[Ur] Error triggers unlimited retry

[Adam Chlipala]

On 08/06/2013 09:42 AM, Sergey Mironov wrote:
> I'm facing following error message while running examples
>
> Error triggers unlimited retry: Couldn't allocate new heap chunk 
> contiguously; increasing size to 128
>
> What does it mean? Is it dangerous?

Ah, a perfect question to follow up on my reply to the last question, 
warning against exposing non-transactional effectful operations with the 
FFI. :D

No, this error message isn't dangerous.  It just means that the runtime 
system decided to roll back and restart a transaction, to allow 
allocation of more memory.  (Ur/Web doesn't use garbage collection, so a 
transaction restarts whenever a conventional garbage-collected system 
would instead grow the heap and copy old objects over.)

In particular, you should expect to see the message you quoted several 
times at the start of each thread, as it grows its heap size 
exponentially to fit the requirements of the requests it receives.