Debugging DNS lookup of MariaDB instance.

Question

Hi. My serverless instance in AWS can reach my MariaDB database (RDS) and things work fine but things don't work if I try to connect from my local computer. The problem appears and disappears randomly, It works some days and it doesn't work on other days.

Here is the result of ping to MYDB.eu-west-1.rds.amazonaws.com
```
PING MYDB.eu-west-1.compute.amazonaws.com (52.209.116.0) 56(84) bytes of data.
---MYDB.eu-west-1.compute.amazonaws.com ping statistics ---
13 packets transmitted, 0 received, 100% packet loss, time 12448ms
```
Here is what it looks like if I connect with PMA in a docker container:
![Enter image description here](https://repost.aws/media/postImages/original/IMF16lOoiyTbGhuqcAm781tA)

I tried to reboot the DB.

Is there something else I should try?

Answer

How many connections per second are being made from the EC2 instance to the RDS instance? You may be running into a DNS quota issue where the single EC2 instance is sending too many packets too quickly to resolve the RDS DNS entry.

Info about this: https://docs.aws.amazon.com/vpc/latest/userguide/vpc-dns.html#vpc-dns-limits

Debugging DNS lookup of MariaDB instance.

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