Numerical C++ Demo with gRPC and Docker

Performances

The generated performance report can be seen here:

https://sirehna.github.io/waves_gRPC.

How to run it

make

• make cpp-perf-test: Runs benchmarks for various ways of encoding the wave data. This was used to choose the proto definition for the wave services.
• make gtest: Illustrates how we can use gRPC from google test
• make ghz-perf-test: Uses ghz to measure the gRPC server's general performance

The client sends a request to the server with parameters x, y and t, the server computes the elevation z (using hard-coded discrete wave spectrum values), and sends it back.

Example adapted from https://grpc.io/docs/tutorials/basic/c.html#example-code-and-setup demo.

.proto file

wave.proto

This file defines the data structures and the RPC services.

Unary implementation

• Files concerned: wave_client and wave_server
• Service concerned: GetElevation

Here the client can send a set of Points (x, y) in one request. The server computes the elevation for each Point and sends back the array of results.

In protubuf, the key-word repeated is used to represent an array. The generated functions used to decode data after it is sent are slightly different : see https://developers.google.com/protocol-buffers/docs/reference/cpp-generated#repeatednumeric.

In order for the server to compute the discrete wave spectrum value once and not at each request, it is computed in the main of the server, and passed as an argument of the service. To do so :

• a spectrum value attribute is defined in the server service class
• the server service class constructor getting this value as a parameter is defined (with the explicit keyword), and sets it.

Server streaming implementation

• Files concerned: wave_client and wave_server
• Service concerned: GetElevations

Here the client can now send t_start, t_end and dt values with the set of Points (x, y), in its request. The server sends a stream of elevation arrays: one for each t within the time interval asked by the client. To do so :

• keyword stream in service definition.
• use grpc::ServerWriter to write stream and grpc::ClientReader to read it.