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https://github.com/twitter/util

Wonderful reusable code from Twitter
https://github.com/twitter/util

finagle scala utility

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Wonderful reusable code from Twitter

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# Twitter Util



[![Build Status](https://github.com/twitter/util/workflows/continuous%20integration/badge.svg?branch=develop)](https://github.com/twitter/util/actions?query=workflow%3A%22continuous+integration%22+branch%3Adevelop)

[![Project status](https://img.shields.io/badge/status-active-brightgreen.svg)](#status)

[![Gitter](https://badges.gitter.im/twitter/finagle.svg)](https://gitter.im/twitter/finagle?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)

[![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.twitter/util-core_2.12/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.twitter/util-core_2.12)



A bunch of idiomatic, small, general purpose tools.



See the Scaladoc [here](https://twitter.github.io/util/docs/#com.twitter.util.package)

or check out the [user guide](https://twitter.github.io/util).



## Status



This project is used in production at Twitter (and many other organizations),

and is being actively developed and maintained.



## Releases



[Releases](https://maven-badges.herokuapp.com/maven-central/com.twitter/util_2.12)

are done on an approximately monthly schedule. While [semver](https://semver.org/)

is not followed, the [changelogs](CHANGELOG.rst) are detailed and include sections on

public API breaks and changes in runtime behavior.



## Contributing



We feel that a welcoming community is important and we ask that you follow Twitter's

[Open Source Code of Conduct](https://github.com/twitter/.github/blob/main/code-of-conduct.md)

in all interactions with the community.



The `release` branch of this repository contains the latest stable release of

Util, and weekly snapshots are published to the `develop` branch. In general

pull requests should be submitted against `develop`. See

[CONTRIBUTING.md](https://github.com/twitter/util/blob/release/CONTRIBUTING.md)

for more details about how to contribute.



# Using in your project



An example SBT dependency string for the `util-core` library would look like this:



```scala

val utilCore = "com.twitter" %% "util-core" % "24.5.0"

```



# Units



## Time



```scala

import com.twitter.conversions.DurationOps._



val duration1 = 1.second

val duration2 = 2.minutes

duration1.inMillis // => 1000L

```



## Space



```scala

import com.twitter.conversions.StorageUnitOps._

val amount = 8.megabytes

amount.inBytes // => 8388608L

amount.inKilobytes // => 8192L

```



# Futures



A Non-actor re-implementation of Scala Futures.



```scala

import com.twitter.conversions.DurationOps._

import com.twitter.util.{Await, Future, Promise}



val f = new Promise[Int]

val g = f.map { result => result + 1 }

f.setValue(1)

Await.result(g, 1.second) // => this blocks for the futures result (and eventually returns 2)



// Another option:

g.onSuccess { result =>

  println(result) // => prints "2"

}



// Using for expressions:

val xFuture = Future(1)

val yFuture = Future(2)



for {

  x <- xFuture

  y <- yFuture

} {

  println(x + y) // => prints "3"

}

```



## Future interrupts



Method `raise` on `Future` (`def raise(cause: Throwable)`) raises the interrupt described by

`cause` to the producer of this `Future`. Interrupt handlers are installed on a `Promise`

using `setInterruptHandler`, which takes a partial function:



```scala

val p = new Promise[T]

p.setInterruptHandler {

  case exc: MyException =>

    // deal with interrupt..

}

```



Interrupts differ in semantics from cancellation in important ways: there can only be one

interrupt handler per promise, and interrupts are only delivered if the promise is not yet

complete.



# Object Pool



The pool order is FIFO.



## A pool of constants



```scala

import scala.collection.mutable

import com.twitter.util.{Await, SimplePool}



val queue = new mutable.Queue[Int] ++ List(1, 2, 3)

val pool = new SimplePool(queue)



// Note that the pool returns Futures, it doesn't block on exhaustion.

assert(Await.result(pool.reserve()) == 1)

pool.reserve().onSuccess { item =>

  println(item) // prints "2"

}

```



## A pool of dynamically created objects



Here is a pool of even-number generators. It stores 4 numbers at a time:



```scala

import com.twitter.util.{Future, FactoryPool}



val pool = new FactoryPool[Int](4) {

  var count = 0

  def makeItem() = { count += 1; Future(count) }

  def isHealthy(i: Int) = i % 2 == 0

}

```



It checks the health when you successfully reserve an object (i.e., when the Future yields).



# Hashing



`util-hashing` is a collection of hash functions and hashing distributors (eg. ketama).



To use one of the available hash functions:



```scala

import com.twitter.hashing.KeyHasher



KeyHasher.FNV1_32.hashKey("string".getBytes)

```



Available hash functions are:



```

FNV1_32

FNV1A_32

FNV1_64

FNV1A_64

KETAMA

CRC32_ITU

HSIEH

```



To use `KetamaDistributor`:



```scala

import com.twitter.hashing.{KetamaDistributor, KetamaNode, KeyHasher}



val nodes = List(KetamaNode("host:port", 1 /* weight */, "foo" /* handle */))

val distributor = new KetamaDistributor(nodes, 1 /* num reps */)

distributor.nodeForHash("abc".##) // => client

```



# Time and Duration



Like arithmetic on doubles, `Time` and `Duration` arithmetic is now free of overflows. Instead, they overflow to `Top` and `Bottom` values, which are analogous to positive and negative infinity.



Since the resolution of `Time.now` has been reduced (and is also more expensive due to its use of system time), a new `Stopwatch` API has been introduced in order to calculate durations of time.



It's used simply:



```scala

import com.twitter.util.{Duration, Stopwatch}

val elapsed: () => Duration = Stopwatch.start()

```



which is read by applying `elapsed`:



```scala

val duration: Duration = elapsed()

```



## License



Copyright 2010 Twitter, Inc.



Licensed under the Apache License, Version 2.0: https://www.apache.org/licenses/LICENSE-2.0