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Transfer CDM files using Remote Procedure Calls.

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A python API for transferring Common Data Model (CDM) files using Remote Procedure Calls.




Create Environment

To activate the conda environment we'll use the environment.yml file. If you don't have conda installed on your machine, install if following these instructions. Start by cloning the repo and creating/activating the conda environment:

git clone
cd netcdf-grpc
conda env create --name [environment name] -f environment.yml
conda activate [environment name]

Note that you can omit the --name flag and the environment will default to netcdf-grpc-env.

Encode/Decode API

This demonstrates how to encode/decode gRPC messages within a python shell:

# import/instantiate encoder object
from src.netcdf_encode import netCDF_Encode
encoder = netCDF_Encode()

# import and define header request
import src.protogen.gcdm_netcdf_pb2 as grpc_msg
file_loc = "test/data/"
header_request = grpc_msg.HeaderRequest(location=file_loc)
header_response = encoder.generate_header_from_request(header_request)

# define data request
var_spec = "analysed_sst"
data_request = grpc_msg.DataRequest(location=file_loc, variable_spec=var_spec)
data_response = encoder.generate_data_from_request(data_request)

# decode header/data into xarray object
from src.netcdf_decode import netCDF_Decode
decoder = netCDF_Decode()
ds = decoder.generate_file_from_response(header_response, data_response)

Transfer Files using gRPC

This demonstrates how to implement the python encode/decode API and transmit netCDF files via gRPC. Start by opening up two separate tabs in your terminal. Make sure that whatever python environment you installed the requirements into is active in both. Make sure that you are in base folder of this repo.

In the first tab, start the gRPC server by running the following command:


If it is working properly you should see something that says starting server....

In the second tab, make a client request by running the following command:


Something resembling an xarray dataset should print to the terminal if everything is working. Feel free to modify the loc and variable_spec variables in to modify what data is transmitted.

Generating Python Source Code from proto Files

In order to generate the grpc python source code from the .proto files in protos/src/protogen, we need to use the protoc compiler (the reason for the weird subfolder structure is so that protoc generates files with proper import namespaces). The python package with protoc can be installed by following the instructions here.

To compile our code, and put the resulting functions into src/protogen/, we can use the following commands (from the root directory where this README is located):

$ python -m grpc_tools.protoc -I protos/ --python_out=. --grpc_python_out=. protos/pygcdm/protogen/*.proto

More information on the protoc compiler can be found by loading the module in python and using the help command:

$ python
>>> import grpc_tools.protoc
>>> help(grpc_tools.protoc)

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