Solving connectivity issues to AWS with MariaDB on RDS from local machine

Question

I currently develop a small Java web application with following stack: Java 8, Spring Boot, Hibernate, MariaDB, Docker, AWS (RDS, Fargate, etc.). I use AWS to deploy and to run my application. My java web application runs inside of the docker container, which is managed by AWS Fargate; this web application communicates with Amazon RDS (MariaDB instance) via injected secrets and doesn't need to go through public internet for this kind of communication (instead it uses VPC). My recent problems have begun after I've managed to roll out an software update, that enforced me to make some manual database changes with use of MySQL Workbench and I could not perform this because of local connectivity problems.

Therefore my biggest problem right now is the connectivity to the database from the local machine - I simply can't connect to the RDS instance via MySQL Workbench or even from within the IDE (but it used to work before without such problems). MySQL Workbench gave me following error message as a hint:

After check of given hints from MySQL Workbench I've also checked that:

• I use valid database credentials, URL and port (the app in Fargate has the same secrets injected)
• Public accessibility flag on RDS is (temporarily) set to "yes"
• database security group allows MySQL/Aurora connections from my IP Address range (I've also tested the 0.0.0.0/0 range without further luck)

Therefore my question is: what else should I check to find out the reason of my connectivity failure?

Answer 1

After I've changed my laptop network by switching to the mobile internet the connectivity problem was solved - therefore I suspect, that my laptop was not able to establish the socket connection from the previous network (possibly the communication port or DNS was blocked).

Therefore also don't forget to check the network connectivity by establishing a socket connection like it is described in this answer.