Rails - Mar 2006 - Run command via SSH session displaying results via AJAX

I am trying to create a web app that allows me to invoke a command on 
another server via an SSH session.  I am currently doing this as 
follows:

1) User is presented with a form to enter server, command, username and 
password.
2) User clicks "Run" and form is submitted to the
"run_command" action.
3) The "run_command" action initiates an SSH session using net-ssh and
registers callbacks with the SSH session to append any command output to 
the web session[:command_output].  Thus, session[:command_output] grows 
until all results (stdout and stderr) are accumulated.
4) The "run_command" redirects to the results page which then renders 
the web session[:command_output] which is viewed by the user.

This is working fine, but what I really want to do is alter step 3 so 
that the SSH session accumulates the results but the results page is 
rendered before the SSH session is complete.  Then in step 4 I could use 
AJAX to periodically update the command output results as they come in 
instead of waiting for them all to come in before displaying them.

In order to do this it seems I would need threading and that introduces 
complexities and prefer to not deal with.

Another possibility I thought of was to somehow have the results page be 
the one that makes an AJAX call to the "run_command" action that will 
initiate the SSH session, and have the SSH session callbacks send the 
data to the browser realtime instead of appending to the web session 
variable.  I''ve done something similar in Python with Twisted and 
Nevow/LivePage before, but am unsure how to do so with Rails.

Does anyone have any thoughts or advice on how I might solve this 
problem?

Thanks,
Justin

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Posted via http://www.ruby-forum.com/.

What id you had one action that executed the command.  This action  
would do steps 1-3 below.  Then have some AJAX on the view that  
simply replaces the contents of the display div with the current  
value of session[:command_output].  Since the session will persist  
between calls, you will still have the entire output in the session.

Not sure if I''m on the right track here, but those are my initial  
thoughts.

-Derrick Spell

On Mar 8, 2006, at 11:52 AM, Justin Johnson wrote:
> I am trying to create a web app that allows me to invoke a command on
> another server via an SSH session.  I am currently doing this as
> follows:
>
> 1) User is presented with a form to enter server, command, username  
> and
> password.
> 2) User clicks "Run" and form is submitted to the
"run_command"
> action.
> 3) The "run_command" action initiates an SSH session using
net-ssh and
> registers callbacks with the SSH session to append any command  
> output to
> the web session[:command_output].  Thus, session[:command_output]  
> grows
> until all results (stdout and stderr) are accumulated.
> 4) The "run_command" redirects to the results page which then
renders
> the web session[:command_output] which is viewed by the user.
>
> This is working fine, but what I really want to do is alter step 3 so
> that the SSH session accumulates the results but the results page is
> rendered before the SSH session is complete.  Then in step 4 I  
> could use
> AJAX to periodically update the command output results as they come in
> instead of waiting for them all to come in before displaying them.
>
> In order to do this it seems I would need threading and that  
> introduces
> complexities and prefer to not deal with.
>
> Another possibility I thought of was to somehow have the results  
> page be
> the one that makes an AJAX call to the "run_command" action that
will
> initiate the SSH session, and have the SSH session callbacks send the
> data to the browser realtime instead of appending to the web session
> variable.  I''ve done something similar in Python with Twisted and
> Nevow/LivePage before, but am unsure how to do so with Rails.
>
> Does anyone have any thoughts or advice on how I might solve this
> problem?
>
> Thanks,
> Justin
>
> -- 
> Posted via http://www.ruby-forum.com/.
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

Derrick Spell wrote:
> What id you had one action that executed the command.  This action
> would do steps 1-3 below.  Then have some AJAX on the view that
> simply replaces the contents of the display div with the current
> value of session[:command_output].  Since the session will persist
> between calls, you will still have the entire output in the session.
That is basically what I am talking about, except I''m trying to find a 
way to start the SSH session and have it run in the background (another 
thread?) and send its results to the page via AJAX calls.
> Not sure if I''m on the right track here, but those are my initial
> thoughts.
> 
> -Derrick Spell

-- 
Posted via http://www.ruby-forum.com/.

Oh I think I know what you''re saying now.

If I have the form submitted via AJAX, then I don''t have to wait for
the
next page to be displayed (the one that previously wasn''t being
rendered
until the SSH session was done).  So once they click the button to 
submit, an AJAX call is made to run_command which appends output to the 
session variable.  In addition, clicking the buttom would have to start 
a periodic refresh to display the contents of the session variable, thus 
displaying the output as it accumulates.

Justin Johnson wrote:
> Derrick Spell wrote:
>> What id you had one action that executed the command.  This action
>> would do steps 1-3 below.  Then have some AJAX on the view that
>> simply replaces the contents of the display div with the current
>> value of session[:command_output].  Since the session will persist
>> between calls, you will still have the entire output in the session.
> 
> That is basically what I am talking about, except I''m trying to
find a
> way to start the SSH session and have it run in the background (another 
> thread?) and send its results to the page via AJAX calls.
> 
>> Not sure if I''m on the right track here, but those are my
initial
>> thoughts.
>> 
>> -Derrick Spell

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