MongoDB cluster timeout while connecting to Node-RED - node.js

Question

I am facing troubles while trying to connect my MongoDB:3.4 cluster to Node-RED:2 using Docker Swarm.
My environment consists of one leader machine, two workers with one Mongo node on each (mongo1 and mongo2), and the Node-RED container on one of the workers.
I successfully initiated my cluster with the below command:
rs.initiate({
_id : "rs1",
members: [
{ _id: 1, host: "mongo1:27017" },
{ _id: 2, host: "mongo2:27017" }
]
})
A connection with Mongo Express was successful on both the primary and secondary nodes of my cluster.
But when I tried to connect to the cluster from node-RED using the node-red-node-mongodb module, I got the following error:
MongoNetworkError: failed to connect to server [mongo2:27017] on first connect [MongoNetworkTimeoutError: connection timed out
at connectionFailureError (/data/node_modules/mongodb/lib/core/connection/connect.js:362:14)
at Socket.<anonymous> (/data/node_modules/mongodb/lib/core/connection/connect.js:330:16)
at Object.onceWrapper (events.js:519:28)
at Socket.emit (events.js:400:28)
at Socket._onTimeout (net.js:495:8)
at listOnTimeout (internal/timers.js:557:17)
at processTimers (internal/timers.js:500:7)]
This is how the MongoDB node was configured:
Host: mongo1,mongo2
Connection topology: RelicaSet/Cluster (mongodb://)
Connection options: replicaSet=rs1&tls=true&tlsAllowInvalidCertificates=true&wtimeoutMS=10000&slaveOk=true
And these are the relevant parts of the docker-compose.yml file:
version: '3.4'
services:
NodeRed:
user: root
networks:
- mynetwork
volumes:
- /home/ssmanager/nfsdata/nodered:/data
- /home/ssmanager/nfsdata/records:/data/records
- /home/ssmanager/nfsdata/cdr:/data/cdr
- /home/ssmanager/nfsdata/html/decrypted_temp:/data/records/decrypted
image: nodered/node-red:2
deploy:
placement:
constraints:
- "node.hostname!=ssmanager3"
endpoint_mode: dnsrr
mode: replicated
replicas: 1
update_config:
delay: 10s
restart_policy:
condition: any
max_attempts: 5
mongo1:
image: mongo:3.4
command: mongod --replSet rs1 --noauth --oplogSize 3
environment:
TERM: xterm
volumes:
- /etc/localtime:/etc/localtime:ro
networks:
- mynetwork
deploy:
replicas: 1
placement:
constraints:
- node.labels.mongo.replica == 1
- "node.hostname!=ssmanager3"
mongo2:
image: mongo:3.4
command: mongod --replSet rs1 --noauth --oplogSize 3
environment:
TERM: xterm
volumes:
- /etc/localtime:/etc/localtime:ro
networks:
- mynetwork
deploy:
replicas: 1
placement:
constraints:
- node.labels.mongo.replica == 2
- "node.hostname!=ssmanager3"
express:
container_name: express
image: mongo-express:0.54.0
environment:
ME_CONFIG_BASICAUTH_USERNAME: admin
ME_CONFIG_BASICAUTH_PASSWORD: password
ME_CONFIG_MONGODB_ENABLE_ADMIN: "true"
ME_CONFIG_MONGODB_PORT: 27017
ME_CONFIG_MONGODB_SERVER: mongo1
ME_CONFIG_MONGODB_URL: mongodb://mongo:27017
ME_CONFIG_REQUEST_SIZE: 100Mb
command:
- "mongo-express"
networks:
- mynetwork
deploy:
mode: replicated
replicas: 1
placement:
constraints:
- "node.hostname!=dcsynmgr01"
- "node.hostname!=ssmanager3"
ports:
- target: 8081
published: 8081
protocol: tcp
mode: host
networks:
host_mode:
external:
name: 'host'
mynetwork:
attachable: true