empty_replica.java

// Create observable for master and all the replicas
// The code maps it to a tuple where the boolean represents "found!"
// so if its not found the tuple will be <False, null> and if its found <True, JsonDocument>

Observable<Tuple2<Boolean, JsonDocument>> primary = bucket.async()
    .get("doc")
    .map(doc -> Tuple.create(true, doc))
    .defaultIfEmpty(Tuple.create(false, null));

Observable<Tuple2<Boolean, JsonDocument>> first = bucket.async()
    .getFromReplica("doc", ReplicaMode.FIRST)
    .map(doc -> Tuple.create(true, doc))
    .defaultIfEmpty(Tuple.create(false, null));

Observable<Tuple2<Boolean, JsonDocument>> second = bucket.async()
    .getFromReplica("doc", ReplicaMode.SECOND)
    .map(doc -> Tuple.create(true, doc))
    .defaultIfEmpty(Tuple.create(false, null));

Observable<Tuple2<Boolean, JsonDocument>> third = bucket.async()
    .getFromReplica("doc", ReplicaMode.THIRD)
    .map(doc -> Tuple.create(true, doc))
    .defaultIfEmpty(Tuple.create(false, null));


// Since we now get an event even if no document is found, indicated by the boolean 
// in the tuple we just take the first one, it could be "false" with no doc attached
// to it. This could be then blocked on with an iterator or consumed as a single value
// too.

Observable<Tuple2<Boolean, JsonDocument>> firstFound = Observable
    .merge(primary, first, second, third)
    .first();