Major Description
This issue will track the implementation of how to handle the memory pressure for secondary region replicas. Since the replicas cannot flush by themselves, the region server might get blocked or cause extensive flushing for its primary regions. The design doc attached at HBASE-11183 contains two possible solutions that we can pursue. The first one is to not allow secondary region replicas to not flush by themselves, but instead of needed allow them to refresh their store files on demand (which possibly allows them to drop their memstore snapshots or memstores). The second approach is to allow the secondaries to flush to a temporary space.
Both have pros and cons, but for simplicity and to not cause extra write amplification, we have implemented the first approach. More details can be found in the design doc, but we can also discuss other options here.