feed randomly has red exclamation for no reason

My subscription to “The Setup” has been broken (the red exclamation of death) for a week or more, however (as expected) the feed loads fine and I ensured that it passes w3.org validation, too: http://validator.w3.org/feed/check.cg…

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And these have been broken for a while, too, but are (of course) not broken:

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

http://validator.w3.org/feed/check.cg…

This one does load eventually, but is very slow (validator times out on it, too):
http://validator.w3.org/feed/check.cg…

It’s because every so often these feeds return a 500 error. Check the feed’s statistics and at the bottom of the statistics dialog you’ll see a fetching history. You’ll be able to see exactly what’s wrong there.

The real solution is to not give up when a 500 error is encountered on a known good feed. I haven’t figured out a good metric for when a feed can still be considered good but is encountering temporary errors. Another issue is that when these feeds start throwing 500 errors, they don’t stop for a while. Tumblr does this quite consistently. So I can’t just immediately schedule a re-fetch and hope for the best.

I’m thinking what I could do is just ignore 500-level errors on known good feeds and then finally give up after a day of fetching. I’ll look into doing this. Of course, 400-level errors would immediately kill a feed.

I did as you suggested and consulted the statistics page:

LAST UPDATE
1925 hours ago
EVERY
2 to 2.5 hours
NEXT UPDATE
in -1921 hours

I don’t believe “next update” times should have negative numbers. Of the 8 dead feeds that I checked the statistics page for, all of them had negative next update times.

In TCP, there is an algorithm for exponential backoff, so maybe that would be a better strategy than to “give up” on a feed after some arbitrary time period.

Also, just for grins, I pressed the “Instafetch” button on one that I knew was very much alive and was also important to me.

Amazingly, NB sprang to life and populated with articles. Then, I rechecked the statistics page to see what the deal was and found the following data:

LAST UPDATE
0 minutes ago
EVERY
1 to 1.5 hours
NEXT UPDATE
in 2 hours

FEED
2012-02-01 20:04:06.635000
OK (200)
PAGE
2012-02-01 20:04:07.678000
OK (200)

I guess the solution to my problem is to press the instafetch on all the dead ones and be thankful there aren’t more than there are.

I was just curious and checked another feed that wasn’t exclaimed but also wasn’t updating.

Its feed statistics looked healthy, and its feed and page timestamps show feed 200 and page 200, every 2 hours back until 12:12 today.

However.

The only entry in the items list is from 20 Jan 2012 at 12:00 am but the feed itself contains a posting for 31 Jan 2012 23:59:00Z which does not appear in the items list. Even the magic cure-all Instafetch button doesn’t help this one.

I’ll grant you that the feed doesn’t pass validation, but I bet a euro that lots of feeds don’t pass validation.

I don’t know why I even bothered typing this up, except to serve as a warning to others.

It’s their feed. Check http://giveaway.downloadcrew.com/feed…. There’s only 1 story and it has the same id as the story that NewsBlur is already showing. Their feed is obviously hand-crafted, because it doesn’t work like a valid fee.

Clearly the story is different, but their feed is saying that it’s the same.

It has a different pubDate from the previous entry, though.

Is their feed the only rss feed that doesn’t assign guid values to the entry? I would think these heuristics are what differentiate between feed readers.

If it didn’t assign a guid, that’d be fine. But it is saying that it is the same story.

I have one remaining exclamation that I cannot seem to Instafetch its problems away (well, aside from Tuxera, which seems to be too slow for NB):

http://validator.w3.org/feed/check.cg…

I do not understand if that “Two entries with the same value for atom:updated” warning that w3 cites is what is causing the exclamation, or what.

Ob-stats:

LAST UPDATE
193 hours ago
EVERY
10 to 12.5 minutes
NEXT UPDATE
in 1 minute

The table at the bottom is reporting 200 OK for the page, but nothing for the feed.