java - How to tailor existing MongoDB peacefully? -

supose have running mongodb instance(also using mongo sharding) millions of data , thousand of transactions per second, , have used morphia object-document mappe. since want keep project alive bug fixing, updating , ... in point changing data model inevitable. consider below example : have persisted class (model) :

private eventasset{     @id     private string id;     @constraints.required     private string time;     private eventtype eventtype; } 

and have decided eventasset.class should change :

private eventasset{     @id     private string id;     @constraints.required     private string time;     @constraints.required     private string assetname; } 

as can see eventtype has been removed , required assetname added, , changes prevent application starting. major possible solutions can think of are

• create new db , insert old values , how manage switch between old , new db in way wont harm incomming few thousant transactions per second.
• use or create tool analyse class , compare against database , make necessary changes existing db , cause no harm exisitng data , incomming data flow (few thousant transaction per second)

this scenario seems every day (or @ least every few months or so) problem every live project. there accepted solution problem? suggest?

removing @constraints.required shouldn't problem , adding new attribute fine well. app won't start because of @constraints.required — ist annotation play framework?

i'd think requirement pretty same in relational databases — add new column, make required, , won't work longer.

possible solutions i'd see:

• drop annotation , enforce logic new writes in application
• have cleanup application adds value existing data (if that's possible). add annotation once value exists on entries.
• use multiple datastores if must — not sure if worth overhead. , use @ least morphia 1.0.0-rc0, because there has been bug before multiple datastores in single application.