STM[E, A]
represents an effect that can be performed transactionally,
resulting in a failure E
or a value A
.
def transfer(receiver: TRef[Int],
sender: TRef[Int], much: Int): UIO[Int] =
STM.atomically {
for {
balance <- sender.get
_ <- STM.check(balance >= much)
_ <- receiver.update(_ + much)
_ <- sender.update(_ - much)
newAmnt <- receiver.get
} yield newAmnt
}
val action: UIO[Int] =
for {
t <- STM.atomically(TRef.make(0).zip(TRef.make(20000)))
(receiver, sender) = t
balance <- transfer(receiver, sender, 1000)
} yield balance
Software Transactional Memory is a technique which allows composition of arbitrary atomic operations. It is the software analog of transactions in database systems.
The API is lifted directly from the Haskell package Control.Concurrent.STM although the implementation does not resemble the Haskell one at all. http://hackage.haskell.org/package/stm-2.5.0.0/docs/Control-Concurrent-STM.html
STM in Haskell was introduced in: Composable memory transactions, by Tim Harris, Simon Marlow, Simon Peyton Jones, and Maurice Herlihy, in ACM Conference on Principles and Practice of Parallel Programming 2005. https://www.microsoft.com/en-us/research/publication/composable-memory-transactions/
See also: Lock Free Data Structures using STMs in Haskell, by Anthony Discolo, Tim Harris, Simon Marlow, Simon Peyton Jones, Satnam Singh) FLOPS 2006: Eighth International Symposium on Functional and Logic Programming, Fuji Susono, JAPAN, April 2006 https://www.microsoft.com/en-us/research/publication/lock-free-data-structures-using-stms-in-haskell/
- Companion:
- object
Value members
Concrete methods
Splits the environment, providing the first part to this effect and the second part to that effect.
Splits the environment, providing the first part to this effect and the second part to that effect.
Sequentially zips this value with the specified one, discarding the first element of the tuple.
Sequentially zips this value with the specified one, discarding the first element of the tuple.
Depending on provided environment, returns either this one or the other
effect lifted in Left
or Right
, respectively.
Depending on provided environment, returns either this one or the other
effect lifted in Left
or Right
, respectively.
Sequentially zips this value with the specified one, discarding the second element of the tuple.
Sequentially zips this value with the specified one, discarding the second element of the tuple.
Sequentially zips this value with the specified one.
Sequentially zips this value with the specified one.
Tries this effect first, and if it fails or retries, tries the other effect.
Tries this effect first, and if it fails or retries, tries the other effect.
Tries this effect first, and if it enters retry, then it tries the other effect. This is an equivalent of haskell's orElse.
Tries this effect first, and if it enters retry, then it tries the other effect. This is an equivalent of haskell's orElse.
Feeds the value produced by this effect to the specified function, and then runs the returned effect as well to produce its results.
Feeds the value produced by this effect to the specified function, and then runs the returned effect as well to produce its results.
Returns an effect that submerges the error case of an Either
into the
STM
. The inverse operation of STM.either
.
Returns an effect that submerges the error case of an Either
into the
STM
. The inverse operation of STM.either
.
Maps the success value of this effect to the specified constant value.
Maps the success value of this effect to the specified constant value.
Maps the success value of this effect to an optional value.
Maps the success value of this effect to an optional value.
Maps the error value of this effect to an optional value.
Maps the error value of this effect to an optional value.
Recovers from some or all of the error cases.
Recovers from some or all of the error cases.
Simultaneously filters and maps the value produced by this effect.
Simultaneously filters and maps the value produced by this effect.
Simultaneously filters and flatMaps the value produced by this effect. Continues on the effect returned from pf.
Simultaneously filters and flatMaps the value produced by this effect. Continues on the effect returned from pf.
Commits this transaction atomically, regardless of whether the transaction is a success or a failure.
Commits this transaction atomically, regardless of whether the transaction is a success or a failure.
Executes the specified finalization transaction whether or not this effect succeeds. Note that as with all STM transactions, if the full transaction fails, everything will be rolled back.
Executes the specified finalization transaction whether or not this effect succeeds. Note that as with all STM transactions, if the full transaction fails, everything will be rolled back.
Returns an effect that ignores errors and runs repeatedly until it eventually succeeds.
Returns an effect that ignores errors and runs repeatedly until it eventually succeeds.
Dies with specified Throwable
if the predicate fails.
Dies with specified Throwable
if the predicate fails.
Dies with a java.lang.RuntimeException having the specified text message if the predicate fails.
Dies with a java.lang.RuntimeException having the specified text message if the predicate fails.
Applies f
if the predicate fails.
Applies f
if the predicate fails.
Supplies zstm
if the predicate fails.
Supplies zstm
if the predicate fails.
Feeds the value produced by this effect to the specified function, and then runs the returned effect as well to produce its results.
Feeds the value produced by this effect to the specified function, and then runs the returned effect as well to produce its results.
Creates a composite effect that represents this effect followed by another one that may depend on the error produced by this one.
Creates a composite effect that represents this effect followed by another one that may depend on the error produced by this one.
Unwraps the optional error, defaulting to the provided value.
Unwraps the optional error, defaulting to the provided value.
Flips the success and failure channels of this transactional effect. This allows you to use all methods on the error channel, possibly before flipping back.
Flips the success and failure channels of this transactional effect. This allows you to use all methods on the error channel, possibly before flipping back.
Swaps the error/value parameters, applies the function f
and flips the
parameters back
Swaps the error/value parameters, applies the function f
and flips the
parameters back
Folds over the STM
effect, handling both failure and success, but not
retry.
Folds over the STM
effect, handling both failure and success, but not
retry.
Effectfully folds over the STM
effect, handling both failure and success.
Effectfully folds over the STM
effect, handling both failure and success.
Unwraps the optional success of this effect, but can fail with None value.
Unwraps the optional success of this effect, but can fail with None value.
Returns a successful effect with the head of the list if the list is
non-empty or fails with the error None
if the list is empty.
Returns a successful effect with the head of the list if the list is
non-empty or fails with the error None
if the list is empty.
Returns a new effect that ignores the success or failure of this effect.
Returns a new effect that ignores the success or failure of this effect.
Returns whether this transactional effect is a failure.
Returns whether this transactional effect is a failure.
Returns whether this transactional effect is a success.
Returns whether this transactional effect is a success.
Returns a successful effect if the value is Left
, or fails with the error
None
.
Returns a successful effect if the value is Left
, or fails with the error
None
.
Returns a successful effect if the value is Left
, or fails with the error
e.
Returns a successful effect if the value is Left
, or fails with the error
e.
Returns a successful effect if the value is Left
, or fails with a
java.util.NoSuchElementException.
Returns a successful effect if the value is Left
, or fails with a
java.util.NoSuchElementException.
Returns an STM
effect whose failure and success channels have been mapped
by the specified pair of functions, f
and g
.
Returns an STM
effect whose failure and success channels have been mapped
by the specified pair of functions, f
and g
.
Maps the value produced by the effect with the specified function that may throw exceptions but is otherwise pure, translating any thrown exceptions into typed failed effects.
Maps the value produced by the effect with the specified function that may throw exceptions but is otherwise pure, translating any thrown exceptions into typed failed effects.
Returns a new effect where the error channel has been merged into the success channel to their common combined type.
Returns a new effect where the error channel has been merged into the success channel to their common combined type.
Requires the option produced by this value to be None
.
Requires the option produced by this value to be None
.
Propagates the success value to the first element of a tuple, but passes
the effect input R
along unmodified as the second element of the tuple.
Propagates the success value to the first element of a tuple, but passes
the effect input R
along unmodified as the second element of the tuple.
Returns this effect if environment is on the left, otherwise returns whatever is on the right unmodified. Note that the result is lifted in either.
Returns this effect if environment is on the left, otherwise returns whatever is on the right unmodified. Note that the result is lifted in either.
Returns this effect if environment is on the right, otherwise returns whatever is on the left unmodified. Note that the result is lifted in either.
Returns this effect if environment is on the right, otherwise returns whatever is on the left unmodified. Note that the result is lifted in either.
Propagates the success value to the second element of a tuple, but passes
the effect input R
along unmodified as the first element of the tuple.
Propagates the success value to the second element of a tuple, but passes
the effect input R
along unmodified as the first element of the tuple.
Converts an option on errors into an option on values.
Converts an option on errors into an option on values.
Translates STM
effect failure into death of the fiber, making all
failures unchecked and not a part of the type of the effect.
Translates STM
effect failure into death of the fiber, making all
failures unchecked and not a part of the type of the effect.
Keeps none of the errors, and terminates the fiber running the STM
effect
with them, using the specified function to convert the E
into a
Throwable
.
Keeps none of the errors, and terminates the fiber running the STM
effect
with them, using the specified function to convert the E
into a
Throwable
.
Returns a transactional effect that will produce the value of this effect in left side, unless it fails or retries, in which case, it will produce the value of the specified effect in right side.
Returns a transactional effect that will produce the value of this effect in left side, unless it fails or retries, in which case, it will produce the value of the specified effect in right side.
Tries this effect first, and if it fails or retries, fails with the specified error.
Tries this effect first, and if it fails or retries, fails with the specified error.
Returns an effect that will produce the value of this effect, unless it
fails with the None
value, in which case it will produce the value of the
specified effect.
Returns an effect that will produce the value of this effect, unless it
fails with the None
value, in which case it will produce the value of the
specified effect.
Tries this effect first, and if it fails or retries, succeeds with the specified value.
Tries this effect first, and if it fails or retries, succeeds with the specified value.
Provides the transaction its required environment, which eliminates its
dependency on R
.
Provides the transaction its required environment, which eliminates its
dependency on R
.
Provides some of the environment required to run this effect, leaving the
remainder R0
.
Provides some of the environment required to run this effect, leaving the
remainder R0
.
Keeps some of the errors, and terminates the fiber with the rest.
Keeps some of the errors, and terminates the fiber with the rest.
Keeps some of the errors, and terminates the fiber with the rest, using the
specified function to convert the E
into a Throwable
.
Keeps some of the errors, and terminates the fiber with the rest, using the
specified function to convert the E
into a Throwable
.
Fail with the returned value if the PartialFunction
matches, otherwise
continue with our held value.
Fail with the returned value if the PartialFunction
matches, otherwise
continue with our held value.
Continue with the returned computation if the PartialFunction
matches,
translating the successful match into a failure, otherwise continue with
our held value.
Continue with the returned computation if the PartialFunction
matches,
translating the successful match into a failure, otherwise continue with
our held value.
Repeats this STM
effect until its result satisfies the specified
predicate. '''WARNING''': repeatUntil
uses a busy loop to repeat the
effect and will consume a thread until it completes (it cannot yield). This
is because STM describes a single atomic transaction which must either
complete, retry or fail a transaction before yielding back to the ZIO
Runtime.
Repeats this STM
effect until its result satisfies the specified
predicate. '''WARNING''': repeatUntil
uses a busy loop to repeat the
effect and will consume a thread until it completes (it cannot yield). This
is because STM describes a single atomic transaction which must either
complete, retry or fail a transaction before yielding back to the ZIO
Runtime.
- Use retryUntil instead if you don't need to maintain transaction state for repeats.
- Ensure repeating the STM effect will eventually satisfy the predicate.
- Consider using the Blocking thread pool for execution of the transaction.
Repeats this STM
effect while its result satisfies the specified
predicate. '''WARNING''': repeatWhile
uses a busy loop to repeat the
effect and will consume a thread until it completes (it cannot yield). This
is because STM describes a single atomic transaction which must either
complete, retry or fail a transaction before yielding back to the ZIO
Runtime.
Repeats this STM
effect while its result satisfies the specified
predicate. '''WARNING''': repeatWhile
uses a busy loop to repeat the
effect and will consume a thread until it completes (it cannot yield). This
is because STM describes a single atomic transaction which must either
complete, retry or fail a transaction before yielding back to the ZIO
Runtime.
- Use retryWhile instead if you don't need to maintain transaction state for repeats.
- Ensure repeating the STM effect will eventually not satisfy the predicate.
- Consider using the Blocking thread pool for execution of the transaction.
Filters the value produced by this effect, retrying the transaction until the predicate returns true for the value.
Filters the value produced by this effect, retrying the transaction until the predicate returns true for the value.
Filters the value produced by this effect, retrying the transaction while the predicate returns true for the value.
Filters the value produced by this effect, retrying the transaction while the predicate returns true for the value.
Returns a successful effect if the value is Right
, or fails with the
error None
.
Returns a successful effect if the value is Right
, or fails with the
error None
.
Returns a successful effect if the value is Right
, or fails with the
given error 'e'.
Returns a successful effect if the value is Right
, or fails with the
given error 'e'.
Returns a successful effect if the value is Right
, or fails with a
java.util.NoSuchElementException.
Returns a successful effect if the value is Right
, or fails with a
java.util.NoSuchElementException.
Converts an option on values into an option on errors.
Converts an option on values into an option on errors.
Extracts the optional value, or returns the given 'default'.
Extracts the optional value, or returns the given 'default'.
Extracts the optional value, or executes the effect 'default'.
Extracts the optional value, or executes the effect 'default'.
Extracts the optional value, or fails with the given error 'e'.
Extracts the optional value, or fails with the given error 'e'.
Extracts the optional value, or fails with a java.util.NoSuchElementException
Extracts the optional value, or fails with a java.util.NoSuchElementException
Summarizes a STM
effect by computing a provided value before and after
execution, and then combining the values to produce a summary, together
with the result of execution.
Summarizes a STM
effect by computing a provided value before and after
execution, and then combining the values to produce a summary, together
with the result of execution.
The moral equivalent of if (!p) exp
when p
has side-effects
The moral equivalent of if (!p) exp
when p
has side-effects
Updates a service in the environment of this effect.
Updates a service in the environment of this effect.
The moral equivalent of if (p) exp
when p
has side-effects
The moral equivalent of if (p) exp
when p
has side-effects
Deprecated methods
Returns an STM
effect whose failure and success channels have been mapped
by the specified pair of functions, f
and g
.
Returns an STM
effect whose failure and success channels have been mapped
by the specified pair of functions, f
and g
.
- Deprecated
Repeats this effect forever (until the first error). '''WARNING''':
forever
uses a busy loop to repeat the effect and will consume a thread
until it fails. This is because STM describes a single atomic transaction,
and so must either complete, retry or fail a transaction before yielding
back to the ZIO Runtime.
Repeats this effect forever (until the first error). '''WARNING''':
forever
uses a busy loop to repeat the effect and will consume a thread
until it fails. This is because STM describes a single atomic transaction,
and so must either complete, retry or fail a transaction before yielding
back to the ZIO Runtime.
- Ensure repeating the STM effect will eventually fail.
- Consider using the Blocking thread pool for execution of the transaction.
- Deprecated