How to connect to postgres inside docker compose with NodeJs? - node.js

Question

I have installed Mainflux in Cloud Server using Docker. Postgres DB is also
running in Docker Container. I have a situation to connect to PostgresDB with Node.Js(programmatically). I found "pg" module to connect to Cloud
Postgres DB. But, am unable to connect to Postgres which is running on
Docker Container. I pasted my code below, pls let me know the scenario to connect "Docker Postgres".
const pg = require('pg');
const conStringPri = postgres://mainflux:mainflux#MYIP/mainflux-things-db;
const Client = pg.Client;
const client = new Client({connectionString: conStringPri});
client.connect();
client.query(CREATE DATABASE DB_Name)
.then(() => client.end());
Getting error as below:
node:8084) UnhandledPromiseRejectionWarning: Error: connect ECONNREFUSED
MYIP:5432
at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1191:14)
(node:8084) UnhandledPromiseRejectionWarning: Unhandled promise rejection.
This error originated either by throwing inside of an async function
without a catch block or by rejecting a promise which was not handled with
.catch() (rejection id: 1)
(node:8084) [DEP0018] DeprecationWarning: Unhandled promise rejections are
deprecated. In the future, promise rejections that are not handled will
terminate the Node.js process with a
non-zero exit code.
(node:8084) UnhandledPromiseRejectionWarning: Error: Connection
terminated unexpectedly
at Connection.con.once
(D:\postgres_Nodejs\node_modules\pg\lib\client.js:200:9)
at Object.onceWrapper (events.js:313:30)
at emitNone (events.js:106:13)
at Connection.emit (events.js:208:7)
at Socket.
(D:\postgres_Nodejs\node_modules\pg\lib\connection.js:76:10)
at emitOne (events.js:116:13)
at Socket.emit (events.js:211:7)
at TCP._handle.close [as _onclose] (net.js:561:12)

Answer 1

If you started Mainflux by using docker-compose configuration supplied here https://github.com/mainflux/mainflux/blob/master/docker/docker-compose.yml , then your PostgreSQL container doesn't have the port exposed to the host. In order to be able to connect to the database, you need to expose this port.
Here's an example of how the part of the docker-compose would look, with the things-db container having port 5432 (default PostgreSQL port) exposed
things-db:
image: postgres:10.2-alpine
container_name: mainflux-things-db
restart: on-failure
environment:
POSTGRES_USER: mainflux
POSTGRES_PASSWORD: mainflux
POSTGRES_DB: things
networks:
- mainflux-base-net
ports:
- 5432:5432
So you will need to modify your docker-compose.yml.
Please note that the Mainflux docker compose has 2 PostgreSQL databases in 2 containers: things-db and users-db.