Unable to connect to MySQL instance running on AWS EC2 from AWS Lambda function

Question

I am writing an AWS Lambda function to connect to a MySQL instance running on EC2. I have associated the Lambda function with the same subnet and security group that the EC2 is configured in. I checked the Lambda function's IAM roles and that has AWSLambdaVPCAccessExecutionRole policy attached to it. However I am still not able to connect to the MySQL instance.

I tried allowing traffic from anywhere and that worked but now I am not sure how to connect to the MySQL instance with stricter security rules.

I am using Kotlin to write my lambda function and using serverless to deploy changes to lambda.

I have tried every possible solution available online to make this happen but I haven't had any positive results yet.

Answer 1

You have associated the Lambda function with the same security group. But just that would not do. You also need to add an ingress rule to allow traffic to the security group from itself. Basically, you need to self reference the security group.

Add a rule to allow traffic on the mysql port from sg-xxxxxxxx.