I’ve been thinking of self hosting a mastodon (gotosocial, more specifically) + a matrix server on an old computer I have, but sometimes I might need to turn it off for 2 days or more (not to mention some energy or internet outages that might happen here)
I suppose with the mastodon part the server will properly sync and download whatever’s been missing, but I’m not entirely sure that’ll be the case with matrix. If anyone sent me a DM on there while my server was down, would it get through after it was back up?
Sort of, but not really. It’s a pub/sub ecosystem, so if your services are offline, they aren’t going to be pulling the delta of missed data beyond a threshold. That’s why clients are clients, because they are built to do this for this purpose.
It wouldn’t make sense for a deployment acting as an active instance to act like a client in the way you’re describing, because the services are configured and tuned to NOT act that way, but ingest data available at time of publish to the endpoints they are subscribed to.