[blahedo]

It'd work robustly enough if the links didn't expire, and if we believe other posts on this page, the links are expiring due to memory limits on the system. (The other possibility is a timeout, I guess, which is easily fixed.) If it's running out of memory to store the closures it would run out of memory to store the interaction state.

In other words, there's a problem here, but it's not the programming model that pg chose.

[srdev]

Except the links do expire, so its not robust. I expect that when I visit a web page, I can let it sit for an extended period of time before moving on to the next page and have it work. HN doesn't work.

Furthermore, the technique of holding important state authoritatively in memory like this is not a good web-development practice for various reasons. Doubly so if its state data which can be round-tripped. Links should not break when the web server or cache (I'm not sure which one it is) runs low on memory. So yes, there is a problem with the programming model that pg chose.

[gnaritas]

If he hadn't used that technique, there would be no hacker news for you to use at all. You're entirely missing the point that this is a technique to make hobby programming more fun, it's not about being robust or best practice, it's about making programming simpler so pg finds it worth his time to build this site in the first place.

[srdev]

blahedo's point was that the technique was not fundamentally a problem from a robustness point of view, and I disagree with that point. It is a problem, and I was pointing that out.

Your point seems to be that since Hacker News is a "hobby project," that we may forgive sacrificing a bit of robustness to make the programming exercise more pleasant. That point was not clear to me from your original posting. Rather, the point seemed to be that the technique was good because it was clever and fun, and I disagreed with that sentiment.

PG seems to be saying elsewhere that it was used as a rapid prototyping technique. That seems to be a fair justification of the technique, in my estimation.

[dasil003]

> If it's running out of memory to store the closures it would run out of memory to store the interaction state.

Not necessarily. The way I would approach this is to keep the link cache in memory, but have the links contain the minimal necessary state to reconstruct the link from disk-based storage in the case where the cache is gone. That gives the same excellent median performance without any breakage.

[gnaritas]

> The way I would approach this is to keep the link cache in memory, but have the links contain the minimal necessary state to reconstruct the link from disk-based storage in the case where the cache is gone.

It's not a cache, and you clearly don't understand the issue. These are callbacks to closures, embedding the state in the URL is what they attempt to avoid because doing that is tedious.

[dasil003]

Sorry, bad choice of words. I was just shooting from the hip here in response to the parent that suggests you can't both keep something in RAM for the majority of cases and still make it robust.

The fact that embedding state in the URL is tedious is neither here nor there, but in any case it's a pretty garbage excuse. You know what's more tedious than writing code to pass a few integers around in links? Thousands of people losing carefully written paragraphs of enlightened prose on a regular basis. In fact the more carefully considered, the more likely the text is to be lost. If it took 24 hours or even 12 hours for links to expire then maybe you could justify the approach, but it seems to be well under an hour on average before a given closure is purged. This site seems hardly so complex as to be gaining much from a pure continuation approach, and if you can't ease this problem in a lisp then are all of us building services for non-hackers doomed to life of bitter tedium?

[gnaritas]

You seem to not be aware of the architecture of this site, it's all run out of ram, no database; just simple lazy load on demand files on a single server running in a single process. Because of this, memory is tight, that's why those closures are purged. It simply means pg hasn't had the time to convert more of the prototyped code into production stateless code that always works. But that's his prerogative, this site is a hobby for him, he doesn't need to make any excuses about anything. If you don't like his site, go somewhere else.

[dasil003]

There's something on disk isn't there? Or does a power outage mean poof it's all gone?

Anyway, you're totally right that it's his prerogative to build a site however he sees fit, and it's my prerogative to leave, but it's also my prerogative to complain about it and call it half-assed. I do build websites as well, so I'm not just armchair commenting.

[gnaritas]

> Or does a power outage mean poof it's all gone?

Poof the closures are all gone; the state of the articles and comments are of course rebuilt from disk state on an as needed basis.

> I do build websites as well, so I'm not just armchair commenting.

I appreciate that, I just use a similar framework and understand why one would choose to use callbacks and not bother ever replacing them. It has to matter enough to bother and to pg, it doesn't yet.