A JavaScript implementation of gRPC for browser clients. For more information, including a quick start, see the gRPC-web documentation.
gRPC-web clients connect to gRPC services via a special proxy; by default, gRPC-web uses Envoy.
In the future, we expect gRPC-web to be supported in language-specific web frameworks for languages such as Python, Java, and Node. For details, see the roadmap.
Eager to get started? Try the Hello World example. From this example, you'll learn how to do the following:
- Define your service using protocol buffers
- Implement a simple gRPC Service using NodeJS
- Configure the Envoy proxy
- Generate protobuf message classes and client service stub for the client
- Compile all the JS dependencies into a static library that can be consumed by the browser easily
You can also try to run a more advanced Echo app from the browser with a streaming example.
From the repo root directory:
$ docker-compose pull prereqs node-server envoy commonjs-client
$ docker-compose up node-server envoy commonjs-client
Open a browser tab, and visit http://localhost:8081/echotest.html.
To shutdown: docker-compose down
.
The gRPC-web runtime library is available at npm
:
$ npm i grpc-web
You can download the protoc-gen-grpc-web
protoc plugin from our
release page:
If you don't already have protoc
installed, you will have to download it
first from here.
Make sure they are both executable and are discoverable from your PATH.
For example, in MacOS, you can do:
$ sudo mv ~/Downloads/protoc-gen-grpc-web-1.3.1-darwin-x86_64 \
/usr/local/bin/protoc-gen-grpc-web
$ chmod +x /usr/local/bin/protoc-gen-grpc-web
Typically, you will run the following command to generate the proto messages
and the service client stub from your .proto
definitions:
$ protoc -I=$DIR echo.proto \
--js_out=import_style=commonjs:$OUT_DIR \
--grpc-web_out=import_style=commonjs,mode=grpcwebtext:$OUT_DIR
You can then use Browserify, Webpack, Closure Compiler, etc. to resolve imports at compile time.
import_style=closure
: The default generated code has
Closure goog.require()
import style.
import_style=commonjs
: The
CommonJS style require()
is
also supported.
import_style=commonjs+dts
: (Experimental) In addition to above, a .d.ts
typings file will also be generated for the protobuf messages and service stub.
import_style=typescript
: (Experimental) The service stub will be generated
in TypeScript. See TypeScript Support below for information on how to
generate TypeScript files.
Note: The commonjs+dts
and typescript
styles are only supported by
--grpc-web_out=import_style=...
, not by --js_out=import_style=...
.
For more information about the gRPC-web wire format, see the specification.
mode=grpcwebtext
: The default generated code sends the payload in the
grpc-web-text
format.
Content-type: application/grpc-web-text
- Payload are base64-encoded.
- Both unary and server streaming calls are supported.
mode=grpcweb
: A binary protobuf format is also supported.
Content-type: application/grpc-web+proto
- Payload are in the binary protobuf format.
- Only unary calls are supported for now.
Let's take a look at how gRPC-web works with a simple example. You can find out how to build, run and explore the example yourself in Build and Run the Echo Example.
The first step when creating any gRPC service is to define it. Like all gRPC services, gRPC-web uses protocol buffers to define its RPC service methods and their message request and response types.
message EchoRequest {
string message = 1;
}
...
service EchoService {
rpc Echo(EchoRequest) returns (EchoResponse);
rpc ServerStreamingEcho(ServerStreamingEchoRequest)
returns (stream ServerStreamingEchoResponse);
}
Next you need to have a gRPC server that implements the service interface and a gateway proxy that allows the client to connect to the server. Our example builds a simple Node gRPC backend server and the Envoy proxy.
For the Echo service: see the service implementations.
For the Envoy proxy: see the config yaml file.
Once the server and gateway are up and running, you can start making gRPC calls from the browser!
Create your client:
var echoService = new proto.mypackage.EchoServiceClient(
'http://localhost:8080');
Make a unary RPC call:
var request = new proto.mypackage.EchoRequest();
request.setMessage(msg);
var metadata = {'custom-header-1': 'value1'};
echoService.echo(request, metadata, function(err, response) {
if (err) {
console.log(err.code);
console.log(err.message);
} else {
console.log(response.getMessage());
}
});
Server-side streaming is supported!
var stream = echoService.serverStreamingEcho(streamRequest, metadata);
stream.on('data', function(response) {
console.log(response.getMessage());
});
stream.on('status', function(status) {
console.log(status.code);
console.log(status.details);
console.log(status.metadata);
});
stream.on('end', function(end) {
// stream end signal
});
// to close the stream
stream.cancel()
For an in-depth tutorial, see this page.
You can set a deadline for your RPC by setting a deadline
header. The value
should be a Unix timestamp, in milliseconds.
var deadline = new Date();
deadline.setSeconds(deadline.getSeconds() + 1);
client.sayHelloAfterDelay(request, {deadline: deadline.getTime()},
(err, response) => {
// err will be populated if the RPC exceeds the deadline
...
});
The grpc-web
module can now be imported as a TypeScript module. This is
currently an experimental feature. Any feedback welcome!
When using the protoc-gen-grpc-web
protoc plugin, mentioned above, pass in
either:
import_style=commonjs+dts
: existing CommonJS style stub +.d.ts
typingsimport_style=typescript
: full TypeScript output
Do not use import_style=typescript
for --js_out
, it will silently be
ignored. Instead you should use --js_out=import_style=commonjs
, or
--js_out=import_style=commonjs,binary
if you are using mode=grpcweb
. The
--js_out
plugin will generate JavaScript code (echo_pb.js
), and the
-grpc-web_out
plugin will generate a TypeScript definition file for it
(echo_pb.d.ts
). This is a temporary hack until the --js_out
supports
TypeScript itself.
For example, this is the command you should use to generate TypeScript code using the binary wire format
$ protoc -I=$DIR echo.proto \
--js_out=import_style=commonjs,binary:$OUT_DIR \
--grpc-web_out=import_style=typescript,mode=grpcweb:$OUT_DIR
It will generate the following files:
echo_grpc_web_pb.ts
- Generated by--grpc-web_out
, contains the TypeScript gRPC-web code.echo_pb.js
- Generated by--js_out
, contains the JavaScript Protobuf code.echo_pb.d.ts
- Generated by--grpc-web_out
, contains TypeScript definitions forecho_pb.js
.
import * as grpcWeb from 'grpc-web';
import {EchoServiceClient} from './echo_grpc_web_pb';
import {EchoRequest, EchoResponse} from './echo_pb';
const echoService = new EchoServiceClient('http://localhost:8080', null, null);
const request = new EchoRequest();
request.setMessage('Hello World!');
const call = echoService.echo(request, {'custom-header-1': 'value1'},
(err: grpcWeb.RpcError, response: EchoResponse) => {
console.log(response.getMessage());
});
call.on('status', (status: grpcWeb.Status) => {
// ...
});
For the full TypeScript example, see ts-example/client.ts.
Multiple proxies support the gRPC-web protocol.
-
The current default proxy is Envoy, which supports gRPC-web out of the box.
$ docker-compose up -d node-server envoy commonjs-client
-
You can also try the gRPC-web Go proxy.
$ docker-compose up -d node-server grpcwebproxy binary-client
-
Apache APISIX has also added grpc-web support, and more details can be found here.