[erlang-questions] Freezing a process

[Jeffrey Rennie (レニー)]

On Fri, May 28, 2010 at 2:13 PM, Torben Hoffmann
<torben.lehoff@REDACTED> wrote:
>
>
> On Fri, May 28, 2010 at 20:20, Jeffrey Rennie (レニー) <rennie@REDACTED>
> wrote:
>>
>> I've scoured the manuals unsuccessfully, and I've been unable to
>> conjure the right Google query to answer the following question.
>> hibernate() seems to get my half way there, but...
>>
>> Given a pid, can I freeze the process, serialize its stack and heap,
>> send it down the wire and effectively resume it on another node?
>>
>
> Hi Jeffrey.
>
> I cannot give you an answer of how to do it in pure Erlang, but if you are
> using OTP you can take the internal state of the component out and send it
> to another machine.
> Apart from this function to get the state out you will need a start function
> that will restore the saved state from the old process.
>
> The OTP framework has the ability to provide takeover functionality for
> applicaitons, but if my memory serves me correct it involves a restart and
> is in nature more of a resilience feature than a mobility one.
>
> Depending on the details of your requirements there are many subtle things
> to consider in this, e.g., who keeps track of where a process with a given
> role is located (global could be the answer) and if the resume does not work
> how should the behaviour be?
> Ask one of the Ericsson guys and you will probably get an almost infinite
> list.
>
> The good news is that the tools to get it done is there - the bad news is
> that you have to put them together to meet your specific needs (this could
> also be good news since it means that there is a job to do!)

Thanks for the analysis.  I don't want to create work for anyone, as I
don't have requirements yet.

In other light-weight concurrency solutions I've seen, such as
stackless Python, it's straight-forward to serialize processes.  I was
afraid I had overlooked something in Erlang.