When using docker swarm node in the overlay network I lost connectivity if connecting from another host

Question

Created my service using the following command with docker:

docker service create --mount 
type=bind,src=/tmp/postgres,dst=/var/lib/postgresql/data 
--name dev_db 
--network mynetwork -p 5432:5432 -d postgres

The problem is that if I don't use the overlay network --network, I can connect to this docker instance from another host by just using the simple postgresql client:

psql -h (ipofthehost) mydatabase -Umydatabase

but now that I want to connect to it from another host I get this error:

psql: could not connect to server: Connection refused
    Is the server running on host "ipofdehost" and accepting
    TCP/IP connections on port 5432?

Which is telling me that it might be running but it can't see it. I verified if the service is running with:

docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE                          PORTS
8hr0qwtca230        dev_db              replicated          1/1                 postgres:latest                *:5432->5432/tcp

I verified with ss to see if the service is listening:

State       Recv-Q Send-Q                                               Local Address:Port                                                              Peer Address:Port              
LISTEN      0      128                                                              *:22                                                                           *:*                  
LISTEN      0      100                                                      127.0.0.1:25                                                                           *:*                  
LISTEN      0      128                                                             :::22                                                                          :::*                  
LISTEN      0      128                                                             :::5432                                                                        :::*                  
LISTEN      0      128                                                             :::12376                                                                       :::*                  
LISTEN      0      100                                                            ::1:25                                                                          :::*                  
LISTEN      0      128                                                             :::443                                                                         :::* 

It seems like it is listening because of the line: :::5432, but for me that seems like it is only for ipv6 connections, so how can I make it to listen for ipv4 connections?, all I have changed was that I connected that node to the overlay network so I don't understand why if I made it to expose the ports is not making available publicly.

Thank you!

Answer 1

To explicitly set listen on overlay host nic, first identify the IP address of the overlay interface, then modify your run commands to:

docker service create --mount 
type=bind,src=/tmp/postgres,dst=/var/lib/postgresql/data --name dev_db --network mynetwork -p host-overlay-ipv4:5432:5432 -d postgres

Replace host-overlay-ipv4 with the correct overlay IPv4 address.

More information on the Docker CLI can be found on this wiki.