I have the following architecture
- AWS AppRunner instance running a Node API
- RDS Postgres instance
- Both live in a VPC
I'm deploying my system via Terraform, though I'm not sure that's relevant - I can reproduce this behavior via the AWS Console.
Upon provisioning my AppRunner instance, if my app attempts to connect to the database (RDS) immediately when it boots (my app runs migrations), it's unable to connect and the provisioning fails. It fails due to some DNS issue:
Failed to start server: Error: getaddrinfo EAI_AGAIN...
at GetAddrInfoReqWrap.onlookup [as oncomplete] (node:dns:107:26)
This error seems to happen if my app attempts to connect to RDS when it boots, and it happens over and over.
If I temporarily disable the database connection activity, and allow my app to boot it succeeds. Then, if I re-enable the database activity and redeploy, it works.
It seems that AppRunner needs to boot once successfully before it can successfully establish a connection to RDS in the same VPC.
Has anyone experienced this? Is my assumption above (the required initial successful boot) correct, or am I misunderstanding what's happening?