We are also interested in this.
Worked on a prototype with having one HLog instance but underlying there will be multiple writer instances. The regions will be allocated with any one of the writer instance and each region will be writing to hlog using the instance associated with it.
Even on logrolling the instances against each region will be updated and the region will continue to use its mapping.
It is a 3 node cluster and the size of each record was 1k. No of regions : 2800
By default used 3 writer instances. I was able to pass the testcases related to TestHlog and TestDistributedLogSplitting. But Testmasterreplication was not passing.
Replication needs some change based on this which i did not work on much.
The pendingWrites list that we use is now converted into a map having the writer with the list of pending writes.
Pls provide your suggestions on this.
BTW, Li Pi, any progress on this? I would love to help you in this.
May be i can prepare a more forma patch and upload over here.