[erlang-questions] Re: Is it safe to use both 5.7.0 and 5.7.1 VMs in one cluster?

Kenneth Lundin <>
Mon Jul 20 21:06:59 CEST 2009


Hi,

On Mon, Jul 20, 2009 at 11:10 AM, mats cronqvist<> wrote:
> Sergey Samokhin <> writes:
>
>> Hello!
>>
>> Is it safe to build an erlang cluster from aplications running under
>> different VMs: say, 5.7.1 and 5.7.0?

Yes it is safe to do that during an upgrade phase but we don't really recommend
running continuously with different versions of the Erlang VM in a
cluster using distributed Erlang.


>
>  Historically, VM's have been backwards compatible with the previous
>  major version. So R14's are pretty much guaranteed to be able to talk
>  to R13's, but might not be able to talk to R12's. (Just an example, I
>  have no idea what R14 will actually do.)
Our strategy has been an still is to be backward compatible with 2
older major versions of
Erlang/OTP when it comes to distributed Erlang. This means that Erlang
nodes based on R13B (01, 02, ...) will be able to work together with
R11B and R12B based nodes and of course R13B works well together with
R13B01, 02, ... as well. When R14B is released
it will be able to work together with nodes based on R12B and R13B.

The interoperability between nodes based on different major versions
of the Erlang VM is a necessity for smooth upgrade of a cluster (one
node at a time) but the intention is
to use this just for the purpose of upgrade and not for normal service
of a cluster.

Regards Kenneth Erlang/OTP, Ericsson

If there are any exceptions to this strategy we will clearly say so in
the release notes.
>
>  mats
>
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