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INTEGRATION.md

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Rockette example gRPC integration

Introduction

Rockette comes with a basic example of a gRPC integration. The interface is described in rkt/proto/rkt.proto, which describes the RocketteService. This allows applications written in any of the languages supported by gRPC to send/receive data from the Rockette application, on the same host or through the network.

RocketteService

Looking at rkt/proto/rkt.proto, we have:

service RocketteService {
  rpc UpdateIntData (IntValue) returns (StatusResponse) {}
  rpc UpdateFloatData (FloatValue) returns (StatusResponse) {}
  rpc UpdateStringData (StringValue) returns (StatusResponse) {}
  rpc UpdateBytesData (BytesValue) returns (StatusResponse) {}
}

Each of these methods receive an argument with an identifier (string), and a value (with matching types).

This service is implemented in src/RocketteService.cpp. This file contains the class responsible for handling the RPC calls. The base implementation has a std::map<string, type> for each type, and stores the value with the identifier key. These can then be retrieved from the RocketteService class through the public accessor methods:

int getIntValue(std::string identifier, int& result);
int getIntValueAsString(std::string identifier, std::string& result);
int getFloatValue(std::string identifier, float& result);
int getFloatValueAsString(std::string identifier, std::string& result, int precision = 0);
int getStringValue(std::string identifier, std::string& result);
int getBytesValue(std::string identifier, std::string& result);

This way you can retrieve data sent to your graphical application by other applications.

Generating gRPC code, a Python example

To create a new application that's able to make RPC calls in our Rockette application, you should generate the base implementation from the rkt.proto file.

First, make sure you have all the dependencies described by the documentation.

Then, from rkt/proto/, run:

python -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. rkt.proto

This command will generate two new files: rkt_pb2_grpc.py and rkt_pb2.py. You will need to update these files every time the rkt.proto file is modified.

In integration/examples/python, there is an example of how to use these files to make RPC calls. Make sure to update the config.json file to connect to the correct host.

To run the rkt-control example, run:

python main.py