Cannot remotely access PostgreSQL on EC2 instance

Question

I was unable to access a remote AWS postgres database via things like psql -h *EC2ExternalIP* -U *me*. I would get:

psql -h *EC2ExternalIP* -U *me*
psql: could not connect to server: Operation timed out
Is the server running on host *EC2ExternalIP* and accepting
TCP/IP connections on port 5432?

same thing trying a simple telnet connection to this port:

curl telnet://*EC2ExternalIP*:5434
curl: (7) Failed to connect to *EC2ExternalIP* port 5434:
Operation timed out

and even though i could access other services (eg, apache) on this same EC2ExternalIP.

So I poked around at threads like these:

• How to connect to an remote PostgreSQL database on Ubuntu using pgAdmin3?

• Connect to remote EC2 Postgresql database

• https://askubuntu.com/questions/423165/remotely-access-postgresql-database/827358#827358

• https://stackoverflow.com/questions/17770329/cannot-connect-to-postgresql-remotely-on-amazon-ec2-instance-using-pgadmin

and they helped me to ensure I'd made appropriate modifications to postgresql.conf and pg_hba.conf; the right settings for you will depend on your instance's security concerns. But it is still not working.

What should I do to make this DB accessible?

Answer 1

(self-answering in case someone else has these same symptoms!)

Then I stumbled upond Shubham Dipt's post on "PostgreSQL on EC2 (Ubuntu) in AWS", making me aware of the "Security group" layer AWS maintains. It's easy to specify a new one via the AWS console, specifically adding Custom TCP: 5432, Source: Anywhere and SSH TCP:22, Source: Anywhere rules for Inbound:

Then, added this security group to the instance, and it worked for me.