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Comment by rms | Hacker News Reader

I usually only get it if I have a comment reply open for a long time before clicking add. Feels like the continuation lasts for about 20 minutes.

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There's no set timeout. They're kept in a queue.

With the load going up so much (causing the crashes) it also means the links expire faster. I would guess in under 10 minutes sometimes, maybe under 5.

Pretty sure that's what pg's said it is. Personally, that's way too short, as I'll leave threads open for half a day without reading it, then can't comment.

I don't see any fundamental reason why continuations have to expire so fast.

Because they take up ram on the server. 20 minutes is standard session timeout for most session based web frameworks.

I wonder - would it be technically feasible to page the continuations out to temporary files on the server? Kind of like cookies, but on the server instead of the client!

Technically possible. There are a few Scheme implementations that have persistent continuation (all I know is JVM based ones). Also this page contains a link to the slides that talks about persistent delimited continuation in OCaml: http://logic.cs.tsukuba.ac.jp/Continuation/program.html

Making continuations serializable may cost its implementation, so whether it scales well for yc.news is anothoer question. I don't know the answer for it.

In lua at least, continuations have a 1k stack overhead in memory per continuation. I believe they are serializable as well... I'll have to double-check that. At 1k+ a pop they're not cheap, but are manageable.

Having my tabs open last for a couple of days instead of 30 minutes would make the site more pleasant for me.

Reason enough not to use a 'session based web framework'.

If PHP can do it...

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