Wsrtjtyk

I am currently working on dockerizing a tested socket.io app for a simple chat application, using socket.io, and mocha for testing. the server opens up a socket for listening on port 3000 and the test client uses the socket to emit messages or receive emissions.

I am using version 3 of docker compose files.

nodeserver dockerfile:

FROM node:10



WORKDIR /usr/src/appserver



COPY package*.json ./

COPY public public

COPY main.js main.js



RUN npm install

RUN npm install express

RUN npm install socket.io



CMD ["npm", "start"]

test dockerfile:

FROM nodeserver



COPY test test



RUN npm update && 

    npm install -g mocha && 

    npm install -g socket.io-client



CMD ["npm", "test"]

docker-compose:

version: "3"



services:

 nodeserver:

   build: .

   expose:

      - "3000"

   image: ws



 test:

   depends_on:

      - nodeserver

   links:

     - nodeserver

   build: ./test

   image: test_image

my node server is listening on port 3000, and on connection sends a hi message to all.

let express = require('express');

let app = express();

let http = require('http').createServer(app);

let io = require('socket.io')(http);

http.listen(3000, function ()

{

    console.log('listening on *:3000');

});



io.on('connection', function(socket)

{

    console.log('a user connected');



    io.emit('hi', 'hi');

});

and my mocha test looks like this, which in essence attaches itself as a client and waits for the the hi message to come.

const url = 'ws://nodeserver:3000';





describe("Chat Server", function()

{

    it("Should broadcast hi!", function(done)

    {

        let client1 = io.connect(url, options);



        client1.on('connect', function()

        {

            client1.on('hi', function(msg)

            {

                msg.should.equal("hi");

                client1.disconnect();

                done();

            });

        });

    });

}

running docker-compose, runs the nodeserver and the test client fails with timeout, which tells me the client cannot see the swarm network.

now running the dockers separately, that is exposing nodeservers to host and trying to connect to my localhost instead works perfectly and the test passes. This tells me that my socket and the way I communicate with nodeserver should be correct, which would basically mean that I should be having a problem with setting up my swarm's network. Can somebody tell me what I am doing wrong here?

I think your configuration looks good, it's a matter of readiness of your nodeserver. Even with depends_on, there is no guarantee that nodeserver is ready when test starts. (also links is useless and deprecated).

To verify my hypothesis, try the following sequence:

docker-compose up -d nodeserver

wait a few seconds

docker-compose up -d test

ok so apparently I was running the test on top of nodeserver was not a good idea. I think the keyword here is

depends_on:

  - nodeserver

in the "test" service part of compose. This forces test service to build the server again and run the command

CMD ["npm", "start"]

from "nodeserver" service, and that screws things up, after removing the "depends_on", all my tests pass and two containers can connect.

the complete bare bone project can be found here

https://github.com/tetrohed/couch