Hmm. Strange. First thing:
[experimental]
private_network=true
… is no longer needed. That’s confirmed by Fly e.g
Hence that makes no difference. So yep, you can remove that.
Next, is the app in the same organization as the Redis app? They need to be in order to be able to resolve each other’s internal hostnames.
Next, if you are using Fly’s Redis, based on their guide, I recall that needs a password … Are you providing one from your app? Else that would explain why it can’t connect if not.
Next, it may be worth trying an alternative .internal hostname: Private Networking · Fly Docs Like … what if you swap it for top1.nearest.of.<appname>.internal? Does that work? No real reason why it should but doesn’t hurt to try.
If still no luck, make sure your Redis app binds to IPv6. Again, depends on how it’s set up, but Fly’s private network uses IPv6. So if the Redis app is only listening on IPv4, other apps won’t be able to connect to it using the private network. Look for any references to it binding to 0.0.0.0 or something IPv4-ish.