Failed to connect to a mongodb docker container from mongoose on host - mongodb

Question

I'm trying to connect to mongodb running in docker from the app running on host using mongoose but it failed.
I can't use the port 27017 for the new mongodb container because it is used by other container. So I followed the guide here for setting it up using the compose.
Below are the snippets:
docker-compose.yml
version: '3'
services:
db:
image: mongo:latest
restart: always
ports:
- '8081:8081'
environment:
MONGO_INITDB_ROOT_USERNAME: root1
MONGO_INITDB_ROOT_PASSWORD: password1
But when I do docker-ps, port 27017 still there but I'm not sure if that causes an issue.
PORTS
0.0.0.0:8081->8081/tcp, 27017/tcp
Then I created a new user in admin database.
use admin
db.createUser(
{
user: "admin1",
pwd: "password2",
roles: [ { role: "userAdminAnyDatabase", db: "admin" }, "readWriteAnyDatabase" ]
}
)
server.js
const connectOption = {
useNewUrlParser: true,
user: 'admin1',
pass: 'password2',
authSource: 'admin',
}
const mongoURL = 'mongodb://localhost:8081/app1';
mongoose.connect(mongoURL, connectOption)
.then(() => console.log('MongoDB Connected'))
.catch(error => console.log(error));
And the error I received is
{
MongoNetworkError: failed to connect to server [localhost:8081] on first connect [MongoNetworkError: write EPIPE]
...
...
...
name: 'MongoNetworkError',
errorLabels: [ 'TransientTransactionError' ],
[Symbol(mongoErrorContextSymbol)]: {}
}

Answer 1

Assuming you're running nodejs application as a docker-compose service, in db service remove ports section (including - '8081:8081'
line). In server.js, change const mongoURL = 'mongodb://localhost:8081/app1'; to const mongoURL = 'mongodb://db:27017/app1';.
If you want to access the db from host machine, change ports 8081:8081 to <give-a-port-number>:27017.