/**
* Updates the state with the given service transition.
*
* <p>This method performs the main logic of ServiceManager in the following steps.
*
* <ol>
* <li>Update the {@link #servicesByState()}
* <li>Update the {@link #startupTimers}
* <li>Based on the new state queue listeners to run
* <li>Run the listeners (outside of the lock)
* </ol>
*/
void transitionService(final Service service, State from, State to) {
checkNotNull(service);
checkArgument(from != to);
monitor.enter();
try {
transitioned = true;
if (!ready) {
return;
}
// Update state.
checkState(
servicesByState.remove(from, service),
"Service %s not at the expected location in the state map %s",
service,
from);
checkState(
servicesByState.put(to, service),
"Service %s in the state map unexpectedly at %s",
service,
to);
// Update the timer
Stopwatch stopwatch = startupTimers.get(service);
if (stopwatch == null) {
// This means the service was started by some means other than ServiceManager.startAsync
stopwatch = Stopwatch.createStarted();
startupTimers.put(service, stopwatch);
}
if (to.compareTo(RUNNING) >= 0 && stopwatch.isRunning()) {
// N.B. if we miss the STARTING event then we may never record a startup time.
stopwatch.stop();
if (!(service instanceof NoOpService)) {
logger.log(Level.FINE, "Started {0} in {1}.", new Object[] {service, stopwatch});
}
}
// Queue our listeners
// Did a service fail?
if (to == FAILED) {
fireFailedListeners(service);
}
if (states.count(RUNNING) == numberOfServices) {
// This means that the manager is currently healthy. N.B. If other threads call isHealthy
// they are not guaranteed to get 'true', because any service could fail right now.
fireHealthyListeners();
} else if (states.count(TERMINATED) + states.count(FAILED) == numberOfServices) {
fireStoppedListeners();
}
} finally {
monitor.leave();
// Run our executors outside of the lock
executeListeners();
}
}
ImmutableMultimap<State, Service> servicesByState() {
ImmutableSetMultimap.Builder<State, Service> builder = ImmutableSetMultimap.builder();
monitor.enter();
try {
for (Entry<State, Service> entry : servicesByState.entries()) {
if (!(entry.getValue() instanceof NoOpService)) {
builder.put(entry.getKey(), entry.getValue());
}
}
} finally {
monitor.leave();
}
return builder.build();
}
/**
* It is implicitly assumed that all the services are NEW and that they will all remain NEW
* until all the Listeners are installed and {@link #markReady()} is called. It is our caller's
* responsibility to only call {@link #markReady()} if all services were new at the time this
* method was called and when all the listeners were installed.
*/
ServiceManagerState(ImmutableCollection<Service> services) {
this.numberOfServices = services.size();
servicesByState.putAll(NEW, services);
}
/**
* An encapsulation of all the mutable state of the {@link ServiceManager} that needs to be
* accessed by instances of {@link ServiceListener}.
*/
private static final class ServiceManagerState {
final Monitor monitor = new Monitor();
@GuardedBy("monitor")
final SetMultimap<State, Service> servicesByState =
Multimaps.newSetMultimap(
new EnumMap<State, Collection<Service>>(State.class),
new Supplier<Set<Service>>() {
@Override
public Set<Service> get() {
return Sets.newLinkedHashSet();
}
});
@GuardedBy("monitor")
final Multiset<State> states = servicesByState.keys();
@GuardedBy("monitor")
final Map<Service, Stopwatch> startupTimers = Maps.newIdentityHashMap();
/**
* These two booleans are used to mark the state as ready to start. {@link #ready}: is set by
* {@link #markReady} to indicate that all listeners have been correctly installed {@link
* #transitioned}: is set by {@link #transitionService} to indicate that some transition has
* been performed.
*
* <p>Together, they allow us to enforce that all services have their listeners installed prior
* to any service performing a transition, then we can fail in the ServiceManager constructor
* rather than in a Service.Listener callback.
*/
@GuardedBy("monitor")
boolean ready;
@GuardedBy("monitor")
boolean transitioned;
final int numberOfServices;
/**
* Controls how long to wait for all the services to either become healthy or reach a state from
* which it is guaranteed that it can never become healthy.
*/
final Monitor.Guard awaitHealthGuard =
new Monitor.Guard(monitor) {
@Override
public boolean isSatisfied() {
// All services have started or some service has terminated/failed.
return states.count(RUNNING) == numberOfServices
|| states.contains(STOPPING)
|| states.contains(TERMINATED)
|| states.contains(FAILED);
}
};
/** Controls how long to wait for all services to reach a terminal state. */
final Monitor.Guard stoppedGuard =
new Monitor.Guard(monitor) {
@Override
public boolean isSatisfied() {
return states.count(TERMINATED) + states.count(FAILED) == numberOfServices;
}
};
/** The listeners to notify during a state transition. */
@GuardedBy("monitor")
final List<ListenerCallQueue<Listener>> listeners =
Collections.synchronizedList(new ArrayList<ListenerCallQueue<Listener>>());
/**
* It is implicitly assumed that all the services are NEW and that they will all remain NEW
* until all the Listeners are installed and {@link #markReady()} is called. It is our caller's
* responsibility to only call {@link #markReady()} if all services were new at the time this
* method was called and when all the listeners were installed.
*/
ServiceManagerState(ImmutableCollection<Service> services) {
this.numberOfServices = services.size();
servicesByState.putAll(NEW, services);
}
/**
* Attempts to start the timer immediately prior to the service being started via {@link
* Service#startAsync()}.
*/
void tryStartTiming(Service service) {
monitor.enter();
try {
Stopwatch stopwatch = startupTimers.get(service);
if (stopwatch == null) {
startupTimers.put(service, Stopwatch.createStarted());
}
} finally {
monitor.leave();
}
}
/**
* Marks the {@link State} as ready to receive transitions. Returns true if no transitions have
* been observed yet.
*/
void markReady() {
monitor.enter();
try {
if (!transitioned) {
// nothing has transitioned since construction, good.
ready = true;
} else {
// This should be an extremely rare race condition.
List<Service> servicesInBadStates = Lists.newArrayList();
for (Service service : servicesByState().values()) {
if (service.state() != NEW) {
servicesInBadStates.add(service);
}
}
throw new IllegalArgumentException(
"Services started transitioning asynchronously before "
+ "the ServiceManager was constructed: "
+ servicesInBadStates);
}
} finally {
monitor.leave();
}
}
void addListener(Listener listener, Executor executor) {
checkNotNull(listener, "listener");
checkNotNull(executor, "executor");
monitor.enter();
try {
// no point in adding a listener that will never be called
if (!stoppedGuard.isSatisfied()) {
listeners.add(new ListenerCallQueue<Listener>(listener, executor));
}
} finally {
monitor.leave();
}
}
void awaitHealthy() {
monitor.enterWhenUninterruptibly(awaitHealthGuard);
try {
checkHealthy();
} finally {
monitor.leave();
}
}
void awaitHealthy(long timeout, TimeUnit unit) throws TimeoutException {
monitor.enter();
try {
if (!monitor.waitForUninterruptibly(awaitHealthGuard, timeout, unit)) {
throw new TimeoutException(
"Timeout waiting for the services to become healthy. The "
+ "following services have not started: "
+ Multimaps.filterKeys(servicesByState, in(ImmutableSet.of(NEW, STARTING))));
}
checkHealthy();
} finally {
monitor.leave();
}
}
void awaitStopped() {
monitor.enterWhenUninterruptibly(stoppedGuard);
monitor.leave();
}
void awaitStopped(long timeout, TimeUnit unit) throws TimeoutException {
monitor.enter();
try {
if (!monitor.waitForUninterruptibly(stoppedGuard, timeout, unit)) {
throw new TimeoutException(
"Timeout waiting for the services to stop. The following "
+ "services have not stopped: "
+ Multimaps.filterKeys(
servicesByState, not(in(ImmutableSet.of(TERMINATED, FAILED)))));
}
} finally {
monitor.leave();
}
}
ImmutableMultimap<State, Service> servicesByState() {
ImmutableSetMultimap.Builder<State, Service> builder = ImmutableSetMultimap.builder();
monitor.enter();
try {
for (Entry<State, Service> entry : servicesByState.entries()) {
if (!(entry.getValue() instanceof NoOpService)) {
builder.put(entry.getKey(), entry.getValue());
}
}
} finally {
monitor.leave();
}
return builder.build();
}
ImmutableMap<Service, Long> startupTimes() {
List<Entry<Service, Long>> loadTimes;
monitor.enter();
try {
loadTimes = Lists.newArrayListWithCapacity(startupTimers.size());
// N.B. There will only be an entry in the map if the service has started
for (Entry<Service, Stopwatch> entry : startupTimers.entrySet()) {
Service service = entry.getKey();
Stopwatch stopWatch = entry.getValue();
if (!stopWatch.isRunning() && !(service instanceof NoOpService)) {
loadTimes.add(Maps.immutableEntry(service, stopWatch.elapsed(MILLISECONDS)));
}
}
} finally {
monitor.leave();
}
Collections.sort(
loadTimes,
Ordering.<Long>natural()
.onResultOf(
new Function<Entry<Service, Long>, Long>() {
@Override
public Long apply(Map.Entry<Service, Long> input) {
return input.getValue();
}
}));
ImmutableMap.Builder<Service, Long> builder = ImmutableMap.builder();
for (Entry<Service, Long> entry : loadTimes) {
builder.put(entry);
}
return builder.build();
}
/**
* Updates the state with the given service transition.
*
* <p>This method performs the main logic of ServiceManager in the following steps.
*
* <ol>
* <li>Update the {@link #servicesByState()}
* <li>Update the {@link #startupTimers}
* <li>Based on the new state queue listeners to run
* <li>Run the listeners (outside of the lock)
* </ol>
*/
void transitionService(final Service service, State from, State to) {
checkNotNull(service);
checkArgument(from != to);
monitor.enter();
try {
transitioned = true;
if (!ready) {
return;
}
// Update state.
checkState(
servicesByState.remove(from, service),
"Service %s not at the expected location in the state map %s",
service,
from);
checkState(
servicesByState.put(to, service),
"Service %s in the state map unexpectedly at %s",
service,
to);
// Update the timer
Stopwatch stopwatch = startupTimers.get(service);
if (stopwatch == null) {
// This means the service was started by some means other than ServiceManager.startAsync
stopwatch = Stopwatch.createStarted();
startupTimers.put(service, stopwatch);
}
if (to.compareTo(RUNNING) >= 0 && stopwatch.isRunning()) {
// N.B. if we miss the STARTING event then we may never record a startup time.
stopwatch.stop();
if (!(service instanceof NoOpService)) {
logger.log(Level.FINE, "Started {0} in {1}.", new Object[] {service, stopwatch});
}
}
// Queue our listeners
// Did a service fail?
if (to == FAILED) {
fireFailedListeners(service);
}
if (states.count(RUNNING) == numberOfServices) {
// This means that the manager is currently healthy. N.B. If other threads call isHealthy
// they are not guaranteed to get 'true', because any service could fail right now.
fireHealthyListeners();
} else if (states.count(TERMINATED) + states.count(FAILED) == numberOfServices) {
fireStoppedListeners();
}
} finally {
monitor.leave();
// Run our executors outside of the lock
executeListeners();
}
}
@GuardedBy("monitor")
void fireStoppedListeners() {
STOPPED_CALLBACK.enqueueOn(listeners);
}
@GuardedBy("monitor")
void fireHealthyListeners() {
HEALTHY_CALLBACK.enqueueOn(listeners);
}
@GuardedBy("monitor")
void fireFailedListeners(final Service service) {
new Callback<Listener>("failed({service=" + service + "})") {
@Override
void call(Listener listener) {
listener.failure(service);
}
}.enqueueOn(listeners);
}
/** Attempts to execute all the listeners in {@link #listeners}. */
void executeListeners() {
checkState(
!monitor.isOccupiedByCurrentThread(),
"It is incorrect to execute listeners with the monitor held.");
// iterate by index to avoid concurrent modification exceptions
for (int i = 0; i < listeners.size(); i++) {
listeners.get(i).execute();
}
}
@GuardedBy("monitor")
void checkHealthy() {
if (states.count(RUNNING) != numberOfServices) {
IllegalStateException exception =
new IllegalStateException(
"Expected to be healthy after starting. The following services are not running: "
+ Multimaps.filterKeys(servicesByState, not(equalTo(RUNNING))));
throw exception;
}
}
}