SCache

Key features

• Available for: Scala 2.12.x, 2.13.x, 3.3.0 and later
• Auto loading of missing values
• Expiry of not used records
• Deleting oldest values in case of exceeding max size
• Tagless Final
• Partition entries by hashCode into multiple caches in order to avoid thread contention for some corner cases

Introduction

Cache is a main entry point towards scache library. Most users may want to call Cache#expiring method to get the instance of the trait. The documentation could be found in source code of Cache.scala and also at javadoc.io.

See Setup for more details on how to add the library itself.

Cache.scala

trait Cache[F[_], K, V] {

  def get(key: K): F[Option[V]]

  def getOrElse(key: K, default: => F[V]): F[V]

  /**
    * Does not run `value` concurrently for the same key
    */
  def getOrUpdate(key: K)(value: => F[V]): F[V]

  /**
    * Does not run `value` concurrently for the same key
    * Releasable.release will be called upon key removal from the cache
    */
  def getOrUpdateReleasable(key: K)(value: => F[Releasable[F, V]]): F[V]

  /**
    * @return previous value if any, possibly not yet loaded
    */
  def put(key: K, value: V): F[F[Option[V]]]


  def put(key: K, value: V, release: F[Unit]): F[F[Option[V]]]


  def size: F[Int]


  def keys: F[Set[K]]

  /**
    * Might be an expensive call
    */
  def values: F[Map[K, F[V]]]

  /**
    * @return previous value if any, possibly not yet loaded
    */
  def remove(key: K): F[F[Option[V]]]


  /**
    * Removes loading values from the cache, however does not cancel them
    */
  def clear: F[F[Unit]]
}

SerialMap.scala

trait SerialMap[F[_], K, V] {

  def get(key: K): F[Option[V]]

  def getOrElse(key: K, default: => F[V]): F[V]

  /**
    * Does not run `value` concurrently for the same key
    */
  def getOrUpdate(key: K, value: => F[V]): F[V]

  def put(key: K, value: V): F[Option[V]]

  /**
    * `f` will be run serially for the same key, entry will be removed in case of `f` returns `none`
    */
  def modify[A](key: K)(f: Option[V] => F[(Option[V], A)]): F[A]

  /**
    * `f` will be run serially for the same key, entry will be removed in case of `f` returns `none`
    */
  def update[A](key: K)(f: Option[V] => F[Option[V]]): F[Unit]

  def size: F[Int]

  def keys: F[Set[K]]

  /**
    * Might be an expensive call
    */
  def values: F[Map[K, V]]

  def remove(key: K): F[Option[V]]

  def clear: F[Unit]
}

Setup

Although scache is available on maven central, its dependencies are not. That is why one need to include dependency on https://github.com/evolution-gaming/sbt-artifactory-plugin.

addSbtPlugin("com.evolution" % "sbt-artifactory-plugin" % "0.0.2")

libraryDependencies += "com.evolution" %% "scache" % "5.1.2"

ExpiringCache

Recommendations

• There is no use to make refresh.interval bigger than expireAfterWrite. It's just the waste of resources.
• Touch, despite its name, is not called after refresh.
• expireAfterWrite, despite its name, is calculated from date of creation, not time of update.