Created question in FIWARE Q/A platform on 14-05-2021 at 07:05
Please, ANSWER this question AT https://stackoverflow.com/questions/67530914/connect-fiware-iot-agent-to-sharded-mongodb

Question:
Connect Fiware IoT Agent to sharded MongoDB

Description:
I am using to following docker-compose file to setup my sharded MongoDB which has 3 shards, 3 config servers and 2 router instances:
version: "3.5"
services:

mongorsn1:
container_name: mongors1n1
hostname: mongors1n1
image: mongo
command: mongod --shardsvr --replSet mongors1 --dbpath /data/db --port 27017
ports:

• 27017:27017
  expose:
• "27017"
  environment:
  TERM: xterm
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/data1:/data/db

mongors1n2:
container_name: mongors1n2
hostname: mongors1n2
image: mongo
command: mongod --shardsvr --replSet mongors1 --dbpath /data/db --port 27017
ports:

• 27027:27017
  expose:
• "27017"
  environment:
  TERM: xterm
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/data2:/data/db

mongors1n3:
container_name: mongors1n3
hostname: mongors1n3
image: mongo
command: mongod --shardsvr --replSet mongors1 --dbpath /data/db --port 27017
ports:

• 27037:27017
  expose:
• "27017"
  environment:
  TERM: xterm
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/data3:/data/db

mongocfg1:
container_name: mongocfg1
image: mongo
command: mongod --configsvr --replSet mongors1conf --dbpath /data/db --port 27017
environment:
TERM: xterm
expose:

• "27017"
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/config1:/data/db

mongocfg2:
container_name: mongocfg2
image: mongo
command: mongod --configsvr --replSet mongors1conf --dbpath /data/db --port 27017
environment:
TERM: xterm
expose:

• "27017"
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/config2:/data/db

mongocfg3:
container_name: mongocfg3
image: mongo
command: mongod --configsvr --replSet mongors1conf --dbpath /data/db --port 27017
environment:
TERM: xterm
expose:

• "27017"
  volumes:
• /etc/localtime:/etc/localtime:ro
• /mongo_cluster/config3:/data/db

mongos1:
container_name: mongos1
image: mongo
hostname: mongos1
depends_on:

• mongocfg1
• mongocfg2
  command: mongos --configdb mongors1conf/mongocfg1:27017,mongocfg2:27017,mongocfg3:27017 --port 27017
  ports:
• 27019:27017
  expose:
• "27017"
  volumes:
• /etc/localtime:/etc/localtime:ro

mongos2:
container_name: mongos2
image: mongo
hostname: mongos2
depends_on:

• mongocfg1
• mongocfg2
  command: mongos --configdb mongors1conf/mongocfg1:27017,mongocfg2:27017,mongocfg3:27017 --port 27017
  ports:
• 27020:27017
  expose:
• "27017"
  volumes:
• /etc/localtime:/etc/localtime:ro

As you can see it is up and running correctly.
docker exec -it mongos1 bash -c "echo 'sh.status()' | mongo "

MongoDB shell version v4.4.6
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session

MongoDB server version: 4.4.6
— Sharding Status —
sharding version:

shards:

active mongoses:
"4.4.6" : 2
autosplit:
Currently enabled: yes
balancer:
Currently enabled: yes
Currently running: no
Failed balancer rounds in last 5 attempts: 0
Migration Results for the last 24 hours:
No recent migrations
databases:

bye

Now here is the docker-compose file I use to connect Orion and the IoT Agent to my MongoDB shards.
version: "3.5"
services:

orion:
image: atos/smbt/orion:2.5.2
hostname: orion
container_name: orion
restart: unless-stopped
ports:

• "1026:1026"
  entrypoint:
• /usr/bin/contextBroker
• -fg
• -multiservice
• -ngsiv1Autocast
• -corsOrigin
• __ALL
  command: -dbhost mongors1n1:27017,mongors1n2:27027,mongors1n3:27037 -rplSet mongors1 -logLevel ERROR -noCache
  healthcheck:
  test: curl --fail -s http://orion:1026/version || exit 1
  networks:
• fiware_mongo_sharding_default

iot-agent:
image: atos/smbt/iotagent-ul:1.15.0
hostname: iot-agent
container_name: iot-agent
restart: unless-stopped
expose:

• "4041"
• "7896"
  ports:
• "4041:4041"
• "7896:7896"
  environment:
• IOTA_CB_HOST=orion
• IOTA_CB_PORT=1026
• IOTA_NORTH_PORT=4041
• IOTA_REGISTRY_TYPE=mongodb
• IOTA_LOG_LEVEL=ERROR
• IOTA_TIMESTAMP=true
• IOTA_CB_NGSI_VERSION=v2
• IOTA_AUTOCAST=true
• IOTA_MONGO_HOST=mongors1n1
• IOTA_MONGO_PORT=27017
• IOTA_MONGO_DB=iotagentul
• IOTA_HTTP_PORT=7896
• IOTA_PROVIDER_URL=http://iot-agent:4041
  networks:
• fiware_mongo_sharding_default

networks:
fiware_mongo_sharding_default:
external: true

Orion is connected to MongoDB but with the IoT Agent I get the following error message.
time=2021-05-14T07:51:51.086Z | lvl=ERROR | corr=28202651-30e1-48dc-88a9-53de603e7e6d | trans=28202651-30e1-48dc-88a9-53de603e7e6d | op=IoTAgentNGSI.DbConn | from=n/a | srv=n/a | subsrv=n/a | msg=MONGODB-001: Error trying to connect to MongoDB: MongoNetworkError: failed to connect to server [mongos1:27019] on first connect [MongoNetworkError: connect ECONNREFUSED 172.20.0.9:27019] | comp=IoTAgent

I have tried different things such as:

• IOTA_MONGO_HOST=mongos1
• IOTA_MONGO_PORT=27019

but to no avail unfortunately. Is there something I am doing wrong?
Thanks in advance for your help.