TxnExecutor

Executes block one or more times until an atomic execution is achieved, buffering and/or locking writes so they are not visible until success.

Atomically compares and sets two Refs, probably more efficiently then the corresponding transaction. Equivalent to

atomic { implicit t =>
a() == a0 && b() == b0 && { a() = a1 ; b() = b1 ; true }
}

Atomically compares and sets two Refs using identity comparison, probably more efficiently then the corresponding transaction. Equivalent to

atomic { implicit t =>
val f = (a() eq a0) && (b() eq b0)
if (f && (a0 ne a1))
  a() = a1
if (f && (b0 ne b1))
  b() = b1
f
}

Returns true if x should be treated as a transfer of control, rather than an error. Atomic blocks that end with an uncaught control flow exception are committed, while atomic blocks that end with an uncaught error exception are rolled back.

All implementations of this method must return true for instances that implement scala.util.control.ControlThrowable.

Atomically executes a transaction that is composed from blocks by joining with a left-biased orAtomic operator. The following two examples are equivalent. Using orAtomic:

atomic { implicit t =>
  // body A
} orAtomic { implicit t =>
  // body B
} ...

Using oneOf:

atomic.oneOf( { implicit t: InTxn =>
  // body A
}, { implicit t: InTxn =>
  // body B
} )

The first block will be attempted in an optimistic transaction until it either succeeds, fails with no retry possible (in which case the causing exception will be rethrown), or performs a call to retry. If a retry is requested, then the next block will be attempted in the same fashion. If all blocks are explicitly retried then execution resumes at the first block, but only after another context has changed some value read by one of the attempts.

The left-biasing of the orAtomic composition guarantees that if the first block does not call retry, no other blocks will be executed.

(rare) Associates an alternative atomic block with the current thread. The next call to apply will consider block to be an alternative. Multiple alternatives may be associated before calling apply. Returns true if this is the first pushed alternative, false otherwise. This method is not usually called directly. Alternative atomic blocks are only attempted if the previous alternatives call retry.

Note that it is not required that pushAlternative be called on the same instance of TxnExecutor as apply, just that they have been derived from the same original executor.

Returns Some(t) if t is the retry timeout in nanoseconds used by this TxnExecutor, or None otherwise. If the retry timeout is Some(t) and an atomic block executed by the returned executor blocks with retry or retryFor for more than t nanoseconds the retry will be cancelled with an InterruptedException.

The retry timeout has essentially the same effect as replacing calls to retry with { retryFor(timeout, NANOS) ; throw new InterruptedException }. Alternately, retryFor(timeout) has roughly the same effect as

try {
  atomic.withRetryTimeout(timeout) { implicit txn => retry }
} catch {
  case _: InterruptedException =>
}

Performs a computation in a transaction and returns the result, but always rolls back the transaction. No writes performed by block will be committed or exposed to other threads. This may be useful for heuristic decisions or for debugging, as for the various dbgStr implementations.

The caller is responsible for correctness: It is a code smell if Z is a type that is constructed from Ref, TMap, TSet, .....

If this method is executed inside an outer transaction that has status Txn.RolledBack then block can't complete. The default behavior (if outerFailure is null) in that case is to immediately roll back the outer transaction. If a non-null outerFailure handler has been provided, however, it allow this method to return. This is useful when the unrecorded transaction is being used for debugging or logging.

atomic.unrecorded { implicit txn => code } is roughly equivalent to the following, except that the rollback cause used will be Txn.UnrecordedTxnCause:

case class Tunnel(z: Z) extends Exception {}
try {
  atomic.withControlFlowRecognizer({
    case Tunnel(_) => false
  }) { implicit txn =>
    throw Tunnel(code)
  }
} catch {
  case Tunnel(z) => z
}

Returns a TxnExecutor e that is identical to this one, except that e.isControlFlow(x) will return pf(x) if pf.isDefined(x). For exceptions for which pf is not defined the decision will be deferred to the previous implementation.

This function may be combined with TxnExecutor.transformDefault to add system-wide recognition of a control-transfer exception that does not extend scala.util.control.ControlThrowable. For example, to modify the default behavior of all TxnExecutor.isControlFlow calls to accept DSLNonLocalControlTransferException:

TxnExecutor.transformDefault { e =>
e.withControlFlowRecognizer {
  case _: DSLNonLocalControlTransferException => true
}
}

Returns a TxnExecutor e that is identical to this one, except that e.postDecisionFailureHandler will return handler. This function may be called from inside a function passed to TxnExecutor.transformDefault to change the system-wide post-decision failure handler.

Returns a TxnExecutor that is identical to this one except that it has the specified retry timeout. The default time unit is milliseconds. If the retry timeout expires the retry will be cancelled with an InterruptedException.