Cannot connect to a working, Dockerized Mongo ReplSet - mongodb

Question

I'm trying to create a Mongo ReplicaSet running locally, using the following docker-compose file:
version: '2.0'
services:
db01:
image: mongo:3.4
mem_limit: 512m
restart: always
ports:
- "27017:27017"
volumes:
- datadb01:/data/db
- ./etc/mongod.conf:/etc/mongod.conf
command: mongod --smallfiles --noIndexBuildRetry --replSet rs0
container_name: db01
networks:
- mongo
db02:
image: mongo:3.4
mem_limit: 512m
restart: always
ports:
- "27018:27017"
volumes:
- datadb02:/data1/db
- ./etc/mongod.conf:/etc/mongod.conf
command: mongod --smallfiles --noIndexBuildRetry --replSet rs0
container_name: db02
networks:
- mongo
So this actually seems to work! I won't post the whole thing but when I run rs.status() I get this:
{
"set" : "rs0",
...
"ok" : 1
}
However, when I try to connect to the replicaSet, rather than just a single node, I get this bunch of error logs:
~/utils/infrastructure/content-repl-set [replay-content*]: mongo --host rs0/127.0.0.1:27017,127.0.0.1:27018
MongoDB shell version v4.0.0
connecting to: mongodb://127.0.0.1:27017,127.0.0.1:27018/?replicaSet=rs0
2018-09-10T17:50:42.173-0400 I NETWORK [js] Starting new replica set monitor for rs0/127.0.0.1:27017,127.0.0.1:27018
2018-09-10T17:50:42.176-0400 I NETWORK [js] Successfully connected to 127.0.0.1:27018 (1 connections now open to 127.0.0.1:27018 with a 5 second timeout)
2018-09-10T17:50:42.177-0400 I NETWORK [js] changing hosts to rs0/db01:27017,db02:27017 from rs0/127.0.0.1:27017,127.0.0.1:27018
2018-09-10T17:50:42.177-0400 I NETWORK [ReplicaSetMonitor-TaskExecutor] Successfully connected to 127.0.0.1:27017 (1 connections now open to 127.0.0.1:27017 with a 5 second timeout)
2018-09-10T17:50:42.684-0400 W NETWORK [js] Unable to reach primary for set rs0
My best guess from that is that the mongo shell (and other mongo drivers, such as pymongo) isn't aware of the container name that I've specified in the docker container. Is there a way to expose this information to my local machine? Or am I off the mark? Thanks for your help

Answer 1

Are you using MacOS? if so, it seems those internal IP addresses in docker are unreachable because the docker (Linux) bridge network is not reachable from the macOS host.
More of it here: https://docs.docker.com/docker-for-mac/networking/