Ecosyste.ms: Awesome
An open API service indexing awesome lists of open source software.
https://github.com/timwspence/cats-stm
A STM implementation for Cats Effect
https://github.com/timwspence/cats-stm
cats cats-effect functional-programming monad scala software-transactional-memory transactional-memory
Last synced: 1 day ago
JSON representation
A STM implementation for Cats Effect
- Host: GitHub
- URL: https://github.com/timwspence/cats-stm
- Owner: TimWSpence
- License: apache-2.0
- Created: 2019-04-24T11:24:40.000Z (over 5 years ago)
- Default Branch: main
- Last Pushed: 2024-12-02T10:28:20.000Z (20 days ago)
- Last Synced: 2024-12-14T03:07:35.137Z (9 days ago)
- Topics: cats, cats-effect, functional-programming, monad, scala, software-transactional-memory, transactional-memory
- Language: Scala
- Homepage: https://timwspence.github.io/cats-stm/
- Size: 6.21 MB
- Stars: 145
- Watchers: 7
- Forks: 17
- Open Issues: 11
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE.txt
- Code of conduct: CODE_OF_CONDUCT.md
Awesome Lists containing this project
README
# Cats STM
[](https://github.com/TimWSpence/cats-stm/actions?query=workflow%3A%22Continuous+Integration%22)
[](https://index.scala-lang.org/timwspence/cats-stm/cats-stm)
[](https://discord.gg/QNnHKHq5Ts)
[](https://scala-steward.org)
Composable in-memory transactions for [Cats
Effect](https://typelevel.org/cats-effect/) which will handle locking,
optimistic concurrency and automatic retries for you. The STM runtime takes care
of acquiring locks in the correct order so your transactions are safe and should
not deadlock. This locking is optimistic so it will only acquire the minimal set
of locks and only when necessary to commit the result of a transaction.
For more information, see the
[microsite](https://timwspence.github.io/cats-stm/).
### Example
```scala
import scala.concurrent.duration._
import cats.effect.{IO, IOApp}
import io.github.timwspence.cats.stm.__
object Main extends IOApp.Simple {
override def run: IO[Unit] = STM.runtime[IO].flatMap(run(_))
def run(stm: STM[IO]): IO[Unit] = {
import stm._
def transfer(accountForTim: TVar[Long], accountForSteve: TVar[Long]): IO[Unit] =
stm.commit {
for {
balance <- accountForTim.get
_ <- stm.check(balance > 100)
_ <- accountForTim.modify(_ - 100)
_ <- accountForSteve.modify(_ + 100)
} yield ()
}
def giveTimMoreMoney(accountForTim: TVar[Long]): IO[Unit] =
for {
_ <- IO.sleep(5000.millis)
_ <- stm.commit(accountForTim.modify(_ + 1))
} yield ()
def printBalances(accountForTim: TVar[Long], accountForSteve: TVar[Long]): IO[Unit] =
for {
t <- stm.commit(for {
t <- accountForTim.get
s <- accountForSteve.get
} yield (t, s))
(amountForTim, amountForSteve) = t
_ <- IO(println(s"Tim: $amountForTim"))
_ <- IO(println(s"Steve: $amountForSteve"))
} yield ()
for {
accountForTim <- stm.commit(TVar.of[Long](100))
accountForSteve <- stm.commit(TVar.of[Long](0))
_ <- printBalances(accountForTim, accountForSteve)
_ <- giveTimMoreMoney(accountForTim).start
_ <- transfer(accountForTim, accountForSteve)
_ <- printBalances(accountForTim, accountForSteve)
} yield ()
}
}
```
### Documentation
The documentation is built using [docusaurus](https://docusaurus.io/). You can
generate it via `nix-shell --run "sbt docs/docusaurusCreateSite"` . You can then
view it via `nix-shell --run "cd website && npm start"`.
### Credits
This software was inspired by [Beautiful Concurrency](https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/beautiful.pdf) and the [stm package](http://hackage.haskell.org/package/stm).
Many thanks to [@impurepics](https://twitter.com/impurepics) for the awesome logo!
## Tool Sponsorship
Development of Cats STM is generously supported in part by [YourKit](https://www.yourkit.com) through the use of their excellent Java profiler.