6 ms·

The elephant in the room here of course is this: https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCeiX5fCnF https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCei

by cedricd 13y ago

The elephant in the room here of course is this: https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCeiX5fCnF https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCeiX5fCnF

hackerboos 13y ago
True. This hash should be appended like so: https://news.ycombinator.com/page3/x?fnid=b7VO4wED8MRumCeiX5fCnF https://news.ycombinator.com/page3/x?fnid=b7VO4wED8MRumCeiX5...
ancarda 13y ago
I never understood why HN has such a peculiar URL for accessing pages. It times out after a while too, is that to stop crawlers?
- deleted 13y ago
  [deleted]
- Robin_Message 13y ago
  They are ids to lookup closures in a database. They time out to stop the database overflowing ;) It's called continuation-based web development [1], popular with Lisp and Smalltalk-based web servers (because who else has continuations?) [1] http://en.wikipedia.org/wiki/Continuation#In_Web_development http://en.wikipedia.org/wiki/Continuation#In_Web_development
  - jgrahamc 13y ago
    There's no database. EDIT: to all the people arguing with me. Read the source code to Hacker News. (= fns* (table) fnids* nil timed-fnids* nil) ; count on huge (expt 64 10) size of fnid space to avoid clashes (def new-fnid () (check (sym (rand-string 10)) ~fns* (new-fnid))) (def fnid (f) (atlet key (new-fnid) (= (fns* key) f) (push key fnids*) key)) (mac afnid (f) `(atlet it (new-fnid) (= (fns* it) ,f) (push it fnids*) it)) They are in memory. Which is why they expire randomly when the HN process is restarted.
    - gcr 13y ago
      Racket (arc's host language) keeps continuations on the filesystem, or you can write your own "stuffer" to do what you want with them (store them in a database or whatever). But you have to keep them somewhere or else (assuming the server uses continuations) you can't keep track of the user's path through your code as they click through links and such. Racket does have an option to serialize the continuations, gzip them, sign them with HMAC, and then send all of that to the client so the server doesn't have to keep track of anything, but HN doesn't use it. See http://docs.racket-lang.org/continue/#(part._.Advanced_.Control_.Flow) http://docs.racket-lang.org/continue/#(part._.Advanced_.Cont... for a quick introduction.
      - epochwolf 13y ago
        HN doesn't use racket. It's a custom lisp based on scheme.
        gcr 13y ago
        Sure it does. HN is written in "Arc": https://github.com/wting/hackernews https://github.com/wting/hackernews Arc runs on Racket: http://en.wikipedia.org/wiki/Arc_(programming_language) http://en.wikipedia.org/wiki/Arc_(programming_language) See the "OS" section where it says "runs on the Racket compiler" See also the Arc source code, https://github.com/Pauan/ar/blob/arc/nu/arc https://github.com/Pauan/ar/blob/arc/nu/arc Note the "#lang racket" at the top.
    - scotth 13y ago
      Depends on what you consider a database.
    - ahknight 13y ago
      There's always a database.
    - oh_sigh 13y ago
      Then where is the data that is associated with "b7VO4wED8MRumCeiX5fCnF" stored? How is that data requested? There certainly is a database, it is just most likely not a traditional database that most people think of.
  - tveita 13y ago
    Oh, wow. I had assumed that people who visited around the same time got the same next page URL, maybe as part of a caching strategy or something. This way seems impractical, TBH. Certainly for the user - the expiration a bit of a nuisance, as I'll get it more often than not if I read a couple of stories and then click 'More'.
- kalmar 13y ago
  I believe it's a continuation-style server—hence fnid: function id—and the continuations are only kept around in memory for ~5 minutes.
  - lucian1900 13y ago
    I never understood why the continuation couldn't instead be addressed by a URL path. It could even get constructed from URL/query data if it moves out of memory, so keeping them in memory would only be a caching mechanism.
    - pfarrell 13y ago
      Yes, but the way hn works, the continuations map uri's to browser sessions so they can be expired on a more granular basis than all at once or lru or what have you. I'm guessing here, though, I've not looked through the code. [addendum] I Reread your comment and realized that wasn't what you meant at all. What would be the benefit of path based uris over query string params in hn's case? I only see how they be equal, not better.
      - lucian1900 13y ago
        I meant that the continuation could be identified by (session_id, URL data), and re-created based on this data if it goes missing. URL data can come from path or query string, it doesn't matter.
    - acdha 13y ago
      Every continuation framework I've looked at radiates an intense desire to treat the web as something other than what it actually is.

by cedricd 13y ago

The elephant in the room here of course is this: https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCeiX5fCnF https://news.ycombinator.com/x?fnid=b7VO4wED8MRumCeiX5fCnF

hackerboos 13y ago

True. This hash should be appended like so: https://news.ycombinator.com/page3/x?fnid=b7VO4wED8MRumCeiX5fCnF https://news.ycombinator.com/page3/x?fnid=b7VO4wED8MRumCeiX5...

ancarda 13y ago

I never understood why HN has such a peculiar URL for accessing pages. It times out after a while too, is that to stop crawlers?

deleted 13y ago
[deleted]
Robin_Message 13y ago
They are ids to lookup closures in a database. They time out to stop the database overflowing ;) It's called continuation-based web development [1], popular with Lisp and Smalltalk-based web servers (because who else has continuations?) [1] http://en.wikipedia.org/wiki/Continuation#In_Web_development http://en.wikipedia.org/wiki/Continuation#In_Web_development
- jgrahamc 13y ago
  There's no database. EDIT: to all the people arguing with me. Read the source code to Hacker News. (= fns* (table) fnids* nil timed-fnids* nil) ; count on huge (expt 64 10) size of fnid space to avoid clashes (def new-fnid () (check (sym (rand-string 10)) ~fns* (new-fnid))) (def fnid (f) (atlet key (new-fnid) (= (fns* key) f) (push key fnids*) key)) (mac afnid (f) `(atlet it (new-fnid) (= (fns* it) ,f) (push it fnids*) it)) They are in memory. Which is why they expire randomly when the HN process is restarted.
  - gcr 13y ago
    Racket (arc's host language) keeps continuations on the filesystem, or you can write your own "stuffer" to do what you want with them (store them in a database or whatever). But you have to keep them somewhere or else (assuming the server uses continuations) you can't keep track of the user's path through your code as they click through links and such. Racket does have an option to serialize the continuations, gzip them, sign them with HMAC, and then send all of that to the client so the server doesn't have to keep track of anything, but HN doesn't use it. See http://docs.racket-lang.org/continue/#(part._.Advanced_.Control_.Flow) http://docs.racket-lang.org/continue/#(part._.Advanced_.Cont... for a quick introduction.
    - epochwolf 13y ago
      HN doesn't use racket. It's a custom lisp based on scheme.
      - gcr 13y ago
        Sure it does. HN is written in "Arc": https://github.com/wting/hackernews https://github.com/wting/hackernews Arc runs on Racket: http://en.wikipedia.org/wiki/Arc_(programming_language) http://en.wikipedia.org/wiki/Arc_(programming_language) See the "OS" section where it says "runs on the Racket compiler" See also the Arc source code, https://github.com/Pauan/ar/blob/arc/nu/arc https://github.com/Pauan/ar/blob/arc/nu/arc Note the "#lang racket" at the top.
  - scotth 13y ago
    Depends on what you consider a database.
  - ahknight 13y ago
    There's always a database.
  - oh_sigh 13y ago
    Then where is the data that is associated with "b7VO4wED8MRumCeiX5fCnF" stored? How is that data requested? There certainly is a database, it is just most likely not a traditional database that most people think of.
- tveita 13y ago
  Oh, wow. I had assumed that people who visited around the same time got the same next page URL, maybe as part of a caching strategy or something. This way seems impractical, TBH. Certainly for the user - the expiration a bit of a nuisance, as I'll get it more often than not if I read a couple of stories and then click 'More'.
kalmar 13y ago
I believe it's a continuation-style server—hence fnid: function id—and the continuations are only kept around in memory for ~5 minutes.
- lucian1900 13y ago
  I never understood why the continuation couldn't instead be addressed by a URL path. It could even get constructed from URL/query data if it moves out of memory, so keeping them in memory would only be a caching mechanism.
  - pfarrell 13y ago
    Yes, but the way hn works, the continuations map uri's to browser sessions so they can be expired on a more granular basis than all at once or lru or what have you. I'm guessing here, though, I've not looked through the code. [addendum] I Reread your comment and realized that wasn't what you meant at all. What would be the benefit of path based uris over query string params in hn's case? I only see how they be equal, not better.
    - lucian1900 13y ago
      I meant that the continuation could be identified by (session_id, URL data), and re-created based on this data if it goes missing. URL data can come from path or query string, it doesn't matter.
  - acdha 13y ago
    Every continuation framework I've looked at radiates an intense desire to treat the web as something other than what it actually is.