Acquires a single permit in transactional context.
Acquires the specified number of permits in a transactional context.
Returns the number of available permits in a transactional context.
Releases a single permit in a transactional context.
Releases the specified number of permits in a transactional context
Executes the specified effect, acquiring a permit immediately before the effect begins execution and releasing it immediately after the effect completes execution, whether by success, failure, or interruption.
Returns a scoped effect that describes acquiring a permit as the acquire
action and releasing it as the release
action.
Executes the specified effect, acquiring the specified number of permits immediately before the effect begins execution and releasing them immediately after the effect completes execution, whether by success, failure, or interruption.
Returns a scoped effect that describes acquiring the specified number of permits and releasing them when the scope is closed.
A
TSemaphore
is a semaphore that can be composed transactionally. Because of the extremely high performance of ZIO's implementation of software transactional memoryTSemaphore
can support both controlling access to some resource on a standalone basis as well as composing with other STM data structures to solve more advanced concurrency problems.For basic use cases, the most idiomatic way to work with a semaphore is to use the
withPermit
operator, which acquires a permit before executing someZIO
effect and release the permit immediately afterward. The permit is guaranteed to be released immediately after the effect completes execution, whether by success, failure, or interruption. Attempting to acquire a permit when a sufficient number of permits are not available will semantically block until permits become available without blocking any underlying operating system threads. If you want to acquire more than one permit at a time you can usewithPermits
, which allows specifying a number of permits to acquire. You can also usewithPermitScoped
orwithPermitsScoped
to acquire and release permits within the context of a scoped effect for composing with other resources.For more advanced concurrency problems you can use the
acquire
andrelease
operators directly, or their variantsacquireN
andreleaseN
, all of which return STM transactions. Thus, they can be composed to form larger STM transactions, for example acquiring permits from two different semaphores transactionally and later releasing them transactionally to safely synchronize on access to two different mutable variables.