JarCastingscala-pool
scala-pool is a Scala library for object pooling. The library provides an API and different pool implementations that allow:
- blocking/non-blocking object acquisition
- object invalidation
- capping the number of pooled objects
- creating new objects lazily, as needed
- health checking
- time-based pool eviction (idle instances)
- GC-based pool eviction (soft and weak references)
- efficient thread-safety
Installation
scala-pool is currently available for Scala 2.13, 2.12, and 2.11, the latest version is 0.4.3.
To use it in an existing SBT project, add the following dependency to your build.sbt:
libraryDependencies += "io.github.andrebeat" %% "scala-pool" % "0.4.3"
The latest snapshot version is also available:
libraryDependencies += "io.github.andrebeat" %% "scala-pool" % "0.5.0-SNAPSHOT"
It might be necessary to add the Sonatype OSS Snapshot resolver:
resolvers += Resolver.sonatypeRepo("snapshots")
Currently, the library has no external dependencies apart from the Java and Scala standard libraries.
JDK7 support
This library relies on features only available in Java 8 (java.util.concurrent.atomic.LongAdder), the versions published on Sonatype are compiled with JDK 8. This library provides support for JVM 7 if it is compiled with JDK 7 (only for Scala 2.11). If you need to use this library on JVM 7 then you should compile and package it yourself.
Usage
The basic usage of the pool is shown below:
import io.github.andrebeat.pool._
// Creating a `Pool[Object]` with a capacity of 2 instances
val pool = Pool(2, () => new Object)
// Acquiring a lease on an object from the pool (blocking if none available)
val lease = pool.acquire()
// Using the lease
lease { o =>
println(o)
}
// The object is returned to the pool at this point
All of the different pool features are exposed in the Pool companion object apply method:
Pool(
capacity: Int, // the maximum capacity of the pool
factory: () => A, // the function used to create new objects in the pool
referenceType: ReferenceType, // the reference type of objects in the pool
maxIdleTime: Duration, // the maximum amount of the time that objects are allowed
// to idle in the pool before being evicted
reset: A => Unit, // the function used to reset objects in the pool
// (called when leasing an object from the pool)
dispose: A => Unit, // the function used to destroy an object from the pool
healthCheck: A => Boolean) // the predicate used to test whether an object is
// healthy and should be used, or destroyed otherwise
It is also possible to get a value from a lease and release it (or invalidate) manually.
import io.github.andrebeat.pool._
// Creating a `Pool[Object]` with a capacity of 2 instances
val pool = Pool(2, () => new Object)
// Getting the value from the lease
val obj = lease.get()
// There are currently no objects on the pool
pool.size
// res0: Int = 0
// But its capacity is 2 (objects are created lazily)
pool.capacity
// res1: Int = 2
// There's 1 live object
pool.live
// res2: Int = 1
// And its currently leased
pool.leased
// res3: Int = 1
// Releasing our lease back to the pool
lease.release
// Its now in the pool waiting to be reused
pool.size
// res4: Int = 1
// Closes this pool, properly disposing of each pooled object and
// releasing any resources associated with the pool
pool.close()
The API is documented in depth in the Scaladoc.
License
scala-pool is licensed under the MIT license. See LICENSE for details.