gRPC command line tool

Overview

This document describes the command line tool that comes with gRPC repository. It is desirable to have command line tools written in other languages roughly follow the same syntax and flags.

At this point, the tool needs to be built from source, and it should be moved out to grpc-tools repository as a stand alone application once it is mature enough.

Core functionality

The command line tool can do the following things:

  • Send unary rpc.
  • Attach metadata and display received metadata.
  • Handle common authentication to server.
  • Infer request/response types from server reflection result.
  • Find the request/response types from a given proto file.
  • Read proto request in text form.
  • Read request in wire form (for protobuf messages, this means serialized binary form).
  • Display proto response in text form.
  • Write response in wire form to a file.

The command line tool should support the following things:

  • List server services and methods through server reflection.
  • Fine-grained auth control (such as, use this oauth token to talk to the server).
  • Send streaming rpc.

Code location

To use the tool, you need to get the grpc repository and make sure your system has the prerequisites for building grpc from source, given in the installation instructions.

In order to build the grpc command line tool from a fresh clone of the grpc repository, you need to run the following command to update submodules:

git submodule update --init

You also need to have the gflags library installed on your system. On Linux systems, gflags can be installed with the following command:

sudo apt-get install libgflags-dev

Once the prerequisites are satisfied, you can build the command line tool with the command:

$ make grpc_cli

The main file can be found at https://github.com/grpc/grpc/blob/master/test/cpp/util/grpc_cli.cc

Usage

Basic usage

Send a rpc to a helloworld server at localhost:50051:

$ bins/opt/grpc_cli call localhost:50051 SayHello "name: 'world'" \
    --enable_ssl=false

On success, the tool will print out

Rpc succeeded with OK status
Response:
 message: "Hello world"

The localhost:50051 part indicates the server you are connecting to. SayHello is (part of) the gRPC method string. Then "name: 'world'" is the text format of the request proto message. We are not using ssl here by --enable_ssl=false. For information on more flags, look at the comments of grpc_cli.cc.

Use local proto files

If the server does not have the server reflection service, you will need to provide local proto files containing the service definition. The tool will try to find request/response types from them.

$ bins/opt/grpc_cli call localhost:50051 SayHello "name: 'world'" \
    --protofiles=examples/protos/helloworld.proto --enable_ssl=false

If the proto files is not under current directory, you can use --proto_path to specify a new search root.

Send non-proto rpc

For using gRPC with protocols other than probobuf, you will need the exact method name string and a file containing the raw bytes to be sent on the wire

$ bins/opt/grpc_cli call localhost:50051 /helloworld.Greeter/SayHello --input_binary_file=input.bin \
    --output_binary_file=output.bin

On success, you will need to read or decode the response from the output.bin file.