YCSB Collection Implementation

Here are some options I tried implementing collections in YCSB

Option 1 :

Initiate multiple threads per client and each thread open's exactly once collection
or multiple threads on connects/opens single collection

https://github.com/couchbaselabs/YCSB/tree/couchbase3-collection
(still needs some consmetic changes ... but works fine as expected)

Drawback : Cannot have single thread mutate on multiple collections

Option2 :

Initiate multiple threads with static variables and open cluster connection in read/update/insert method onto random collection and close environment/cluster connection at the end of READ/UPDATE/INSERT operation .

Drawback : Severe performance overhead of initiating multiple connection & close connections . Resulting in timeouts .

Option3:

Initiate multiple threads with static variables and cluster option . mutate on random collections in db.Read/update method by initiatialising collections
This resulted in nullpointerExceptions .
 
 
Is there a better way of implementing it ?
Also from SDK perspective.. I was wondering is having an option to pass collection as part of Bucket config a better way as compared to have Collection class in terms of application design and usability for developers/end users ?? 

Appreciate your feedback .

Base ycsb Branch - https://github.com/couchbaselabs/YCSB/commits/couchbase3-new-durability