Prototype Safe Semaphore #1523

adamgfraser · 2019-08-29T23:57:32Z

Resolves #1511. We actually didn't keep track of the number of permits before because it didn't matter as long as we started out with a certain number and didn't leak them. I added a value to record the number of permits. Change required was very minimal.

Only other thing to think about is in the case of TRef I had to abandon it extending AnyVal because now it has two parameters. We could try go put the value in the TRef instead or put them both in a case class but I think we lose as much as we gain that way.

…, &> (#1510) * Add ZStrem#zip left and right operators and alias for all zip operators * formatted code to make scalafmtCheck pass. * change for <*> variants with flatmap and <&> with zipWith. * adding crossWith and cross functions to ZStream. * merge conflict change. * formatted naming conventions.

adamgfraser · 2019-09-21T09:21:41Z

This could use some feedback if we want to do anything on it for the 1.0 release.

regiskuckaertz · 2019-09-21T09:47:44Z

core-tests/jvm/src/test/scala/zio/SemaphoreSpec.scala

      semaphore <- Semaphore.make(n)
-      available <- IO.foreach((0L until n).toList)(_ => semaphore.acquire) *> semaphore.available
-    } yield available must_=== 0)
+      available <- IO.foreach((0L until n).toList)(_ => semaphore.withPermit(semaphore.available))


Makes me want to add a semaphore.withAllPermits

... nothing to do with the test though, just thought that one might want a monopoly over all permits.

Yes, if we went with this approach we could definitely maintain a val with the total number of permits and expose a withAllPermits method.

regiskuckaertz · 2019-09-21T09:54:53Z

docs/datatypes/semaphore.md

 ---

-A `Semaphore` datatype which allows synchronization between fibers with `acquire` and `release` operations.
+A `Semaphore` datatype which allows synchronization between fibers with the `withPermit` operation, which safely acquires and releases a permit.


Note that it is still possible to trick the system by asking for a negative number of permits.

Wouldn't assertNonNegative cause the fiber to die at that point?

Yes, on release, which seems wrong 🤔 It's like catching a bad guy when it's too late 😆

I see. Yes we could definitely fix that.

regiskuckaertz · 2019-09-21T09:55:37Z

You have my vote, I'd just like to clarify the behaviour when passing a negative number (right now prepare deals with the case where n == 0)

adamgfraser · 2019-09-21T10:33:00Z

@regiskuckaertz I added a fix for this.

core-tests/jvm/src/test/scala/zio/RTSSpec.scala

regiskuckaertz

I love it. I think I would move the assertNonNegative out of prepare and release now, as ostensibly the latter would never get evaluated anyway.

adamgfraser · 2019-09-21T11:07:53Z

@regiskuckaertz Sorry, don't we need it in prepare? Agree we can move it out of releaseN.

regiskuckaertz

Yes of course 🤦‍♂️ This is great!

adamgfraser · 2019-09-23T19:49:57Z

@jdegoes When you have the chance could I get some feedback on whether you want to move forward with this? If so I think the next steps would be adding a couple of convenience methods on Semaphore (maxPermits and withAllPermits) and deciding how, if at all, we want to change TSemaphore based on this.

jdegoes · 2019-10-28T09:07:22Z

core/shared/src/main/scala/zio/Semaphore.scala

-   * If the specified number of permits are not available, the fiber invoking
-   * this method will be suspended until the permits are available.
-   *
-   * Ported from @mpilquist work in Cats Effect (https://github.com/typelevel/cats-effect/pull/403)


We should preserve this attribution comment in any case.

jdegoes · 2019-10-28T09:07:48Z

core/shared/src/main/scala/zio/Semaphore.scala

-  /**
-   * Releases a single permit.
-   */
-  final def release: UIO[Unit] = releaseN(1)


Because code uses these functions, we should at least deprecate them until 1.0.

adamgfraser · 2019-10-28T15:14:18Z

I incorporated your comments. The changes are pretty small at this point, just deprecating the methods on Semaphore and updating the tests to note use those methods, but good to deprecate them now if we are going to take them out. This is ready for another review.

adamgfraser · 2019-11-07T16:15:12Z

@jdegoes Sorry could you approve one more time? Had to resolve a merge conflict.

adamgfraser · 2019-11-07T16:38:54Z

@regiskuckaertz Thanks!

* implement permits * make TRef state private * prototype safe semaphore * implement permits * make TRef state private * zio#1219 - add doUntilEquals and doWhileEquals methods (zio#1634) * Update zio-interop-reactivestreams to 1.0.3.1-RC1 (zio#1665) * Add ZStream#cross, crossWith, <*>, <*, *>, <&>, zipLeft, zipRight, <&, &> (zio#1510) * Add ZStrem#zip left and right operators and alias for all zip operators * formatted code to make scalafmtCheck pass. * change for <*> variants with flatmap and <&> with zipWith. * adding crossWith and cross functions to ZStream. * merge conflict change. * formatted naming conventions. * Update the encoding of ZSink (zio#1560) * prototype safe semaphore * cleanup * uodate documentation * address review comments * cleanup * add back and deprecate methods * cleanup * make method private

adamgfraser added 2 commits August 29, 2019 19:45

implement permits

12654df

make TRef state private

fb0cdaa

adamgfraser changed the title ~~Implement Semaphore#Permits and TSemaphore#Permits~~ Implement Semaphore#permits and TSemaphore#permits Aug 30, 2019

adamgfraser and others added 11 commits September 13, 2019 20:23

prototype safe semaphore

53da6cd

resolve merge conflicts

e83adb4

implement permits

65dfdc0

make TRef state private

3492a20

#1219 - add doUntilEquals and doWhileEquals methods (#1634)

6d19e4f

Update zio-interop-reactivestreams to 1.0.3.1-RC1 (#1665)

f27ec9e

Update the encoding of ZSink (#1560)

d27a21d

prototype safe semaphore

2f011b2

Merge branch '1511' of https://github.com/adamgfraser/zio into 1511

ff87a26

cleanup

7fec2a2

adamgfraser changed the title ~~Implement Semaphore#permits and TSemaphore#permits~~ Prototype Safe Semaphore Sep 14, 2019

uodate documentation

5800058

adamgfraser mentioned this pull request Sep 14, 2019

Add Semaphore#permits #1511

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regiskuckaertz reviewed Sep 21, 2019

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address review comments

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core-tests/jvm/src/test/scala/zio/RTSSpec.scala Outdated Show resolved Hide resolved

regiskuckaertz previously approved these changes Sep 21, 2019

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cleanup

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adamgfraser dismissed regiskuckaertz’s stale review via 5d163e2 September 21, 2019 11:20

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merge upstream changes

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adamgfraser dismissed regiskuckaertz’s stale review via d71f997 September 23, 2019 19:38

adamgfraser requested a review from jdegoes September 23, 2019 19:50

jdegoes reviewed Oct 28, 2019

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adamgfraser added 4 commits October 28, 2019 10:41

merge upstream changes

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add back and deprecate methods

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cleanup

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make method private

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jdegoes previously approved these changes Nov 2, 2019

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merge upstream changes

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adamgfraser dismissed jdegoes’s stale review via a9a8c5f November 7, 2019 10:52

regiskuckaertz approved these changes Nov 7, 2019

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adamgfraser merged commit 0c32182 into zio:master Nov 7, 2019

adamgfraser deleted the 1511 branch November 7, 2019 16:38

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Prototype Safe Semaphore #1523

Prototype Safe Semaphore #1523

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adamgfraser commented Aug 29, 2019

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