private Observable<V> fromMemory(User user, K key) {
UserMemoryCache<K, V> userMemoryCache = userMemoryCaches.get(user);
if (!userMemoryCache.containsKey(key)) {
return Observable.empty();
} else {
Pair<Long, V> cachedValue = userMemoryCache.get(key);
long cachedSince = DateUtils.getCurrentTimestamp() - cachedValue.first;
if (cachedSince < staleThreshold) {
return Observable.just(userMemoryCache.get(key).second);
} else {
// Value has expired
userMemoryCache.remove(key);
return Observable.empty();
}
}
}
private void saveToMemory(User user, K key, V value) {
long currentTimestamp = DateUtils.getCurrentTimestamp();
getUserCache(user).put(key, value, currentTimestamp);
}