netflix.ocelli.FailureDetectingInstance Maven / Gradle / Ivy
package netflix.ocelli;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import rx.Observable;
import rx.Subscriber;
import rx.functions.Action0;
import rx.functions.Func1;
import rx.functions.Func2;
/**
* Instance whose up state is dictated by a connector and failure detector.
*
* @author elandau
*
* @param
*/
public class FailureDetectingInstance extends Instance {
static class State {
private AtomicBoolean connected = new AtomicBoolean(true);
private AtomicInteger failureCounter = new AtomicInteger(-1);
static Func2 Accum = new Func2() {
@Override
public State call(State current, Throwable error) {
return current;
}
};
}
public FailureDetectingInstance(
final T value,
final Func1> connector,
final Observable errorStream,
final Func1 backoffStrategy
) {
super(value, new OnSubscribe() {
Observable lifecycle = Observable
// Placeholder to trigger for connect attempt
.just(new Throwable("Not connected"))
.concatWith(errorStream)
.scan(new State(), State.Accum)
// Skip the first element since scan() duplicates the first State
.skip(1)
// Discard errors while trying to connect
.filter(new Func1() {
@Override
public Boolean call(State state) {
return state.connected.compareAndSet(true, false);
}
})
.switchMap(new Func1>() {
@Override
public Observable call(final State state) {
return Observable
// Carry the 'false' to the subscribers
.just(false)
// Concat with connection logic
.concatWith(Observable
.just(state)
// Connect with backoff if necessary
.concatMap(new Func1>() {
@Override
public Observable call(State t1) {
int counter = state.failureCounter.incrementAndGet();
Observable connect = connector.call(value);
if (counter > 0) {
connect = connect.delaySubscription(backoffStrategy.call(counter), TimeUnit.MILLISECONDS);
}
return connect;
}
})
// Retry on all connect errors. Backoff counter will increase for each connect attempt.
.retry()
// Reset state to connected
.doOnCompleted(new Action0() {
@Override
public void call() {
if (state.connected.compareAndSet(false, true)) {
state.failureCounter.set(0);
}
}
})
// Emit 'true' to indicate instance is up
.cast(Boolean.class)
.defaultIfEmpty(true));
}
})
.replay(1)
.refCount();
@Override
public void call(Subscriber s) {
lifecycle.subscribe(s);
}
});
}
}