Generators in D

[Piotr Szturmaj]

Sean Kelly wrote:
> On May 18, 2011, at 5:21 PM, Piotr Szturmaj wrote:
>
>> Jose Armando Garcia wrote:
>>>>
>>>> If serialization will be clever enough, these fibers could even be shared
>>>> across different servers! This is really a requirement in load balanced
>>>> environments.
>>>>
>>>
>>> A very old research paper (I think it was for the amoeba project)
>>> wrote a long time ago (I don't remember the wording) that is usually a
>>> bad idea to migrate already running tasks (process, thread, fiber,
>>> etc). Leading to the observation that it is probably best to do
>>> offloading/load-balancing before the work is started. That is how most
>>> modern scale-able architectures work. This is just an observation
>>> since you haven't exactly said how to use Fiber to save Http sessions.
>>>
>>
>> There are some cases where it's useful. See SecondLife and EVE online. As for HTTP sessions, imagine some long wizard-like survey. User may fill half of that survey and may come back after week or so. She will start from the last checkpoint.
>> Of course such things are widely done using regular code, but fiber code would be certainly simpler and cleaner, and thus less error-prone.
>> There are of course some issues, f.i. how to deal with multiple requests/opened tabs or security issues. Such serialized fiber should be HMAC'ed and checked for authentication and integrity on deserialization.
>
> Interesting issue.  For example, what if there's a code upgrade?

Yes, that's some serious problem. I guess, I was wrong with these long 
term sessions. I wonder how SecondLife authors got rid of this issue.