"ECONNREFUSED" while connecting to docker mysql container in NodeJS application - mysql

Question

I am trying to do the following in the NodeJS application which is running on MAC OSX: (Docker REST API's are used to interact with docker.
API Reference: https://docs.docker.com/engine/reference/api/docker_remote_api_v1.23/)
Create mysql docker container, mapping its port 3306 to one of the host port. This is the docker container configuration POST body:
{
'Env': ['MYSQL_ROOT_PASSWORD=root'],
'Image': 'test-mysql',
'ExposedPorts': {
'3306/tcp': {}
},
'HostConfig': {
'PortBindings': { '3306/tcp': [{}]}
}
Start this newly created mysql docker container.
Fetch the docker container port 3306 host mapping from the host config, by inspecting the container. (Assume the mapping maps mysql container port 3306 to port 32789 of the host)
Create a mysql connection using the following mysql npm module https://www.npmjs.com/package/mysql.
Connection config is:
{
host: dockerHostIp, // 192.168.99.100 -- docker host IP
port: portMappingFromStep3, //32789
user: mySQLUser,
password: mySQLUserPassword,
database: 'mysql'
}
Running all this step sequentially throws an error while setting up mysql connection. It produces following output:
{
[Error: connect ECONNREFUSED 192.168.99.100:32789]
code: 'ECONNREFUSED',
errno: 'ECONNREFUSED',
syscall: 'connect',
address: '192.168.99.100',
port: 32800,
fatal: true
}
But, if I provide a timeout of around 7-8 seconds before establishing up the mysql connection, connection establishes successfully.
Not sure, what is happening over here. I am not able to understand, why without timeout mysql connection is failing. I think it is something related to port mapping. Port mapping is taking some time to setup and providing timeout of roughly 7seconds, is covering up that mapping time.
I am trying to set up an end to end test environment where multiple mysql containers will be running in parallel. Waiting time of 7-8 seconds for the connection setup is a big overhead.
Any help to unravel this mystery will be very helpful.
Thanks