Docker-compose: node_modules not present in a volume after npm install succeeds

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I have an app with the following services:

  • web/ – holds and runs a python 3 flask web server on port 5000. Uses sqlite3.
  • worker/ – has an index.js file which is a worker for a queue. the web server interacts with this queue using a json API over port 9730. The worker uses redis for storage. The worker also stores data locally in the folder worker/images/

Now this question only concerns the worker.

worker/Dockerfile

FROM node:0.12

WORKDIR /worker

COPY package.json /worker/
RUN npm install

COPY . /worker/

docker-compose.yml

redis:
    image: redis
worker:
    build: ./worker
    command: npm start
    ports:
        - "9730:9730"
    volumes:
        - worker/:/worker/
    links:
        - redis

When I run docker-compose build, everything works as expected and all npm modules are installed in /worker/node_modules as I’d expect.

npm WARN package.json [email protected] No README data

> [email protected] install /worker/node_modules/pageres/node_modules/screenshot-stream/node_modules/phantom-bridge/node_modules/phantomjs
> node install.js

<snip>

But when I do docker-compose up, I see this error:

worker_1 | Error: Cannot find module 'async'
worker_1 |     at Function.Module._resolveFilename (module.js:336:15)
worker_1 |     at Function.Module._load (module.js:278:25)
worker_1 |     at Module.require (module.js:365:17)
worker_1 |     at require (module.js:384:17)
worker_1 |     at Object.<anonymous> (/worker/index.js:1:75)
worker_1 |     at Module._compile (module.js:460:26)
worker_1 |     at Object.Module._extensions..js (module.js:478:10)
worker_1 |     at Module.load (module.js:355:32)
worker_1 |     at Function.Module._load (module.js:310:12)
worker_1 |     at Function.Module.runMain (module.js:501:10)

Turns out none of the modules are present in /worker/node_modules (on host or in the container).

If on the host, I npm install, then everything works just fine. But I don’t want to do that. I want the container to handle dependencies.

What’s going wrong here?

(Needless to say, all packages are in package.json.)

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