Why does my RSS feed duplicate some entries?

Question

Hello,

when reading my RSS feed with Thunderbird feed reader, some entries are duplicated. Google reader does not have the same problem.

Here is the faulty feed http://plcoder.net/rss.php?rss=Blog

There is a problem, but where?

Regards, Cédric

update : I add guid but the problem remain. Anothers feeds does not duplicate like mine, so I will re-work on this module and replace this old good code.

conclusion : I re-work completely the rss generator code, and it's ok. I think I was using a very old version of RDF.

Answer 1

I had the same problem... I switched to Google's feed and it's now fixed, never knew the exact cause though

http://feedproxy.google.com/juanformoso

Answer 2

Thunderbird has a few bugs with duplicating feed entries, perhaps it's just one of them showing up?

Answer 3

Try adding a <guid> tag to each item, giving it a permalink. i.e.:

<item rdf:about="http://plcoder.net/?doc=2134&amp;amp;amp;titre=mon-pc-se-la-pete"&gt;
  <link>http://plcoder.net/?doc=2134&amp;amp;amp;titre=mon-pc-se-la-pete&lt;/link&gt;
  <guid>http://plcoder.net/?doc=2134&amp;amp;amp;titre=mon-pc-se-la-pete&lt;/guid&gt;
  ...
</item>

Without a GUID, if any of the content in the post changes, your RSS aggregator might think that it is a new post. With the GUID, even if the content of that item changes, your RSS aggregator should just update the post, instead of treating it as a new item.

Answer 4

I have experienced this issues with some of my own feeds. What has happened is I start off with a list of entries like this:

Item A
Item B
Item C

The client downloads them and everything is fine. Then I add a new item, so the feed reads as:

Item D
Item A
Item B

D shows up in the reader.

But then I decide I don't want that item, so the list reverts to:

Item A
Item B
Item C

When Thunderbird reads this, it'll count C as a new item. I am using a GUID element, so I doubt that's the problem. I think it's got more to do with Thunderbird's parser not taking older elements into consideration.

The long-winded workaround is to "remember" what items you've already published and have since been pushed off the end of the list by new items. You'll basically need to keep a current list of items in the feed and when you delete items from it, cut it short until there are new items to replace it.

Answer 5

At least with Thunderbird 2.0.0.21 the problem is that TBird doesn't seem to respect GUID-tags but it does respect the channel's pubDate-tag. Thus if pubDate is more recent than with last reading, TBird will read all entries (it seems).

I don't know what would happen if channel's pubDate-tag is missing though...