Github user aledsage commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/480#discussion_r101862310
--- Diff:
core/src/main/java/org/apache/brooklyn/util/core/task/ValueResolver.java ---
@@ -352,33 +357,51 @@ public T get() {
//if the expected type is a closure or map and that's what we
have, we're done (or if it's null);
//but not allowed to return a future or DeferredSupplier as the
resolved value
- if (v==null || (!forceDeep && type.isInstance(v) &&
!Future.class.isInstance(v) && !DeferredSupplier.class.isInstance(v)))
+ if (v==null || (!forceDeep && type.isInstance(v) &&
!Future.class.isInstance(v) && !DeferredSupplier.class.isInstance(v) &&
!TaskFactory.class.isInstance(v)))
return Maybe.of((T) v);
try {
- if (immediately && v instanceof ImmediateSupplier) {
- final ImmediateSupplier<?> supplier =
(ImmediateSupplier<?>) v;
+ if (isEvaluatingImmediately() && v instanceof
ImmediateSupplier) {
+ final ImmediateSupplier<Object> supplier =
(ImmediateSupplier<Object>) v;
try {
- Maybe<?> result = supplier.getImmediately();
+ Maybe<Object> result = exec.getImmediately(supplier);
// Recurse: need to ensure returned value is cast, etc
return (result.isPresent())
? recursive
? new ValueResolver(result.get(), type,
this).getMaybe()
: result
- : Maybe.<T>absent();
+ : result;
} catch (ImmediateSupplier.ImmediateUnsupportedException
e) {
log.debug("Unable to resolve-immediately for
"+description+" ("+v+"); falling back to executing with timeout", e);
}
}
+ // TODO if evaluating immediately should use a new
ExecutionContext.submitImmediate(...)
+ // and sets a timeout but which wraps a task but does not
spawn a new thread
+
+ if ((v instanceof TaskFactory<?>) && !(v instanceof
DeferredSupplier)) {
--- End diff --
I'd add something like the following to `ValueResolverTest`:
```
public void testTaskFactoryGet() {
TaskFactory<TaskAdaptable<String>> taskFactory = new
TaskFactory<TaskAdaptable<String>>() {
@Override public TaskAdaptable<String> newTask() {
return new BasicTask<>(Callables.returning("myval"));
}
};
String result =
Tasks.resolving(taskFactory).as(String.class).context(app).get();
assertEquals(result, "myval");
}
public void testTaskFactoryGetImmediately() {
TaskFactory<TaskAdaptable<String>> taskFactory = new
TaskFactory<TaskAdaptable<String>>() {
@Override public TaskAdaptable<String> newTask() {
return new BasicTask<>(Callables.returning("myval"));
}
};
String result =
Tasks.resolving(taskFactory).as(String.class).context(app).immediately(true).get();
assertEquals(result, "myval");
}
public void testTaskFactoryGetImmediatelyDoesNotBlock() {
final AtomicBoolean executing = new AtomicBoolean();
TaskFactory<TaskAdaptable<String>> taskFactory = new
TaskFactory<TaskAdaptable<String>>() {
@Override public TaskAdaptable<String> newTask() {
return new BasicTask<>(new Callable<String>() {
public String call() {
executing.set(true);
try {
Time.sleep(Duration.ONE_MINUTE);
return "myval";
} finally {
executing.set(false);
}
}});
}
};
Maybe<String> result =
Tasks.resolving(taskFactory).as(String.class).context(app).immediately(true).getMaybe();
assertTrue(result.isAbsent(), "result="+result);
Asserts.succeedsEventually(new Runnable() {
public void run() {
assertFalse(executing.get());
}
});
}
```
However, the last assertion fails - using `immediately()` with
`TaskFactory` is dangerous because the task is left running. It is particularly
dangerous because `immediately()` is most often used when it's being called
regularly (e.g. the rest api wants to list all the config values).
Whose responsibility is it to cancel the task? (It feels like the task
instance is buried inside the `ValueResolver`, so it would be hard for the
caller to get hold of it to cancel it). Should the `ValueResolver` cancel the
task it created, if using `immediately()`?
What are the use-cases for passing a `TaskFactory` into the `ValueResolver`?
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