I can only see a few most recent entries in the log, most likely because
the log was rolled over and earlier entries are now in an archived and
compressed log. Could you also attach any compressed dbus logs that are
kicking around?
Looking through what I can see, there are a number of "FAILED
PREVIOUSLY" entries, including one for "Friday Night in San Francisco",
for which we know that 7digital indeed has artwork.

The FAILED PREVIOUSLY entries come about because, on a previous attempt
to retrieve artwork, 7digital has *authoritatively* told us that it does
not have artwork for this album (by returning a 404 HTTP error).
Unfortunately, 7digital has a habit of doing that when part of its index
is down. The error code we get is wrong; 7digital should return a
temporary error instead of an authoritative error in this case.
Unfortunately, 7digital also returns the same 404 error for albums for
which it truly does not have artwork, so we cannot distinguish a
temporary failure from a permanent one.

To avoid hammering the radio and network quota with futile attempts to
get artwork that does not exist, we remember the 404 error; if we get a
request for the same album again, we immediately return FAILED
PREVIOUSLY. However, these failure entries time out after one week, and
we try to retrieve artwork for a failed album again once the timeout
expires.

The upshot of all this is that the problem will fix itself aftera  week
(assuming that 7digital has artwork at the time the next attempt is
made).

So, there is no bug here. Given what 7digital is telling us, the
behavior is exactly as intended, and the problem will rectify itself
automatically.

The only thing we could do is shorten the retry timeout. There is trade-
off involved here: a shorter retry timeout means that the problem will
fix itself sooner, but it also means that we will try more often to get
artwork for albums that indeed do not exist on 7digital (and, most
likely, never will).

Note that, once a request to 7digital succeeds, we cache it and,
thereafter, the album art will kick around pretty much forever, unless
you have truly gigantic media collection. (But, even then, artwork is
cached in LRU order, so anything you look at reasonably frequently will
always be in the cache.)

I'll leave this bug open for now. Please let me know whether the problem
rectifies itself after a week.

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https://bugs.launchpad.net/bugs/1559522

Title:
  Thumbnailer fails to fetch thumbnails from Internet

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