Export task stops on "key does not exist" with no way to know if it completed or not

[jaywink]

It looks like an export task will just abort if it can't find a key. This would be ok if the task itself would go into some kind of error state, but polling the task just shows it as finished:

{
	"task_id": 2,
	"task_name": "export_data",
	"params": {
		"export_id": "redacted",
		"include_s3_urls": false,
		"server_name": "domain.tld"
	},
	"start_ts": 1704034098316,
	"end_ts": 1704034914159,
	"is_finished": true
}

It's impossible for a script to follow whether the export finished correctly, except by tailing the logs of the container.

Suggestions:

• An export should try to export everything without stopping on one missing key?
• An is_success or similar boolean on the task to indicate whether the task finishes successfully or not?

[jaywink]

The particular key not found error seems to come from the AppendMedia call btw: https://github.com/turt2live/matrix-media-repo/blob/master/archival/entity_export.go#L69

[turt2live]

#538 at least exposes the error

[turt2live]

The key not found error is a bit more concerning, as it means the media was likely deleted without the knowledge of MMR (or worse, there's a bug in MMR). I feel it's correct to abort on that error, so for now I don't intend to make it non-fatal.

If it turns out the media was deleted because of a MMR bug, please open a new issue with detailed reproduction steps (or a security issue if a user can invoke it).