Distributed Channel Cache: Design Notes

The overall goal for a distributed channel cache is to remove the responsibility for each Sync Gateway node to maintain a local in-memory channel cache of all changes seen in the cluster, as this limits our ability to scaling out a SG cluster.

• Background on current channel cache functionality
  • Description of all the functionality performed by the current in-memory cache - both the change cache, and the individual channel caches. Includes background on sequence buffering, deduplication.
• Initial proof-of-concept - design notes
  • Overview of the design for the initial POC, which is intended to validate some of the initial assumptions about whether moving the channel cache to a memcached bucket allows us to scale out Sync Gateway cache readers in the way we expect.
• Next Steps - what needs to be done beyond the initial POC
  • Addresses the features that were excluded from the initial POC.