Try Visual Copilot