Hi Herbert,
It sounds like you're interested in running just one client computation at
once? Hence you don't have a disambiguation problem -- if the total memory
footprint crosses a threshold you know who to blame.
At least this seems easier than needing a per-computation or per-IO-thread
caps. By the way, the folks who implement Second Life did an interesting
job of that -- they hacked Mono to be able to execute untrusted code with
resource bounds.
Cheers,
-Ryan
On Thu, Apr 19, 2012 at 6:45 AM, Herbert Valerio Riedel
Hello GHC Devs,
One issue that's been bothering me when writing Haskell programs meant to be long-running processes performing computations on external input-data in terms of an event/request-loop (think web-services, SQL-servers, or REPLs), that it is desirable to be able to limit resource-usage and be able to "contain" the effects of computations which exhausts the resource-limits (i.e. w/o crashing and burning the whole process)
For the time-dimension, I'm already using functions such as System.Timeout.timeout which I can use to make sure that even a (forced) pure computation doesn't require (significantly) more wall-clock time than I expect it to.
But I'm missing a similar facility for constraining the space-dimension. In some other languages such as C, I have (more or less) the ability to check for /local/ out-of-memory conditions (e.g. by checking the return value of e.g. malloc(3) for heap-allocations, or by handling an OOM exception), rollback the computation, and be able to skip to the next computation request (which hopefully requires less memory...)
So, is there already any such facility provided by the GHC Platform I've missed so far?
...and if not, would such a memory-limiting facility be reconcilable with the GHC RTS architecture?
Cheers, hvr --
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