Sabnzbd fix

[Crosenhain]

Description of the change
Two things:

• I changed the API request path to remove "/sabnzbd" since we set that (or not!) using the URL environment variable
• I modified model.go to handle cases where the map is empty, which would throw a 'runtime error: index out of range [-1]' error

Benefits

The sabnzbd exporter works more reliably, and in more configurations.

Possible drawbacks

There is a possibility the change to the sabnzbd API request path could affect how others have configured their exporter.

Applicable issues

• fixes #

Additional information

[rtrox]

What situation was leading to the map being empty?

I'm a little worried this may actually cause a bug that leads to incorrect metrics. In the collector itself, we compare the cached day string to the one returned from the new Stats object, and if they're not the same, we assume the day has rolled over, and reset the counter:

exportarr/internal/sabnzbd/collector/cache.go

Lines 25 to 40 in e732d20

	func (s serverStatCache) Update(stat model.ServerStat) ServerStats {
	s.total = stat.Total
	if stat.DayParsed != s.todayKey {
	s.articlesTriedHistorical += s.articlesTriedToday
	s.articlesSuccessHistorical += s.articlesSuccessToday
	s.articlesTriedToday = 0
	s.articlesSuccessToday = 0
	s.todayKey = stat.DayParsed
	}
	s.articlesTriedToday = stat.ArticlesTried
	s.articlesSuccessToday = stat.ArticlesSuccess
	return s
	}

So if we receive an empty map due to, for example, a sqlite error on the sab side, we could assume the day has changed too early, resulting in double counting of server stats.

I think we can verify behavior here with a quick unit test that:

1. Creates a new statCache
2. calls Update with a non-zero serverStats object
3. calls Update with a zeroed serverStats object
4. calls Update one more time with the object from step 2.

And then verify that the count is correct.

[rtrox]

The indentation here is what's causing the linter to barf. if you just run go fmt it should fix it up.

[rtrox]

While I understand the thought process here, this would be a breaking change for existing users :-/ Is this actively breaking your setup? If not, we can create an issue and make this change when we do a major version bump. If it is breaking your setup, we probably want to put this behind a flag for now.

[cryptiklemur]

This is actively breaking my setup. Can we introduce a defaulted environment variable here?

[onedr0p]

@rtrox I am ok with this breaking change going into a minor release.

[rtrox]

Summing, it looks like there are a couple changes needed on this PR to land:

1. We need a unittest to verify the empty map handling doesn't break stats. I believe in the interim, an empty map should just result in a 500 until there are stats ready to be returned. While that isn't ideal, I want to make sure the fix maintains the integrity of the stats
2. run go fmt to fix the linter

otherwise, it looks like we're g2g

[Crosenhain]

Sounds good, I've got some time now away from work so I'll have a go at the updates.

[rtrox]

The sab fix portion of this PR should be resolved as of #252 -- going to close this PR in favor of that one, but please feel free to re-open/open new for the api_url change