Neil Turner's Blog

Blogging about technology and randomness since 2002

Avoiding duplicate trackbacks

Phil has unleashed a trackback hack that only allows you to ping an entry once with a particular URL. This has the advantage of stopping multiple trackback pings, and potentially alleviating crapflooders. I’ve applied it here.
He also has another hack, which fetches the URL that is being pinged and looks to see if there’s any trackback RDF data in it. If so, the ping is let through, otherwise it’s blocked – therefore you would only be able to ping something if you accepted pings yourself. I didn’t apply that because I’m a little bit more open and because it would mean a greater risk of trackback timeouts, which, by the way, you can help to prevent by reading my Stopping Trackback Timeouts at the both ends article.
Stephen Riha also has a more elaborate hack – if a duplicate ping is received, it examines the excerpt, and if it is different, the existing ping is updated; otherwise it is discarded. I decided not to go with that one as I don’t think I’d find it necessary. But it’s there if you want to use it.

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