[IGNITE-426] Make sure continuous queries notifications are not missed in case primary node fails

• Type: Sub-task
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 1.5.0.final
• Component/s: cache
• Labels: cq_todo important
• Assignee: Nikolay Tikhonov
• Reporter: Yakov Zhdanov
• Created: 06/Mar/15 13:32
• Updated: 30/May/20 15:36
• Resolved: 19/Nov/15 18:21

Description

• 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.
• To cleanup the backup queue we will use communication acks. When batch receival is acked by the client, we will send special ack message to backup nodes that will remove items that are not longer needed. This message has to contain partition to latest update counter map.

Issue Links

• is blocked by: IGNITE-104 Need to enable thread-per-partition mode for atomic caches
• is related to: IGNITE-1897 Add failover to write-behind cache store
• relates to: IGNITE-4029 Local ContinuousQueries on PARTITIONED caches may await for previously rejected events