Github user aledsage commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/480#discussion_r103448474
--- Diff:
core/src/main/java/org/apache/brooklyn/util/core/task/BasicExecutionContext.java
---
@@ -96,7 +98,50 @@ public ExecutionManager getExecutionManager() {
/** returns tasks started by this context (or tasks which have all the
tags on this object) */
@Override
public Set<Task<?>> getTasks() { return
executionManager.getTasksWithAllTags(tags); }
-
+
+ /** performs execution without spawning a new task thread, though it
does temporarily set a fake task for the purpose of getting context;
+ * currently supports suppliers or callables */
+ @SuppressWarnings("unchecked")
+ @Override
+ public <T> Maybe<T> getImmediately(Object callableOrSupplier) {
+ BasicTask<?> fakeTaskForContext;
+ if (callableOrSupplier instanceof BasicTask) {
+ fakeTaskForContext = (BasicTask<?>)callableOrSupplier;
+ if (fakeTaskForContext.isQueuedOrSubmitted()) {
+ if (fakeTaskForContext.isDone()) {
+ return Maybe.of((T)fakeTaskForContext.getUnchecked());
+ } else {
+ throw new ImmediateUnsupportedException("Task is in
progress and incomplete: "+fakeTaskForContext);
+ }
+ }
+ callableOrSupplier = fakeTaskForContext.getJob();
--- End diff --
Very clever, getting the underlying `Callable` to execute from the job!
However, I wonder if this just reduces the chance of leaving tasks behind
(rather than preventing it).
The test below fails when added to `ValueResolverTest` (when also including
the change to `ValueResolver.getMaybeInternal()` to set
`allowImmediateExecution = true` so that this code path is taken).
```
public void testTaskGetImmediatelyDoesNotBlockWithNestedTasks() {
final AtomicInteger executingCount = new AtomicInteger();
final SequentialTask<?> outerTask = new
SequentialTask<>(ImmutableList.of(new Callable<String>() {
public String call() {
executingCount.incrementAndGet();
try {
Time.sleep(Duration.ONE_MINUTE);
return "myval";
} finally {
executingCount.decrementAndGet();
}
}}));
for (int i = 0; i < 3; i++) {
Maybe<String> result =
Tasks.resolving(outerTask).as(String.class).context(app).immediately(true).getMaybe();
Asserts.assertTrue(result.isAbsent(), "result="+result);
}
Asserts.assertFalse(outerTask.isSubmitted());
// the call below default times out after 30s while the task above
is still running
Asserts.succeedsEventually(new Runnable() {
public void run() {
Asserts.assertEquals(executingCount.get(), 0);
}
});
}
```
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