빠르고 정확한 개발자 빠르고 정확한 개발자

scala/basic

• Semaphore 를 사용해 최대 maxConcurrent 개의 Future만 실행되도록 제한

  scala/basic 2025. 3. 13. 10:28

  내가 작성package com.naver.search.webimport java.util.concurrent.Semaphoreimport scala.concurrent.ExecutionContext.Implicits.globalimport scala.concurrent.{Await, Future}object SemaphoreFutureTest { def semFuture[T](f: => T, n: Int): Future[T] = { val sem = new Semaphore(n) Future { try { sem.acquire() f } finally { sem.release() } } } def f(x: Int): Int = { Thread.sleep(1000) pr..

  Read More
• Tagless Final

  scala/basic 2024. 11. 19. 15:09

  https://www.reddit.com/r/scala/comments/s6ih9p/comment/htagml4/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button  trait Expr[T] { def num(n: Int): T def add(l: T, r: T): T}implicit def eval: Expr[Int] = new Expr[Int] { def num(i: Int): Int = i def add(l: Int, r: Int): Int = l + r}implicit def show: Expr[String] = new Expr[String] { def num(i:..

  Read More
• method 이름은 같은데 param, return 타입을 다르게 구현하기

  scala/basic 2024. 3. 7. 17:06

  case class GoogleRaw(content: String, crawlId: String) case class NaverRaw(content: String) case class GoogleParsed(sections: Seq[String], crawlId: String) case class NaverParsed(sections: Seq[String]) trait Cralwer { type Raw type Parsed def fetch(url: String): Raw def parse(raw: Raw): Parsed def save(raw: Raw, parsed: Parsed): Int } object GoogleCrawler extends Cralwer { type Raw = GoogleRaw t..

  Read More
• Blocking Future

  scala/basic 2023. 2. 13. 11:16

  scala-best-practices 의 MUST use Scala's BlockContext on blocking I/O 문서와 SHOULD use a separate thread-pool for blocking I/O 를 참고했을 때, 간편하게 쓴다면 아래처럼 BlockingFuture Helper 를 만드는 것도 좋을 것 같다. import scala.concurrent.{blocking, Future, ExecutionContext} /** * This is an idiomatic way of executing blocking code * Use BlockingFuture(...) instead of normal Future(...) anywhere */ object BlockingFuture {..

  Read More
• Environment, Property variable 읽기

  scala/basic 2023. 2. 3. 15:34

  Environment val myEnv: Option[String] = sys.env.get("MY_ENV") println(myEnv) > export MY_ENV="env_123" > java -cp app.jar ... Property val myProp: Option[String] = sys.props.get("MY_PROP") println(myProp) > java -cp app.jar -DMY_PROP="prop_abc" ...

  Read More
• Future[Try[A]] <=> Future[A] 상호간 변환하기

  scala/basic 2023. 1. 16. 12:58

  Future[Try[A]] Future[A]  변환 Future[Try[A]] => Future[A]import scala.concurrent.ExecutionContext.Implicits.globalimport scala.concurrent.Futureimport scala.util.{Success, Try}object FutureTryTest { def main(args: Array[String]): Unit = { val futureTry: Future[Try[Int]] = Future(Success(1)) // https://github.com/monix/monix/blob/series/3.x/monix-execution/shared/src/main/scala/monix/e..

  Read More
• Error Modeling (with Exception)

  scala/basic 2023. 1. 16. 10:55

  import play.api.libs.json.{Json, OFormat} sealed class HttpError(val status: Int, val message: String) extends Throwable(message) object HttpError { implicit val jsonFormat: OFormat[HttpError] = Json.format[HttpError] def apply(status: Int, message: String): HttpError = new HttpError(status, message) def unapply(err: Throwable): Option[(Int, String)] = err match { case err: HttpError => Option((..

  Read More
• Scala Using

  scala/basic 2022. 12. 19. 00:03

  scala 2.13 버전부터 scala.util.Using 이 추가되었다. cats-effect 의 Resource 또는 zio 의 Scope 처럼 resource 관리를 위해 사용될 수 있다. AutoCloseable Resource 에서 사용 기본적으로 Using.resource(..) 혹은 Using.resources(..) 를 이용하자. (필요하면 Try 로 감싼다) https://www.scala-lang.org/api/2.13.6/scala/util/Using$$Releasable.html 을 보면 아래와 같은 내용이 있다. An instance of Releasable is needed in order to automatically manage a resource with Using. An ..

  Read More