Using validation implemented in
IGNITE-7467 we can observe the following situation:
Let's we have some partition and nodes which owning it N1 (primary) and N2 (backup)
1) Exchange is started
2) N2 finished waiting for partitions release and started to create Single message (with update counters).
3) N1 waits for partitions release.
4) We have pending cache update N1 -> N2. This update is done after step 2.
5) This update increments update counters both on N1 and N2.
6) N1 finished waiting for partitions release, while N2 already sent Single message to coordinator with outdated update counter.
7) Coordinator sees different partition update counters for N1 and N2. Validation is failed, while data is equal.
Every server node participating in PME should wait while all other server nodes will finish their ongoing updates (finish wait for partition release method)