[erlang-questions] Problem attaching a shell to an Erlang node started through SSH

Ivan Uemlianin <>
Sat Jul 7 12:31:43 CEST 2012


Dear André

Sorry I made a typo in my email (never try to be helpful before 
breakfast;).  I should have written:

 >> - this function calls an *init* script instead of calling the
 >> release start directly.

e.g.:

     sudo("webapp start")

Then the shell script "webapp" calls start functions for the python app 
and the erlang app (i.e., "/path/to/erlangapp/rel/eappnode/bin/eappnode 
start").

 > :~/test_project/rel/mynode/bin$ sudo ./mynode attach
 > ...

I didn't know about attach!  I've just verified I can ssh onto the 
remote machine and attach to the node.

Why is sshing onto the remote machine and attaching better than running 
an erlang shell on your local machine and connecting to the remote 
machine from there?

Thanks

Ivan


On 06/07/2012 09:17, André Graf wrote:
> Hi Ivan,
>
> Running EUnit works. I am pretty sure the problem is somehow related
> with the runner script generated by Rebar (which I haven't changed).
> I tried both sudo and run. I forgot to mention that you must disable
> fabric pty when starting the node through the runner script otherwise
> the start call succeeds but no node (and also no logs) are generated.
>
> Symptoms are difficult to describe. The resulting shell looks like that:
> :~/test_project/rel/mynode/bin$ sudo ./mynode attach
> Attaching to /tmp//home/user/test_project/rel/mynode/erlang.pipe.3 (^D to exit)
>
> ^R
>
> So I won't get the normal Erlang shell prompt, I can run some Erlang
> commands though, but I don't have any tab-completion.
> Ctrl-D will properly exit, Ctrl-G is not giving me the User switch
> command, Ctrl-C gives the proper Break menu.
>
> Funny here, If I don't use sudo for the attach I get a "Node is not
> running!" although the node was started without using sudo, but this
> problem also appears if I start the node directly on the server
> without going through SSH.
>
> Cheers,
> André
>
>
>
>
>
>
> On 6 July 2012 07:27, Ivan Uemlianin <> wrote:
>> Dear André
>>
>> This is what we're doing (see my recent email) and the erlang is working
>> fine. I'll be at the office this afternoon to check properly but here are a
>> few differences:
>>
>> - our fab script uses sudo() instead of run();
>> - this function calls an unit script instead of calling the release start
>> directly.
>>
>>> However, attaching a shell to the
>>> node triggers a strange
>>> behavior, the shell is available but
>>> unusable.
>>
>> What are the symptoms?
>>
>> Best wishes
>>
>> Ivan
>>
>>
>> Sent from my iPhone
>>
>> On 5 Jul 2012, at 23:27, André Graf <> wrote:
>>
>> Hello,
>>
>> I am working on a small library that uses Python Fabric together with
>> Rebar deploying of Erlang applications. Fabric provides a scriptable
>> (it's Python) abstraction over SSH.
>> While I am able to deploy and upgrade new releases through such a
>> fabric script I struggle with a simple Erlang node startup.
>>
>> A fabric call e.g. run("/path/to/my/release/bin/myproject start")
>> invokes following SSH command
>> ssh  "/bin/bash -l -c '/path/to/my/release/bin/myproject start'"
>>
>> This starts the node and I can use the remote shell to operate on the
>> node. However, attaching a shell to the node triggers a strange
>> behavior, the shell is available but unusable. It seems the startup
>> through SSH has somehow confused the involved pipes.
>>
>> Do you have any hints on that? I am using rebar 2.0.0 R15B
>> 20120625_185716 git 2.0.0-45-gc41fda6.
>>
>> Cheers,
>> Andre
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>>
>>
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-- 
============================================================
Ivan A. Uemlianin PhD
Llaisdy
Speech Technology Research and Development

                     
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