pyease-grpc

pyease-grpc

Easy to use gRPC-web client in python

Installation

Install the package using:

$ pip install pyease-grpc

Run the following to check if it has been installed correctly:

$ pyease-grpc --version

Tutorial

Before you start, you need to have a basic understanding of how gRPC works.

This package provides a requests like interface to make calls to native gRPC and gRPC-Web servers.

Example Server

An example server and client can be found in the example folder.

> cd example
> docker compose up

It uses two ports:

• Native gRPC server: localhost:50050
• gRPC-Web server using envoy: http://localhost:8080

You can test the native serve with the client:

$ python example/server/client.py
Calling SayHello:
reply: "Hello, world!"

Calling LotsOfReplies:
reply: "Hello, world no. 0!"
reply: "Hello, world no. 1!"
reply: "Hello, world no. 2!"
reply: "Hello, world no. 3!"
reply: "Hello, world no. 4!"

Calling LotsOfGreetings:
reply: "Hello, A, B, C!"

Calling BidiHello:
reply: "Hello, A!"
reply: "Hello, B!"
reply: "Hello, C!"

Loading the Protobuf

The proto file is located at example/server/abc.proto

// file: example/server/abc.proto
syntax = "proto3";

package pyease.sample.v1;

service Greeter {
  rpc SayHello (HelloRequest) returns (HelloResponse);
  rpc LotsOfReplies(HelloRequest) returns (stream HelloResponse);
  rpc LotsOfGreetings(stream HelloRequest) returns (HelloResponse);
  rpc BidiHello(stream HelloRequest) returns (stream HelloResponse);
}

message HelloRequest {
  string name = 1;
}

message HelloResponse {
  string reply = 1;
}

You can directly load this file using pyease_grpc without generating any stubs:

from pyease_grpc import Protobuf

protobuf = Protobuf.from_file("example/server/abc.proto")

Internally, it converts the proto file into FileDescriptorSet message.

It is recommended to use the FileDescriptorSet json to load the Protobuf faster.

To generate the FileDescriptorSet json from a proto file:

$ pyease-grpc -I example/server example/server/abc.proto --output abc_fds.json

Now you can use this descriptor file directly to create a Protobuf instance.

protobuf = Protobuf.restore_file('abc_fds.json')

Getting response from gRPC-Web

For Unary RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.request(
    RpcUri(
      base_url="http://localhost:8080",
      package="pyease.sample.v1",
      service="Greeter",
      method="SayHello",
    ),
    {
      "name": "world"
    },
)
response.raise_for_status()

print(response.single['reply'])

For a Server-side Streaming RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.request(
    RpcUri(
      base_url="http://localhost:8080",
      package="pyease.sample.v1",
      service="Greeter",
      method="LotsOfReplies",
    ),
    {
      "name": "world",
    },
)
response.raise_for_status()

for payload in response.iter_payloads():
    print(payload["reply"])

gRPC-Web currently supports 2 RPC modes: Unary RPCs, Server-side Streaming RPCs. Client-side and Bi-directional streaming is not currently supported.

Using the native gRPC protocol

You can also directly call a method using the native gRPC protocol.

For Unary RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.call(
    RpcUri(
      base_url="localhost:50050",
      package="pyease.sample.v1",
      service="Greeter",
      method="SayHello",
    ),
    {
      "name": "world",
    }
)

print(response.single["reply"])
print(response.payloads)

For a Server-side Streaming RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.call(
    RpcUri(
      base_url="localhost:50050",
      package="pyease.sample.v1",
      service="Greeter",
      method="LotsOfReplies",
    ),
    {
      "name": "world",
    },
)

for payload in response.iter_payloads():
    print(payload["reply"])
print(response.payloads)

For a Client-Side Streaming RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.call(
    RpcUri(
      base_url="localhost:50050",
      package="pyease.sample.v1",
      service="Greeter",
      method="LotsOfGreetings",
    ),
    iter(
      [
        {"name": "A"},
        {"name": "B"},
        {"name": "C"},
      ]
    ),
)

print(response.single["reply"])
print(response.payloads)

For a Bidirectional Streaming RPC request:

from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
response = session.call(
    RpcUri(
      base_url="localhost:50050",
      package="pyease.sample.v1",
      service="Greeter",
      method="BidiHello",
    ),
    iter(
      [
        {"name": "A"},
        {"name": "B"},
        {"name": "C"},
      ]
    ),
)

for payload in response.iter_payloads():
    print(payload["reply"])
print(response.payloads)

Error Handling

Errors are raised as soon as they appear.

List of errors that can appear during request:

• ValueError: If the requested method, service or package is not found
• requests.exceptions.InvalidHeader: If the header of expected length is not found
• requests.exceptions.ContentDecodingError: If the data of expected length is not found
• NotImplementedError: If compression is enabled in the response headers
• grpc.RpcError: If the grpc-status is non-zero

List of errors that can appear during call:

• ValueError: If the requested method, service or package is not found
• grpc.RpcError: If the grpc-status is non-zero

To get the grpc-status and grpc-message, you can add a try-catch to your call. e.g.:

import grpc
from pyease_grpc import RpcSession, RpcUri

session = RpcSession.from_file("example/server/abc.proto")
rpc_uri = RpcUri(
  base_url="localhost:50050",
  package="pyease.sample.v1",
  service="Greeter",
  method="SayHello",
)
try:
  response = session.call(rpc_uri, {"name": "error"})
  print(response.single["reply"])
except grpc.RpcError as e:
  print('grpc status', e.code())
  print('grpc message', e.details())