We have different priority in RPC level, we can even separate write requests and read requests to different handlers. But, yes, the WAL uses FIFO queue, and even more, we use a single thread to consume the append and sync requests. The reason is that we need to keep the sequenceID of WAL entry to increase monotonically, otherwise, data will can be loss when replaying or replicating. The sequenceID is assigned when the WAL entry was queued, it is impossible to serve a 'priority' request comes later without breaking the order. However, if requests are from different table, I think you can add a new WALProvider to separate the table's WAL from others to achieve better Isolation. Best Regards Allan Yang
Jing Liu <[email protected]> 于2018年11月8日周四 上午5:49写道： > Hi, > > I'am trying to add priority to schedule different types of requests in > HBase. But the Write-ahead logging use RingBuffer which > is essentially a FIFO queue makes it hard. In this case, let's say if the > low priority request already queued in the RingBuffer, the high priority > request can not be executed before all those queued low priority request. > I'm wondering if I change the FIFO queue into Priority-based queue > will violate the write consistency guarantee or other issues? > > Thanks, > Jing >
