Apache IoTDB: integration with gRPC

Background:

Apache IoTDB uses Thrift as its RPC layer. However, there are some voices in the community: do we need to support gPRC?

We noticed:

• thrift has to apply memory for each RPC call (get data from the network into a byte array, and then convert the bytes to objects), and it is hard to control the whole memory cost for large RPC.
• thrift connection may be broken when there are too many concurrent connections.
• thrift does not support stream mode

So, we'd like to know whether gRPC is better.

Tasks:

• implement IoTDB's RPC layer using gRPC.
  • including the sync/async mode 
  • sub-tasks: the C++, c#, python API wrappers are also desired. 
• have a performance test
  • throughput, memory cost and jitter, etc..
• write a report to compare them

References:

iotdb's current thrift RPC specification:

1.  https://github.com/apache/iotdb/tree/master/thrift
2. there are some on-going thrift apis: thrift-datanode, thrift-confignode, thrift-cluster, thrift-sync