Connecting Node-Red to Mariadb within Docker - docker

Question

Evening all,
Setting up a fairly straightforward Mosquitto -> Node-Red -> Mariadb deployment, from docker-compose. Compose file as below:
version: '3.8'
services:
mqtt:
container_name: mosquitto
image: eclipse-mosquitto:latest
restart: always
ports:
- "1883:1883"
volumes:
- ./mosquitto.conf:/mosquitto/config/mosquitto.conf
- /mosquitto/data
- /mosquitto/log
nodered:
container_name: node-red
image: nodered/node-red:latest
restart: always
ports:
- "1880:1880"
volumes:
- node_red_user_data:/data
links:
- "mariadb:mariadb"
mariadb:
container_name: mariadb
image: mariadb:latest
restart: always
command: --default-authentication-plugin=mysql_native_password
ports:
- "3306:3306"
- "33060:33060"
environment:
- MYSQL_RANDOM_ROOT_PASSWORD=yes
- MYSQL_DATABASE=test
- MYSQL_USER=testuser
- MYSQL_PASSWORD=password
volumes:
- mariadb_data_container:/var/lib/mysql
volumes:
mariadb_data_container:
node_red_user_data:
mosquitto_persistence:
networks:
default:
name: primary
Mosquitto to Node-Red is working well enough, and I've set up the database and table in mariadb, but I'm not having any luck getting Node-Red to talk to Maria. Getting this error thrown back at me.
Error: connect ECONNREFUSED 127.0.0.1:3306
The Node-red node in question is as follows:
[{"id":"d93d7d2b.ee27f","type":"mysql","z":"ec0540ab.8b4e2","mydb":"68416de0.8f91a4","name":"XDK Environmental Data","x":750,"y":260,"wires":[["d0d7439f.9b88d"]]},{"id":"68416de0.8f91a4","type":"MySQLdatabase","z":"","name":"Write to mariadb","host":"localhost","port":"3306","db":"XDK_FEM","tz":""}
Full Node-red flow here, in case that's in some way useful.
[{"id":"ec0540ab.8b4e2","type":"tab","label":"MQTT_MYSQL_write","disabled":false,"info":""},{"id":"772011e7.51dd4","type":"mqtt in","z":"ec0540ab.8b4e2","name":"XDK1_Output","topic":"BCDS/XDK110/example/out","qos":"2","datatype":"utf8","broker":"ac9b691.6c35998","x":90,"y":260,"wires":[["f7d34d6b.63919","8336338b.e648c"]]},{"id":"d0d7439f.9b88d","type":"debug","z":"ec0540ab.8b4e2","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":990,"y":260,"wires":[]},{"id":"d79d4ae0.fcf958","type":"function","z":"ec0540ab.8b4e2","name":"Create query in topic","func":"var out = \"INSERT INTO XDK1_raw (timestamp,message)\"\nout = out + \"VALUES ('\" + new Date().toISOString() + \"','\" \nout = out + msg.payload + \"');\"\nmsg.topic=out;\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":500,"y":260,"wires":[["d93d7d2b.ee27f"]]},{"id":"9b43a338.781","type":"comment","z":"ec0540ab.8b4e2","name":"Log everything","info":"","x":100,"y":200,"wires":[]},{"id":"d93d7d2b.ee27f","type":"mysql","z":"ec0540ab.8b4e2","mydb":"68416de0.8f91a4","name":"XDK Environmental Data","x":750,"y":260,"wires":[["d0d7439f.9b88d"]]},{"id":"f7d34d6b.63919","type":"debug","z":"ec0540ab.8b4e2","name":"","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":310,"y":180,"wires":[]},{"id":"8336338b.e648c","type":"json","z":"ec0540ab.8b4e2","name":"","property":"payload","action":"str","pretty":true,"x":270,"y":300,"wires":[["cbee55ed.b7a668","d79d4ae0.fcf958"]]},{"id":"cbee55ed.b7a668","type":"debug","z":"ec0540ab.8b4e2","name":"","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":480,"y":380,"wires":[]},{"id":"ac9b691.6c35998","type":"mqtt-broker","z":"","name":"XDK_Mosquitto","broker":"192.168.1.115","port":"1883","clientid":"","usetls":false,"compatmode":false,"keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","closeTopic":"","closeQos":"0","closePayload":"","willTopic":"","willQos":"0","willPayload":""},{"id":"68416de0.8f91a4","type":"MySQLdatabase","z":"","name":"Write to mariadb","host":"localhost","port":"3306","db":"XDK_FEM","tz":""}]
I've tried various combinations of ports and configs, and after digging myself deeper into a hole I've just reset everything to start from scratch.
Any insight gratefully received!
EDIT
I realise this isn't a very helpful update for anyone facing the same image, but in the end I deleted the container and started again from the docker-compose and it worked. Lord only knows. Working theory is that before hitting on the right answer (using 'mariadb' instead of 'localhost') I broke something trying a wrong answer.

Answer 1

The important thing to remember is that each container has it's own loopback device (lo, 127.0.0.1) and the host for the containers has it's own as well and they are all totally separate.
So you can not reference the MariaDB container as 127.0.0.1 from the Node-RED container as that address points to the Node-RED container.
You need to use the hostname mariadb not 127.0.0.1 when entering the details or the mariadb config node.