NodeJS is not able to access postgres database

Question

My app.js file is as follows

var express = require('express');
var app = express();
var uuid = require('node-uuid');

var pg = require('pg');
var conString = process.env.DB; // "postgres://username:password@localhost/database";

// Routes
app.get('/api/status', function(req, res) {
  pg.connect(conString, function(err, client, done) {
    if(err) {
      return res.status(500).send('error fetching client from pool');
    }
    client.query('SELECT now() as time', [], function(err, result) {
      //call `done()` to release the client back to the pool
      done();

      if(err) {
        return res.status(500).send('error running query');
      }

      return res.json({
        request_uuid: uuid.v4(),
        time: result.rows[0].time
      });
    });
  });
});

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.json({
      message: err.message,
      error: err
    });
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.json({
    message: err.message,
    error: {}
  });
});


module.exports = app;

and my Dockerfile is as follows

FROM node:14

WORKDIR /app

COPY package*.json ./

RUN  npm install

COPY . .

my docker-compose file is as follows:

version: "3.2"
services:
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: test123
      POSTGRES_DB: testing
    volumes:
      - ./pgdata:/var/lib/postgresql/data
  web:
    build: .
    command: npm start app.js
    depends_on:
      - db
    environment:
      DB: 'postgres://postgres:test123@localhost:5432/testing'
    ports:
      - "3000:3000"

When I am checking into the container DB, I can see the user, database but my app.js file cannot fetch a value from the database. I am routing the data in this endpoint /api/status when I am accessing http://ip-address:3000 == then i am getting 404 error which I mentioned in my code. without docker, I can easily access my output at the given endpoint.

Any help will be helpful. Thanksss

Which IP url do you call on `http://ip-address:3000` the IP of the container? Try with `http://localhost:3000` but stop the local one if is active. — Max, Aug 27 '21 at 10:29
ip-address of my localmachine, my container running on different IP maybe I should try this ``postgres://postgres:test123@host.docker.internal:5432/testing`` — Sakar Mehra, Aug 27 '21 at 10:34
The express apps I've seen have all had an `app.listen` call. Where do you tell your app to listen on port 3000? — Hans Kilian, Aug 27 '21 at 11:15
This will not help with 404 error, but your front will not be able to connect to your database. Change your database connection from `DB: 'postgres://postgres:test123@localhost:5432/testing'` to `DB: 'postgres://postgres:test123@db:5432/testing'` As you are running docker containers, localhost refers to the container itself, not your host. You need to connecto to another container. Also add a ports section in `db` service to expose 5432 port — usuario, Aug 27 '21 at 13:16
@usuario I already tried those things, it doesn't seems to be working — Sakar Mehra, Aug 27 '21 at 13:17
Please trim your code to make it easier to find your problem. Follow these guidelines to create a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example). — Community, Aug 28 '21 at 01:23

score 1 · Answer 1 · answered Aug 27 '21 at 10:54

When you ask docker-compose to spin up your containers, it creates a virtual network where each container has it's own ip address. When you - in your web container - ask to connect to localhost, you're trying to connect to the web container itself and not the database container.

You can access the database container by its service name db. So change your docker-compose file from

environment:
  DB: 'postgres://postgres:test123@localhost:5432/testing'

to

environment:
  DB: 'postgres://postgres:test123@db:5432/testing'

NodeJS is not able to access postgres database

1 Answers1