@SuppressWarnings({"SynchronizationOnLocalVariableOrMethodParameter"})
public Object getInstance(ScopedComponent component) {
Object instance = instances.get(component);
if (instance != EMPTY && instance != null) {
return instance;
}
CountDownLatch latch;
// Avoid race condition where two or more threads attempt to initialize the component instance
// concurrently.
// Pending component instantiations are tracked and threads block on a latch until they are
// complete.
synchronized (component) {
latch = pending.get(component);
if (latch != null) {
try {
// wait on the instantiation
latch.await(5, TimeUnit.MINUTES);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new Fabric3Exception("Error creating instance for: " + component.getUri(), e);
}
// an instance wrapper is now available as the instantiation has completed
return instances.get(component);
} else {
latch = new CountDownLatch(1);
pending.put(component, latch);
}
}
try {
instance = component.createInstance();
// some component instances such as system singletons may already be started
// if (!component.isInstanceStarted()) {
component.startInstance(instance);
List<Pair> queue;
URI uri = component.getContributionUri();
synchronized (destroyQueues) {
queue = destroyQueues.get(uri);
if (queue == null) {
// The context has not been initialized. This can happen if two deployable composites are
// deployed simultaneously and a
// component in the first composite to be deployed references a component in the second
// composite. In this case,
// create the destroy queue prior to the context being started.
queue = new ArrayList<>();
destroyQueues.put(uri, queue);
}
}
queue.add(new Pair(component, instance));
// }
instances.put(component, instance);
latch.countDown();
return instance;
} finally {
pending.remove(component);
}
}
