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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