Github user aledsage commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/480#discussion_r101855532
--- Diff:
core/src/main/java/org/apache/brooklyn/util/core/task/InterruptingImmediateSupplier.java
---
@@ -0,0 +1,103 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.brooklyn.util.core.task;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.Semaphore;
+
+import org.apache.brooklyn.util.exceptions.Exceptions;
+import org.apache.brooklyn.util.exceptions.RuntimeInterruptedException;
+import org.apache.brooklyn.util.guava.Maybe;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.Supplier;
+
+/**
+ * Wraps a {@link Supplier} as an {@link ImmediateSupplier} by
interrupting the thread before calling {@link Supplier#get()}.
+ * If the call succeeds, the result is returned.
+ * If the call throws any trace including an {@link InterruptedException}
or {@link RuntimeInterruptedException}
+ * (ie the call failed due to the interruption, typically because it tried
to wait)
+ * then this class concludes that there is no value available immediately
and returns {@link Maybe#absent()}.
+ * If the call throws any other error, that is returned.
+ * The interruption is cleared afterwards (unless the thread was
interrupted when the method was entered).
+ * <p>
+ * Note that some "immediate" methods, such as {@link Semaphore#acquire()}
when a semaphore is available,
+ * will throw if the thread is interrupted. Typically there are
workarounds, for instance:
+ * <code>if (semaphore.tryAcquire()) semaphore.acquire();</code>.
+ */
+@Beta
+public class InterruptingImmediateSupplier<T> implements
ImmediateSupplier<T>, DeferredSupplier<T> {
--- End diff --
I'd add a test specifically for `InterruptingImmediateSupplierTest` (rather
than just testing it indirectly in `EntityConfigTest`). For example:
```
public class InterruptingImmediateSupplierTest {
@Test(expectedExceptions=UnsupportedOperationException.class)
public void testOfInvalidType() throws Exception {
InterruptingImmediateSupplier.of("myval");
}
@Test
public void testRunnable() throws Exception {
assertImmediatelyPresent(Runnables.doNothing(), null);
assertImmediatelyAbsent(new SleepingRunnable());
assertImmediatelyFails(new FailingRunnable(),
MarkerException.class);
}
@Test
public void testCallable() throws Exception {
assertImmediatelyPresent(Callables.returning("myval"), "myval");
assertImmediatelyAbsent(new SleepingCallable());
assertImmediatelyFails(new FailingCallable(),
MarkerException.class);
}
@Test
public void testSupplier() throws Exception {
assertImmediatelyPresent(Suppliers.ofInstance("myval"), "myval");
assertImmediatelyAbsent(new SleepingSupplier());
assertImmediatelyFails(new FailingSupplier(),
MarkerException.class);
}
private void assertImmediatelyPresent(Object orig, Object expected) {
Maybe<Object> result = getImmediately(orig);
assertEquals(result.get(), expected);
assertFalse(Thread.currentThread().isInterrupted());
}
private void assertImmediatelyAbsent(Object orig) {
Maybe<Object> result = getImmediately(orig);
assertTrue(result.isAbsent(), "result="+result);
assertFalse(Thread.currentThread().isInterrupted());
}
private void assertImmediatelyFails(Object orig, Class<? extends
Exception> expected) {
try {
Maybe<Object> result = getImmediately(orig);
Asserts.shouldHaveFailedPreviously("result="+result);
} catch (Exception e) {
Asserts.expectedFailureOfType(e, expected);
}
assertFalse(Thread.currentThread().isInterrupted());
}
private Maybe<Object> getImmediately(Object val) {
InterruptingImmediateSupplier<Object> supplier =
InterruptingImmediateSupplier.of(val);
return supplier.getImmediately();
}
public static class SleepingRunnable implements Runnable {
@Override public void run() {
Time.sleep(Duration.ONE_MINUTE);
}
}
public static class SleepingCallable implements Callable<Void> {
@Override public Void call() {
Time.sleep(Duration.ONE_MINUTE);
return null;
}
}
public static class SleepingSupplier implements Supplier<Void> {
@Override public Void get() {
Time.sleep(Duration.ONE_MINUTE);
return null;
}
}
public static class FailingRunnable implements Runnable {
@Override public void run() {
throw new MarkerException();
}
}
public static class FailingCallable implements Callable<Void> {
@Override public Void call() {
throw new MarkerException();
}
}
public static class FailingSupplier implements Supplier<Void> {
@Override public Void get() {
throw new MarkerException();
}
}
public static class MarkerException extends RuntimeException {
private static final long serialVersionUID = -3395361406478634652L;
}
}
```
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