Implement session manager

[oubiwann]

The shell manager needs to create an LFE shell for each "user" (client IP address). The following capabilities would be needed:

• The ability to dynamically start a new "shell" process (maybe not a real LFE shell ...) per "user"
• A means of tracking how long a user has been active / idle
• Add a long-running processes that regularly checks for stale user sessions  #19 - The ability to prune idle processes (stale sessions)
• A way of recording the number of any "bad actor" calls made from any given IP address
• A way of recording the number of connection requests per second/minute/hour/etc made by any given IP address
• Putting "shell creation" requests into a "queue" with bad IP addresses getting put into exponentially longer waiting times before connection after recorded bad actions
• Watch for errors in "shells" (sessions) and kill processes with errors, transparently initiating a session re-creation the next time that IP address asks for an LFE code eval
• Track overall manager runtime and the ability to request self-restart after a fixed time

Note: the need for this might be obviated by the option proposed in ticket #14.

[rvirding]

These three issues, #8 #9 and #14, are really three sides of the same problem so I will write once and copy and then we will see where the discussion goes.

• It would be quite easy to open the LFE shell and provide externally callable functions to process commands. run_string and run_script almost do that today.
• You would then write a new top-loop using these functions.
• This would not solve the problem of input/output when processing the commands, they by default send to/read from standard_io.

An easier way might then be to use the existing shell but to reset where the shell's, and the processes it starts, standard_io to control input/output. You then automatically handle all io in the commands. This is actually very easy to do, an example*:

http://www.geekherocomic.com/2008/11/12/real-programmers-dont-write-documentation/

This can also make the shell manager easier. The real question is then how we want to interface the "shell".

• This is also a good example of how versatile the io system really is. :-)