[erlang-questions] Setting compatibility mode via +R

[Michael Loftis]

I don't believe the distribution protocol has changed since like R6 or so.

http://www.erlang.org/doc/apps/erts/erl_dist_protocol.html

On Mon, Jul 15, 2013 at 12:08 PM, Devangana Tarafdar
<devangana@REDACTED> wrote:
> Hello,
>
> I am experimenting with the +R <release number> emulator flag as described
> in the erl  man page ( http://www.erlang.org/doc/man/erl.html) and I am
> confused about when I should be using this and also what happens if I do not
> use this when communicating between 2 nodes from different releases.
>
> "  +R ReleaseNumber
>
> Sets the compatibility mode.
>
> The distribution mechanism is not backwards compatible by default. This
> flags sets the emulator in compatibility mode with an earlier Erlang/OTP
> release ReleaseNumber. The release number must be in the range <current
> release>-2..<current release>. This limits the emulator, making it possible
> for it to communicate with Erlang nodes (as well as C- and Java nodes)
> running that earlier release.
>
> Note: Make sure all nodes (Erlang-, C-, and Java nodes) of a distributed
> Erlang system is of the same Erlang/OTP release, or from two different
> Erlang/OTP releases X and Y, where all Y nodes have compatibility mode X."
>
> This is what I am doing when setting up 2 nodes from release 13B03 and 16B.
> The release numbers difference is greater than 2 so I cannot use the +R flag
> anyway but the nodes have no problems communicating without the flag. I was
> expecting that the nodes would not be able to connect at all but clearly I
> am wrong.
>
> #startup
>
> #first node
> erl -name node_a -setcookie x
> Erlang R13B03 (erts-5.7.4) [source] [64-bit] [smp:4:4] [rq:4]
> [async-threads:0] [hipe] [kernel-poll:false]
>
> Eshell V5.7.4  (abort with ^G)
> (node_a@REDACTED)1> erlang:system_info(otp_release).
> "R13B03"
>
> #second node
> downloads/otp_src_R16B/bin/erl   -name node_b -setcookie x
> Erlang R16B (erts-5.10.1) [source] [64-bit] [smp:4:4] [async-threads:10]
> [kernel-poll:false]
>
> Eshell V5.10.1  (abort with ^G)
> (node_b@REDACTED)1>  erlang:system_info(otp_release).
> "R16B"
>
>
> # subsequent session
> (node_b@REDACTED)3> net_adm:ping('node_a@REDACTED').
> pong
>
>
> (node_a@REDACTED)2> nodes().
> ['node_b@REDACTED']
> (node_a@REDACTED)5> net_kernel:disconnect('node_b@REDACTED').
> true
> (node_a@REDACTED)6> nodes().
> []
> (node_a@REDACTED)7> net_adm:ping('node_b@REDACTED').
> pong
> (node_a@REDACTED)8>
>
>
> Thank you for any help in interpreting this.
>
> Devangana
>
>
>
>
>
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>



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