错误：点击 Docker 容器化 Node.js 应用程序端点时连接 ECONNREFUSED 0.0.0.0:8000

Question

I'm just starting with Docker and dough I succeed in creating an image and a container from it I'm not succeeding in connecting to the container's port with postman and I get Error: connect ECONNREFUSED 0.0.0.0:8000 .

In my server.js file I have:

const app = require('./api/src/app');

const port = process.env.PORT || 3000; // PORT is set to 5000

app.listen(port, () => {
  console.log('App executing to port ', port);
});

in my index.js I have:

const express = require('express');

 const router = express.Router();
 
 router.get('/api', (req, res) => {
   res.status(200).send({
     success: 'true',
     message: 'Welcome to fixit',
     version: '1.0.0',
   });
 });
 
 module.exports = router;

so if I run my app with either npm start or nodemon server.js the localhost:3000/api endpoint works as expected.

I then build a docker image for my app with the command docker build. -t fixit-server docker build. -t fixit-server with this Dockerfile :

FROM node:15.14.0

# Create app directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package.json package.json
COPY package-lock.json package-lock.json

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production

# Bundle app source
COPY . .

EXPOSE 5000

# CMD ["npm", "start"]
CMD npm start
# CMD ["nodemon", "server.js"]

and run the container with the command docker run -d -p 8000:5000 --name fixit-container fixit-server tail -f /dev/null

and listing the containers with docker ps -a shows it running:

CONTAINER ID   IMAGE          COMMAND                  CREATED         STATUS         PORTS                    NAMES
da0e4ef12402   fixit-server   "docker-entrypoint.s…"   9 seconds ago   Up 8 seconds   0.0.0.0:8000->5000/tcp   fixit-container

but when I hit the endpoint 0.0.0.0:8000/api I get the ECONNREFUSED error. I tried both CMD ["npm", "start"] and CMD npm start but I get the error both ways. Can you what I'm doing wrong?

Answer 1

Update:

@Vincenzo was using docker-machine and to be able to check whether the app was working properly, we needed to execute the following command in the terminal:

docker-machine env

The result was:

export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://192.168.99.102:2376"
export DOCKER_CERT_PATH="/Users/vinnytwice/.docker/machine/machines/default"
export DOCKER_MACHINE_NAME="default"

Then based on the DOCKER_HOST value, we hit 192.168.99.102:8000/api and it was working.

---

I believe the problem is you're never setting the PORT environment variable to 5000 .

EXPOSE docker command is a no op. Meaning that it will do nothing but is only for the developer to know that you're exposing the port 5000. You can read it in Docker documentation .

You need to either set an environment variable or pass an environment variable at runtime to the container to specifically tell it that PORT is 5000.

Method 1:

You can change your Dockerfile like below:

FROM node:15.14.0

# Create app directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package.json package.json
COPY package-lock.json package-lock.json

RUN npm install
# If you are building your code for production
# RUN npm ci --only=production

# Bundle app source
COPY . .

ENV PORT=5000

EXPOSE $PORT

# CMD ["npm", "start"]
CMD npm start
# CMD ["nodemon", "server.js"]

Method 2:

Simply use the following command to run your container:

docker run -d -p 8000:5000 --name fixit-container --env PORT=5000 fixit-server