

Ask HN: "Unknown or expired link." - gsivil

It started appearing very recently in HN when I press More.<p>Is this a feature or a bug in HN? :)
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scrame
It means your session has expired. I usually see it if I come back to the
front page after a few hours (or overnight), but I have been getting it pretty
regularly now.

I suspect that there is a traffic spike, or maybe just more people coming to
the site regularly. Its a growing pain.

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hasenj
PG mentioned somewhere that when he was doing Viaweb, he was storing functions
on the server side in a hash table, so that most urls work by invoking these
functions. This was his way of remembering state between url visits.

It seems that functions expire from this hashtable after a while.

I think that might have seemed like a good idea in 1998, but these days I
think it's just pointless.

[http://people.csail.mit.edu/gregs/ll1-discuss-archive-
html/m...](http://people.csail.mit.edu/gregs/ll1-discuss-archive-
html/msg00681.html)

<http://lib.store.yahoo.net/lib/paulgraham/bbnexcerpts.txt>

    
    
      > One of the problems with using Web pages as a UI is the inherent
      > statelessness of Web sessions.  We got around this by using lexical
      > closures to simulate subroutine-like behavior.  If you understand
      > about continuations, one way to explain what we did would be to
      > say that we wrote our software in continuation-passing style.

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martin1b
Yeah, get that a lot. This error appears whenever a new link is added.
Navigation on the current is invalidated. Annoying bug.

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MattBearman
I have a theory on this:

The url of the 'more' link is some kind of hash of the next page of links at
the time of page load, this is because HN Moves pretty quick, so using the
live data you're likely to miss links between page 1 and 2. (Which is what
happens on 4chan)

Obviously these links have to expire fairly quick as they're pretty unique,
and storing them for much time would use a huge amount of memory. With this in
mind, the life span of these links is probably directly related to the current
load of HN.

Amirite?

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daimyoyo
It means the order of the links in the page you were selecting has changed.
When I get that, I start at the front page again. There's new links there for
you to see.

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plasma
Yeah this is a tad annoying; started reading HN on my iPhone and sometimes I
leave it to keep reading 'more' later and my session expires.

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socialmediaking
This always happens to me, I thought the page was designed to make you always
refresh or something lol.

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phlux
It is the most annoying feature possible.

