[Haskell-cafe] Is Haskell a Good Choice for Web Applications? (ANN: Vocabulink)

Andrew Coppin andrewcoppin at btinternet.com
Wed May 6 16:45:13 EDT 2009

Jason Dagit wrote:
> I don't mean to undermine your marketing efforts, but I don't think
> this is gossip driven.
> I know from experience that lambdabot tends to be leaky.  Otherwise,
> lambdabot wouldn't be running on my server to begin with.  And, even
> so, Cale monitors lambdabot to make sure it is not using too many
> resources (and I complain when/if I notice it).  I have heard similar
> stories related to hpaste and happs.  I have also experienced it with
> writing a forever loop in Haskell that did polling from channels.  I
> would leave my app running for, say, 4 hours and it would be using
> tons of memory.

> I think it's fair to say that keeping the memory usage low of a long
> running Haskell app is hard, but that is a general issue not just a
> Haskell issue.  It's hard in most languages.  I think what we need to
> address this is more information about preventative measures.  What
> programming styles cause the problem and which ones solve it.  I would
> say that I lack confidence recommending anyone to use Haskell for long
> running processes because I don't understand well the problem of
> keeping the usage low.  If it is a well documented problem with
> documented solutions (more than just profiling), then I would regain
> my confidence because I know the problem can be worked around
> reliably.  Does this make sense?  Maybe it's already well documented?
> In particular, we need expert Haskell programmers, such as Don, to
> write more about how they avoid space leaks in long running apps.
> Again, profiling is nice, but that's more of a tuning effort.

Mmm, interesting. Clearly I don't run anything for long enough to notice 
this effect.

(I just had a look at a Haskell program I wrote myself which I happen to 
have running in the background right now. Process Explorer tells me it's 
used 4 hours of CPU time, and it's memory graph is still flat. It was 
reading 106 MB shortly after I started it, and it still says 106 MB now. 
OTOH, it's a fairly trivial program, so...)

But if you're going to advocate more expert knowledge being diseminated, 
I certainly won't argue against that! :-D Export knowledge is something 
it seems difficult to have too much of...

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