grpc-promise



Table of contents

- What's gRPC
- Introduction to grpc-promise
- Installation
- API by example
- Proto example file
- Unary Request
- Client Stream Request
- Server Stream Request
- Bidirectional Stream Request
- Request with Metadata
- Using Deadline
- Promisify single function
- MIT License

What's gRPC?

High performance, open source, general-purpose RPC framework.

Calling service types

- Simple RPC: one single asynchronous call
- Streaming RPC: one stream is used for the call

Implementations

- Unary Request: One single message request, one single message response
- Client Stream Request: One Writable stream message request, one single message response, sent once the stream is closed
- Server Stream Request: One single message request, one Readable stream message response
- Bidirectional Stream Request: One Duplex stream for request and response

Introduction to grpc-promise

GRPC promisify module for all Request/Response types: standard and stream.

This module unifies the way the grpc are implemented in NodeJS.

Depending on which kind of RPC call is implemented (simple vs streaming), we need to manage communication differently:
- Simple RPC: sending message and setting callbacks for responses
- Streaming RPC: opening stream and managing stream events to write and read messages

The goal of grpc-promise is to standardize all kind of calls, whatever they are, from the client side.

Installation

``bash
$ npm install grpc-promise
`

API by example

- Test proto file test.proto
- Complete GRPC Server implementation server.js
- All kind of GRPC Client implementations:
- Unary Request Example client-unary.js
- Client Stream Request Example client-client-stream.js
- Server Stream Request Example client-server-stream.js
- Bidirectional Stream Request Example client-bidi-stream.js

$3

Let's take a simple proto file exposing all kind of requests:

`bash
syntax = "proto3";

package test;

service Test {

rpc TestStreamSimple (stream TestRequest) returns (TestResponse) {}

rpc TestSimpleStream (TestRequest) returns (stream TestResponse) {}

rpc TestSimpleSimple (TestRequest) returns (TestResponse) {}

rpc TestStreamStream (stream TestRequest) returns (stream TestResponse) {}

}

message TestRequest {
int32 id = 1;
}

message TestResponse {
int32 id = 1;
}
`

$3

Implementation of TestSimpleSimple message

Server side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

const testSimpleSimple = function (call, callback) {
console.log('Server: Simple Message Received = ', call.request); // Server: Simple Message Received = {id: 1}
callback(null, call.request);
};

main = function () {
server = new grpc.Server();
server.addService(test_proto.Test.service, {
testSimpleSimple: testSimpleSimple
});

server.bind('0.0.0.0:50052', grpc.ServerCredentials.createInsecure());
server.start();
}

main();
`

Client side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const grpc_promise = require('grpc-promise');;

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

grpc_promise.promisifyAll(client);

client.testSimpleSimple()
.sendMessage({id: 1})
.then(res => {
console.log('Client: Simple Message Received = ', res) // Client: Simple Message Received = {id: 1}
})
.catch(err => console.error(err))
;
}

main();
`

$3

Implementation of TestStreamSimple message

Server side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

const testStreamSimple = function (call, callback) {
var messages = [];
call.on('data', function (m) {
console.log('Server: Stream Message Received = ', m); // Server: Stream Message Received = {id: 1}
messages.push(m);
});
call.on('end', function () {
callback(null, messages.pop());
});
};

main = function () {
server = new grpc.Server();
server.addService(test_proto.Test.service, {
testStreamSimple: testStreamSimple
});

server.bind('0.0.0.0:50052', grpc.ServerCredentials.createInsecure());
server.start();
}

main();
`

Client side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const grpc_promise = require('grpc-promise');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

grpc_promise.promisifyAll(client);

client.testStreamSimple()
.sendMessage({id: 1})
.sendMessage({id: 2})
.sendMessage({id: 3})
.end()
.then(res => {
console.log('Client: Simple Message Received = ', res); // Client: Simple Message Received = {id: 3}
})
.catch(err => console.error(err))
;
}

main();
`

$3

Implementation of TestSimpleStream message

Server side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

const testSimpleStream = function (call) {
console.log('Server: Simple Message Received = ', call.request); // Server: Simple Message Received = {id: 1}
call.write(call.request);
call.write(call.request);
call.end();
};

main = function () {
server = new grpc.Server();
server.addService(test_proto.Test.service, {
testSimpleStream: testSimpleStream
});

server.bind('0.0.0.0:50052', grpc.ServerCredentials.createInsecure());
server.start();
}

main();
`

Client side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const grpc_promise = require('grpc-promise');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

grpc_promise.promisifyAll(client);

client.testSimpleStream()
.sendMessage({id: 1})
.then(res => {
console.log('Client: Stream Message Received = ', res); // Client: Stream Message Received = [{id: 1},{id: 1}]
})
.catch(err => console.error(err))
;
}

main();
`

$3

Implementation of TestStreamStream message

IMPORTANT: In order to keep track of the messages sent and to be able to callback all the requests,
the server implementation needs to answer with the same id received

Server side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

const testStreamStream = function (call) {
call.on('data', function (message) {
console.log('Server: Stream Message Received = ', message); // Server: Stream Message Received = {id: 1}
setTimeout(function () {
call.write({
id: message.id // IMPORTANT only for Bidirectional Stream Request
});
}, 10);
});

call.on('end', function () {
call.end();
});
};

main = function () {
server = new grpc.Server();
server.addService(test_proto.Test.service, {
testStreamStream: testStreamStream
});

server.bind('0.0.0.0:50052', grpc.ServerCredentials.createInsecure());
server.start();
}

main();
`

Client side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const grpc_promise = require('grpc-promise');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

// Optional timeout_message out definition (defaults = 50)
// for the response of a single message of a bidirectional stream function in grpc.
// Don't confuse with timeout parameter used to set a deadline to the open connection.
grpc_promise.promisifyAll(client, { timeout_message: 100 });

t = client.testStreamStream();
t.sendMessage({})
.then(res => {
console.log('Client: Stream Message Received = ', res); // Client: Stream Message Received = {id: 0}
})
.catch(err => console.error(err))
;
t.sendMessage({})
.then(res => {
console.log('Client: Stream Message Received = ', res); // Client: Stream Message Received = {id: 1}
})
.catch(err => console.error(err))
;
t.end();
}

main();
`

$3

Client side:

`js
const grpc = require('grpc');
const protoLoader = require('@grpc/proto-loader');
const grpc_promise = require('grpc-promise');

const packageDefinition = protoLoader.loadSync(
__dirname + '/protobuf/test.proto',
{
keepCase: true,
longs: String,
enums: String,
defaults: true,
oneofs: true
}
);

const protoDescriptor = grpc.loadPackageDefinition(packageDefinition);
const test_proto = protoDescriptor.test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

const meta = new grpc.Metadata();
meta.add('key', 'value');

grpc_promise.promisifyAll(client, {metadata: meta});

client.testSimpleSimple()
.sendMessage({id: 1})
.then(res => {
console.log('Client: Simple Message Received = ', res) // Client: Simple Message Received = {id: 1}
})
.catch(err => console.error(err))
;
}

main();
`

$3

The deadline parameter is used to to set a timestamp in millisenconds for the entire call to complete.
For architectural reasons and knowing that the original deadline is passed as a timestamp,
grpc-module forces to set a timeout parameter in milliseconds.
It means the number of milliseconds we want to wait as most for the response:

`js
// We give a deadline of 1 second (= 1000ms)
grpc_promise.promisifyAll(client, { timeout: 1000 });
`

$3

Client side:

`js
const grpc = require('grpc');
const grpc_promise = require('grpc-promise');
const test_proto = grpc.load(__dirname + '/protobuf/test.proto').test;

function main() {
const client = new test_proto.Test('localhost:50052', grpc.credentials.createInsecure());

const meta = new grpc.Metadata();
meta.add('key', 'value');

grpc_promise.promisify(client, ['testSimpleSimple'] {metadata: meta});

client.testSimpleSimple()
.sendMessage({id: 1})
.then(res => {
console.log('Client: Simple Message Received = ', res) // Client: Simple Message Received = {id: 1}
})
.catch(err => console.error(err))
;
}

main();
``

MIT License

Copyright (c) 2017 Carles Sistare

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.