Running in Docker/Kubernetes

[domderen]

Hi,

I'm wondering if you might have some examples of how to use this library inside Docker/Kubernetes environment? I running into issues when trying to set it up in such an environment.

I tried running the container with such parameters:

index.js

const mdnsService = require('multicast-dns')

const port = process.env.PORT || 53

const server = mdnsService({
  port
})

server.on('query', function (query) {
  console.log('DNS Query:', query.questions)
})

console.log(`Box up & running on port ${port}.`);

['SIGHUP', 'SIGINT', 'SIGQUIT', 'SIGILL', 'SIGTRAP', 'SIGABRT',
    'SIGBUS', 'SIGFPE', 'SIGUSR1', 'SIGSEGV', 'SIGUSR2', 'SIGTERM'
].forEach(function (sig) {
    process.on(sig, function () {
      console.log('Box is shutting down.')
      server.destroy()
    })
})

Dockerfile

FROM node:current-alpine3.13
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

# update and install dependency
RUN apk update && apk upgrade
RUN apk add git

# copy the app, note .dockerignore
COPY package*.json /usr/src/app/
RUN npm install

COPY . /usr/src/app/

CMD [ "node", "index.js" ]

Commands to build & run the container:

docker build -t multicast-dns .
docker run -it -e PORT=53 -p 53:53/udp -p 53:53/tcp multicast-dns

Command to test the app:

dig @127.0.0.1 +tries=1 +time=1 some.domain.name.com

The above command works fine when I run this app via node index.js and I can see the log statement for the DNS query. But when I run it in docker, it looks like my diq requests are not coming through.

Thanks in advance for your help!

[johnwoo-nl]

mDNS uses UDP port 5353, not port 53 like regular DNS. See: https://datatracker.ietf.org/doc/html/rfc6762#appendix-A
So I'm kind of surprised that you mention it does work when run outside of a docker container.

[slavaGanzin]

@johnwoo-nl Systemd-resolved will pickup anything from 5353
https://wiki.archlinux.org/title/Systemd-resolved#mDNS

and I assume this behavior is mirrored on other OSes