Run a ruby script in a docker container which connects to mongodb localhost port

Question

I am a newbie with docker and trying my hands onto it. I am facing a minor problem, your help in any way would be appreciated!

I have a ruby script in which I am connecting to my localhost port which is assigned to my mongodb database. I am using MongoClient to connect to the database from the script:

clientDB = Mongo::Client.new(["localhost:37017"], :database => 'Database', :user => 'user', :password => 'password')

or

clientDB = Mongo::Client.new(["127.0.0.1:37017"], :database => 'Database', :user => 'user', :password => 'password')

If I run the script using ruby monthly_count_script.rb command, it works perfectly but as I am exploring Docker, I want to run that script into a container. So to run a container I am using following command

docker run -it --rm --name my-running-script -v "$PWD":/usr/src/app -v "$PWD"/../gems:/usr/local/bundle -w /usr/src/app --net=host ruby ruby monthly_count_script.rb

Unfortunately I am keep getting following error and I don't know why it is not able to connect to the localhost 37017 port even though my database is working properly and I am able to connect to the database using Robomongo or mongodb console.

This is the error log:

D, [2018-06-04T14:15:11.527381 #1] DEBUG -- : MONGODB | Topology type 'single' initializing.
D, [2018-06-04T14:15:11.527639 #1] DEBUG -- : MONGODB | Server 127.0.0.1:37017 initializing.
D, [2018-06-04T14:15:11.529252 #1] DEBUG -- : MONGODB | Connection refused - connect(2) for 127.0.0.1:37017
D, [2018-06-04T14:15:11.530774 #1] DEBUG -- : MONGODB | Topology type 'single' initializing.
D, [2018-06-04T14:15:11.531058 #1] DEBUG -- : MONGODB | Server 127.0.0.1:37017 initializing.
D, [2018-06-04T14:15:11.532518 #1] DEBUG -- : MONGODB | Connection refused - connect(2) for 127.0.0.1:37017
D, [2018-06-04T14:15:12.032037 #1] DEBUG -- : MONGODB | Connection refused - connect(2) for 127.0.0.1:37017
D, [2018-06-04T14:15:12.533348 #1] DEBUG -- : MONGODB | Connection refused - connect(2) for 127.0.0.1:37017
D, [2018-06-04T14:15:13.036087 #1] DEBUG -- : MONGODB | Connection refused - connect(2) for 127.0.0.1:37017

Looking forward to your help/guidance.

FYI I was following this documentation for running a ruby script in docker: https://docs.docker.com/samples/library/ruby/

Ignacio Millán · Accepted Answer · 2018-06-04 15:51:46Z

1

Local ports are not available from inside Docker containers, you only can connect to ports opened in the container or from other containers with --link.

To connect to host's ports you should use the IP for the docker network's gateway.

To get the gateway IP of your container run:

docker inspect --format='{{range .NetworkSettings.Networks}}{{.Gateway}}{{end}}'

Usually it will return 172.17.0.1 (I repeat, this answer is only valid for default network configurations, assuming that the container is connected to a bridge network)

Then you can update the mongo client config:

clientDB = Mongo::Client.new(["172.17.0.1:37017"], :database => 'Database', :user => 'user', :password => 'password')

answered Jun 4, 2018 at 15:51

Ignacio Millán

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kometen · Accepted Answer · 2021-08-13 11:21:39Z

0

You can access mongodb on your computer from docker with host.docker.internal. This (or a similar, can't remember) SO-thread helped me.

answered Aug 13, 2021 at 11:21

kometen

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