greeter_client.js

/*
This is an alternate version of the example client in
https://github.com/grpc/grpc/blob/master/examples/node/dynamic_codegen/greeter_client.js
that reproduces issue #15933.

Repro steps:

$ cd grpc/examples/node/dynamic_codegen
$ npm install

$ npm install grpc@1.11.3
$ node greeter_server.js &
$ node greeter_client.js  # note no errors occur on 1.11.3

$ npm install grpc@1.12.1
$ node greeter_client.js  # note "Failed to create subchannel" errors
*/


var PROTO_PATH = __dirname + '/../../protos/helloworld.proto';

var grpc = require('grpc');
var hello_proto = grpc.load(PROTO_PATH).helloworld;

var readline = require('readline');
var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal: false
});

function newClient() {
    return new hello_proto.Greeter(
        'localhost:50051',  // greeter_server.js must already be running
        grpc.credentials.createInsecure(),
        {'grpc.lb_policy_name': 'round_robin'},  // Removing this line eliminates the issue!
    );
}


function main() {
    let client, numResponses = 0, numRequests = 0;
    function newRequest(makeClient) {
        if (makeClient) {
          client = newClient();
        }
        numRequests++;
        client.sayHello({name: numRequests.toString()}, function(err, resp) {
            numResponses++;
            if (err) {
                console.log(`Error: ${err.message}`);
            } else {
                console.log(`Response ${resp.message}`);
            }
        });
        console.log(`Request ${numRequests}`);
    }
    newRequest(true);
    rl.on('line', function(line){
        const makeClient = line.startsWith('n');
        newRequest(makeClient);
    });
}

main();