Hi Val. Do you have an idea what is causing the NPE in the first place?
As Andrey says the exception is caused because of different topology versions cluster nodes. > What is null? > Node is null in the following code in org.apache.ignite.internal.processors.cache.query.ScanQueryFallbackClosableIterator.init(): 710: final ClusterNode node = nodes.poll(); 711: 712: if (*node*.isLocal()) { and nodes found as: private Queue<ClusterNode> fallbacks(AffinityTopologyVersion topVer) { Deque<ClusterNode> fallbacks = new LinkedList<>(); Collection<ClusterNode> owners = new HashSet<>(); for (ClusterNode node : cctx.topology().owners(part, topVer)) { if (node.isLocal()) fallbacks.addFirst(node); else fallbacks.add(node); owners.add(node); } for (ClusterNode node : cctx.topology().moving(part)) { if (!owners.contains(node)) fallbacks.add(node); } return fallbacks; } It is clear that if topology versions are different NPE is expected. But my claim is NPE can occur without any change in topology versions. In the example/dummy code NPE happens before any change in topology versions on cluster. But I could not convince him about that :) Or I am missing somthing really badly. Thanks all of you. Regards. -- Alper Tekinalp Software Developer Evam Streaming Analytics Atatürk Mah. Turgut Özal Bulv. Gardenya 5 Plaza K:6 Ataşehir 34758 İSTANBUL Tel: +90 216 455 01 53 Fax: +90 216 455 01 54 www.evam.com.tr <http://www.evam.com>