dynamic code replacement

[Ulf Wiger]

Mark NG wrote:
> 
> G'day !
> 
> I was wondering if there are currently any know problems or issues or gotchas
> with dynamic code replacement under Erlang.
> 
> thanks,
> mark

Not really any issues in the sense that it wouldn't work
Dynamic code replacement can be about as easy or complex as you
want/need to make it. The easiest part is simply loading the module. For
library code, this is all that's needed.

Torbjorn Tornkvist wrote:
> Well, in the case where you are running a server. Make sure that
> you make a module prefixed recursive call to the top loop.
> Example:
> 
> loop(Data) ->
>    receive
>       X ->
>          NewData = do_stuff(Data,X),
>          ?MODULE:loop(NewData)
>    end.

If your new version has a different representation of Data, this will
not work. For this eventuality, OTP provides a framework for performing
synchronized code change with hooks for transformation of internal
state.

A couple of pointers:

- If you want to learn about OTP's system messages
  http://www.erlang.org/doc/doc/index.html
  (Click on "Design Principles")

- If you want to learn about OTP's release handling:
  http://www.erlang.org/doc/doc/lib/sasl-1.6.3/doc/index.html
  (see the User's Guide.)

/Uffe
-- 
Ulf Wiger, Chief Designer AXD 301     <ulf.wiger@REDACTED>
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