Wed Aug 28 11:58:47 CEST 2002
Richard Carlsson wrote:
> - Is it necessary to be able to exchange any single module?
> (E.g., if your application consists of a number of modules,
> do you always replace all these modules anyway?)
Installing simple patches by loading new modules in a live system has been
used at both Bluetail and Cellpoint. (This can also be used to impress
> - Could code migration be limited to specific functions, or
> is it necessary to be able to switch to a new version at all
> "remote" calls. (E.g., one could imagine a new declaration
> for specifying only certain functions as code update points.)
> - Do you always use the OTP release handler or similar to
> do code updates, or do you do it by hand, or with your own
> in-house tools, etc? Do you find it simple as it is today,
> or is code update so difficult that you try to avoid it?
Bluetail used release handlers IIRC, Cellpoint does not.
> - How much of a problem are circular module dependencies in
I believe OTP is full of circular module dependences. (Since Erlang handles
this without complaint, most people probably don't, however, consider it a
> - Is the flexibility of being able to change any module at any
> time (even in production code) worth more to you than the
> speed of the code?
> - When you make a (remote) call that is expected to switch
> to new code whenever it has been loaded, could you guarantee
> that the call stack is empty at that point, i.e., you will
> not return to the old code, nor to the code that called it?
> (If so, the code purging stage would not have to scan the
> stacks of processes to find out if they must be killed.)
> This pretty much equals saying that code change always starts
> a fresh process, but keeps the old Pid.
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