@tysonnorris
- for the `if delta < 0 =>`, I think the `s.setMaxPermits(5) // reduce max
permits` match the case
- for the concurrent situations, I added below tests
```
it should "set the max allowed permits while call release concurrently" in {
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
s.tryAcquire(32) // 0 permits left
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(16) // force acquire 16 permits
else
s.release()
}
s.availablePermits shouldBe 47 // 0 - 16 + 63
}
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
s.tryAcquire(32) // 0 permits left
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(64) // release 32 permits
else
s.release()
}
s.availablePermits shouldBe 95 // 0 + 32 + 63
}
}
it should "set the max allowed permits while call forceAcquire concurrently"
in {
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(16) // force acquire 16 permits
else
s.forceAcquire()
}
s.availablePermits shouldBe -47 // 32 - 16 - 63
}
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(64) // release 32 permits
else
s.forceAcquire()
}
s.availablePermits shouldBe 1 // 32 + 32 - 63
}
}
it should "set the max allowed permits while call tryAcquire concurrently" in
{
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(16) // force acquire 16 permits
else
s.tryAcquire()
}
s.availablePermits shouldBe ??? // not sure how many tryAcquire succeed
}
(0 until 100).foreach { _ =>
val s = new ForcibleSemaphore(32)
(0 until 64).par.map{ i =>
if ( i == 16)
s.setMaxPermits(64) // release 32 permits
else
s.tryAcquire()
}
s.availablePermits shouldBe ??? // not sure how many tryAcquire succeed
}
}
```
the first two tests will succeed while the last one will not, I believe the
reason is that the `nonFairTryAcquireShared` will not change the state while
`available - acquires < 0`, so we can not make sure a `tryAcquire` is success
or not while `setMaxPermits` is in flight, any advice?
```
@tailrec
final def nonFairTryAcquireShared(acquires: Int): Int = {
val available = getState
val remaining = available - acquires
if (remaining < 0 || compareAndSetState(available, remaining)) {
remaining
} else {
nonFairTryAcquireShared(acquires)
}
}
```
[ Full content available at:
https://github.com/apache/incubator-openwhisk/pull/3656 ]
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