Igniters, Based on discussions with our users I came to conclusion that our continuous query implementation is not good enough for use cases with strong consistency requirements, because there is a possibility to lose updates in case of topology change.
So I started working on https://issues.apache.org/jira/browse/IGNITE-426 and I hope to finish in in couple of weeks so that we can include it in next release. I have the following design in mind: - Maintain updates queue on backup node(s) in addition to primary node. - If primary node crushes, this queue is flushed to listening clients. - To avoid notification duplicates we will have a per-partition update counter. Once an entry in some partition is updated, counter for this partition is incremented on both primary and backups. The value of this counter is also sent along with the update to the client, which also maintains the copy of this mapping. If at some moment it receives an update with the counter less than in its local map, this update is a duplicate and can be discarded. - Also need to figure out the best way to clean the backup queue if topology is stable. Will be happy to hear any suggestions :) To make all this work we also need to implement thread-per-partition mode in atomic cache, because now updates order on backup nodes can differ from the primary node: https://issues.apache.org/jira/browse/IGNITE-104. I'm already working on this. Feel free to share your thoughts! -Val
