Docker two tier application issue: failed to connect to mongo container - docker

Question

I have a simple nodeJS application consisting of the frontend and a mongo database. I want to deploy it via Docker.
In my docker-compose file I have the following:
version: '2'
services:
express-container:
build: .
ports:
- "3000:3000"
depends_on:
- mongo-container
mongo-container:
image: mongo:3.0
When I run docker-compose up, I have the following error:
Creating todoangularv2_mongo-container_1 ...
Creating todoangularv2_mongo-container_1 ... done
Creating todoangularv2_express-container_1 ...
Creating todoangularv2_express-container_1 ... done
Attaching to todoangularv2_mongo-container_1, todoangularv2_express-container_1
mongo-container_1 | 2017-07-25T15:26:09.863+0000 I CONTROL [initandlisten] MongoDB starting : pid=1 port=27017 dbpath=/data/db 64-bit host=25f03f51322b
mongo-container_1 | 2017-07-25T15:26:09.864+0000 I CONTROL [initandlisten] db version v3.0.15
mongo-container_1 | 2017-07-25T15:26:09.864+0000 I CONTROL [initandlisten] git version: b8ff507269c382bc100fc52f75f48d54cd42ec3b
mongo-container_1 | 2017-07-25T15:26:09.864+0000 I CONTROL [initandlisten] build info: Linux ip-10-166-66-3 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 BOOST_LIB_VERSION=1_49
mongo-container_1 | 2017-07-25T15:26:09.864+0000 I CONTROL [initandlisten] allocator: tcmalloc
mongo-container_1 | 2017-07-25T15:26:09.864+0000 I CONTROL [initandlisten] options: {}
mongo-container_1 | 2017-07-25T15:26:09.923+0000 I JOURNAL [initandlisten] journal dir=/data/db/journal
mongo-container_1 | 2017-07-25T15:26:09.924+0000 I JOURNAL [initandlisten] recover : no journal files present, no recovery needed
express-container_1 | Listening on port 3000
express-container_1 |
express-container_1 | events.js:72
express-container_1 | throw er; // Unhandled 'error' event
express-container_1 | ^
express-container_1 | Error: failed to connect to [mongo-container:27017]
So my frontend cannot reach the mongo container called 'mongo-container' in the docker-compose file. In the application itself I'm giving the URL for the mongo database as follows:
module.exports = {
url : 'mongodb://mongo-container:27017/todo'
}
Any idea how I can change my application so that when it is run on Docker, I don't have this connectivity issue?
EDIT: the mongo container gives the following output:
WAUTERW-M-T3ZT:vagrant wim$ docker logs f63
2017-07-26T09:15:02.824+0000 I CONTROL [initandlisten] MongoDB starting : pid=1 port=27017 dbpath=/data/db 64-bit host=f637f963c87f
2017-07-26T09:15:02.825+0000 I CONTROL [initandlisten] db version v3.0.15
2017-07-26T09:15:02.825+0000 I CONTROL [initandlisten] git version: b8ff507269c382bc100fc52f75f48d54cd42ec3b
...
2017-07-26T09:15:21.461+0000 I STORAGE [FileAllocator] done allocating datafile /data/db/local.0, size: 64MB, took 0.024 secs
2017-07-26T09:15:21.476+0000 I NETWORK [initandlisten] waiting for connections on port 27017
The express container gives the following output:
WAUTERW-M-T3ZT:vagrant wim$ docker logs 25a
Listening on port 3000
events.js:72
throw er; // Unhandled 'error' event
^
Error: failed to connect to [mongo-container:27017]
at null.<anonymous> (/usr/src/app/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:555:74)
at EventEmitter.emit (events.js:106:17)
at null.<anonymous> (/usr/src/app/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection_pool.js:156:15)
at EventEmitter.emit (events.js:98:17)
at Socket.<anonymous> (/usr/src/app/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection.js:534:10)
at Socket.EventEmitter.emit (events.js:95:17)
at net.js:441:14
at process._tickCallback (node.js:415:13)
EDIT: the issue appeared in the Dockerfile. Here is a corrected one (simplified a bit as I started from a node image rather than an Ubuntu image):
FROM node:0.10.40
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY . /usr/src/app
RUN npm install
CMD ["node", "/usr/src/app/bin/www"]

Answer 1

You could substitute depends_on by links session, that express dependency between services like depends_on and, according to the documentation, containers for the linked service will be reachable at a hostname identical to the alias, or the service name if no alias was specified.
version: '2'
services:
express-container:
build: .
ports:
- "3000:3000"
links:
- "mongo-container"
mongo-container:
image: mongo:3.0

Answer 2

The issue appeared in the Dockerfile. Here is a corrected one (simplified a bit as I started from a node image rather than an Ubuntu image):
FROM node:0.10.40
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app
COPY . /usr/src/app
RUN npm install
CMD ["node", "/usr/src/app/bin/www"]