hawkly-grpc

hawkly gRPC wrapper for javascript

Repository | npm

Work in progress

This is a wrapper around gRPC to add opentracing and async/await.

Usage

Server

To run the server, add the hawklyMiddleware with configuration as a middleware to Mali.

  const PROTO_PATH: string = __dirname + '/../proto/helloworld.proto';

  const grpcHost = '0.0.0.0:1000';
  const app: Mali = new Mali(PROTO_PATH);

  const hawklyTracerOptions: any = {
    accessToken: 'test',
    componentName: 'testServerComponent',
  };


  app.use(hawklyMiddleware(hawklyTracerOptions));

  app.use({
    sayHello: () => {
      // handler code
    }
  });
  app.start(grpcHost);

Client

We provide a wrapper for the grpc client (based on a rewrite of https://www.npmjs.com/package/grpc-caller), which will automatically create a span and add it's context to the outgoing grpc call.

To create a client you need to pass options to instantiate both the Hawkly Tracer and the grpc client.

import {
  // Use this to create a new gRPC client from a proto file
  // This lets you call the services defined in the proto file
  createClient,
} from 'hawkly-grpc';

// defince your proto path
const PROTO_PATH: string = __dirname + '/helloworld.proto';

// create the client and tracer
const { tracer, client } = createClient(
  {
    // hawkly
    accessToken: 'get your token from hawkly.io',
    componentName: 'myComponent',
    // grpc
    host: grpcHost,
    proto: PROTO_PATH,
    name: 'Greeter',
  },
);

  // Create a new span to cover this unit of work
  const span: any = tracer.startSpan('myFirstSpan');

  // await the result of our gRPC call to `sayHello`
  // and an object of options to the call to specify the arg etc
  const request:Promise<any> = await client.sayHello({
    arg: { name: grpcHost },
    // pass the span we just created
    span,
  });

  // do stuff with result

  // finish our span
  span.finish();

Get the request Span

If you need access to the Span created for the request, you can pass in requestSpan:true to the options of the call. This will return you a tuple with request as a Promise and requestSpan and span as the span (both exist so you can use destructuring without having a local variable conflict with span).

import {
  // Use this to create a new gRPC client from a proto file
  // This lets you call the services defined in the proto file
  createClient,
  // request interface type
  TracedUnaryRequest,
} from 'hawkly-grpc';

  // await the result of our gRPC call to `sayHello`
  // and an object of options to the call to specify the arg etc
  const {request, requestSpan}:TracedUnaryRequest = await client.sayHello({
    arg: { name: grpcHost },
    // pass the span we just created
    span,
    requestSpan: true,
  });
  const result:any = await request;

Errors

To simplify error handling for errors raised specifically in the server handler code we export an error type HawklyError.

When you throw it in your rpc handler it will be returned to the caller and instatiated as a HawklyError on the caller side.

   function sayHello() {
      throw new HawklyError('This is a test error', 'testError', { foo: 'bar' });
    }

      try {
        const result: any = await client.sayHello({
          arg: { name: grpcHost },
          // pass in our span
          span,
        });
        // do something with result
      } catch (error) {
        if(error instanceof HawklyError){
          // error throw by server rpc
          console.log(error.getMessage());   // 'This is a test error'
          console.log(error.getEventName()); //'testError'
          console.log(error.getPayload());   //{ foo: 'bar' }
        } else {
          // any other grpc error
        }
      }

More information

http://www.grpc.io/

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hawkly.io Owen Kelly