Hi, Igniters, I want to raise a topic about our affinity node definition.
After adding baseline (affinity) topology (BL(A)T) things start being complicated. Plenty of bugs appears: IGNITE-8173 ignite.getOrCreateCache(cacheConfig).iterator() method works incorrect for replicated cache in case if some data node isn't in baseline IGNITE-7628 SqlQuery hangs indefinitely with additional not registered in baseline node. It's because everything relies on concept "affinity node". And until now it was as simple as a server node which passes node filter. Other words any server node which is not filtered out by node filter. But node which is not in BL(A)T and which passes node filter would be treated as affinity node. And it's definitely wrong. At least, it is a source of many bugs (I believe there are much more than those 2 which I already have mentioned). It's clear that this definition should be changed. Let's start with a new definition of "Affinity topology". Affinity topology is a set of nodes which potentially could keep data. If we use knowledge about the current realization we can say that 1. for in-memory cache groups it would be all server nodes; 2. for persistent cache groups it would be BL(A)T. I will further use Dynamic Affinity Topology or DAT for 1 (in-memory cache groups) and Static Affinity Topology or SAT instead BL(A)T, or 2nd point. Denote node filter as f(X), where X is affinity topology. Then we can say that node A is affinity node if A ∈ AT', where AT' = f(AT), where AT is DAT or SAT. It worth to mention that AT' should be used to pass to affinity function of cache groups. Also, AT and AT' could change during the time (BL(A)T changes or node joins/disconnections). And I don't like fact that usage of DAT or SAT relies on persistence settings (Should we make it configurable per cache group?). Ok, I have created a ticket to implement this changes and will start working on it. https://issues.apache.org/jira/browse/IGNITE-8380 (Affinity node calculation doesn't take into account BLT). Also, I want to use these definitions (Affinity Topology, Affinity Node, DAT, SAT) in documentation and java docs. Maybe, we also should consider replacing BL(A)T with SAT. Thank you for your attention.
