Hello Igniters!
I have found some confusing behavior of atomic partitioned cache with
`PRIMARY_SYNC` write synchronization mode.
Node with a primary partition sends a message to remote nodes with backup
partitions via `GridDhtAtomicAbstractUpdateFuture#sendDhtRequests`.
If during of sending occurs an error then it, in fact, will be ignored, see
[1]:
```
try {
....
cctx.io().send(req.nodeId(), req, cctx.ioPolicy());
....
}
catch (ClusterTopologyCheckedException ignored) {
....
registerResponse(req.nodeId());
}
catch (IgniteCheckedException ignored) {
....
registerResponse(req.nodeId());
}
```
This behavior results in the primary partition and backup partitions have
the different value for given key.
There is the reproducer [2].
Should we consider this behavior as valid?
[1].
https://github.com/dgarus/ignite/blob/d473b507f04e2ec843c1da1066d8908e882396
d7/modules/core/src/main/java/org/apache/ignite/internal/processors/cache/di
stributed/dht/atomic/GridDhtAtomicAbstractUpdateFuture.java#L473
[2].
https://github.com/apache/ignite/pull/4126/files#diff-5e5bfb73bd917d85f56a05
552b1d014aR26
