RunMonitor
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A RunMonitor allows the registration of ICancellable
objects, which are cancelled upon cancellation of this monitor. A RunMonitor is associated with every RunContext and IFuture, meaning that executing code can always query its current cancellation status via RunMonitor.CURRENT.get().isCancelled()
.
A RunMonitor
itself is also of the type ICancellable
, meaning that it can be registered within another monitor as well. That way, a monitor hierarchy can be created with support of nested cancellation. That is exactly what is done when creating a copy of the current calling context, namely that the new monitor is registered as ICancellable
within the monitor of the current calling context. Cancellation only works top-down, and not bottom up, meaning that a parent monitor is not cancelled once a child monitor is cancelled.
When registering a ICancellable
and this monitor is already cancelled, the ICancellable
is cancelled immediately.
Furthermore, a job’s Future is linked with the job’s RunMonitor
, meaning that cancellation requests targeted to the Future
are also propagated to the RunMonitor
, and vice versa.
The following Figure 1 illustrates the RunMonitor
and its associations.