private AntiEntropyResponse handleAntiEntropyAdvertisement(AntiEntropyAdvertisement<K> ad) {
if (destroyed || underHighLoad()) {
return AntiEntropyResponse.IGNORED;
}
try {
if (log.isTraceEnabled()) {
log.trace(
"Received anti-entropy advertisement from {} for {} with {} entries in it",
ad.sender(),
mapName,
ad.digest().size());
}
antiEntropyCheckLocalItems(ad).forEach(this::notifyListeners);
} catch (Exception e) {
log.warn("Error handling anti-entropy advertisement", e);
return AntiEntropyResponse.FAILED;
}
return AntiEntropyResponse.PROCESSED;
}
/**
* Processes anti-entropy ad from peer by taking following actions: 1. If peer has an old entry,
* updates peer. 2. If peer indicates an entry is removed and has a more recent timestamp than the
* local entry, update local state.
*/
private List<EventuallyConsistentMapEvent<K, V>> antiEntropyCheckLocalItems(
AntiEntropyAdvertisement<K> ad) {
final List<EventuallyConsistentMapEvent<K, V>> externalEvents = Lists.newLinkedList();
final NodeId sender = ad.sender();
final List<NodeId> peers = ImmutableList.of(sender);
Set<K> staleOrMissing = new HashSet<>();
Set<K> locallyUnknown = new HashSet<>(ad.digest().keySet());
items.forEach(
(key, localValue) -> {
locallyUnknown.remove(key);
MapValue.Digest remoteValueDigest = ad.digest().get(key);
if (remoteValueDigest == null || localValue.isNewerThan(remoteValueDigest.timestamp())) {
// local value is more recent, push to sender
queueUpdate(new UpdateEntry<>(key, localValue), peers);
} else if (remoteValueDigest != null
&& remoteValueDigest.isNewerThan(localValue.digest())
&& remoteValueDigest.isTombstone()) {
// remote value is more recent and a tombstone: update local value
MapValue<V> tombstone = MapValue.tombstone(remoteValueDigest.timestamp());
MapValue<V> previousValue =
removeInternal(key, Optional.empty(), Optional.of(tombstone));
if (previousValue != null && previousValue.isAlive()) {
externalEvents.add(
new EventuallyConsistentMapEvent<>(mapName, REMOVE, key, previousValue.get()));
}
} else if (remoteValueDigest.isNewerThan(localValue.digest())) {
// Not a tombstone and remote is newer
staleOrMissing.add(key);
}
});
// Keys missing in local map
staleOrMissing.addAll(locallyUnknown);
// Request updates that we missed out on
sendUpdateRequestToPeer(sender, staleOrMissing);
return externalEvents;
}