[bailey-developers] Features and their design

[Ning L. <nin...@gm...>]

Here are the main features discussed so far:
1 Load balancing by using consistent hashing.
2 Fault tolerance by replications.
3 Online update by making all replicas updateable.
4 Eventual consistency.
  - An update is sent to W replicas before it completes.
  - Assume an application specifies doc version number.
  - Using the terms in [1], we should support session
    consistency and monotonic write consistency, and
    maybe read-your-writes and monotonic read consistency.
5 A document database?
  - We store documents anyway.
  - We don't support sub-document updates.
  - Do we support document versioning? Other features?

Here are a few comments on the features:
1 Consistent hashing uses hash values because hash values
  distribute uniformly on the ring. Can we support
  application-specified keys for the ring? The difference
  is that the distribution may not be uniform so we need
  to rebalance sometimes (remove a virtual node and insert
  it somewhere else).
1 On the assumption that an application specifies document
  version number. It greatly simplifies things, but is
  it practical?
2 How much a document database we want it to be? I'm not
  sure if CouchDB is a typical document database...


Design for the features is to come...

Ning