#Instructions to demo distributed Elixir capabilities

#start 3 terminal windows

# start 3 Elixir shells with naming the nodes node_a, node_b, node_c

iex --sname node_a
iex --sname node_b
iex --sname node_c

#you will have 3 Elixir nodes named "node_a@vbox"
#the "vbox" can be different in your enviroment, it depends on the hostname

#check none of the ELixir runtime connect to each other yet
#with following function on either of 

Node.list

#the output is a empty list -> []

#in the next two steps connect "node_a" to "node_b" and "node_c"
#calling 

:net_kernel.connect :"node_b@vbox"
:net_kernel.connect :"node_c@vbox"

#explain and show that now all 3 nodes are connected and they are in full mesh
#on "node_c" issue the following

Node.list

#it should return : [:node_a@vbox, :node_b@vbox]

#now we will send a message from node_a to node_b

#first we register the shell process on node_b with 

Process.register(self(), :shell)

#then a receive block should be typed into node_b shell 

receive do
{msg, othershell}-> IO.puts msg
send(othershell, "Hey") 
end

#this will wait until a node_a sends a message in the form of {msg, pid} form
#on node_a call the following

Process.send({:shell, :"node_b@vbox"}, {"Hello", self()}, [:noconnect])

#on node_b the shell will print "Hello", show it
#on node_a call the following

flush

#the shell will print the "answer" to "Hello" -> "Hey"
# explain that sending back the answer is somewhat simpler than first message
# because the shell on node_b knows the pid of the shell on node_a

#with the following we can call a function on another node

:rpc.call :"node_a@vbox", Node, :list, []

#it will return: [:node_a@vbox, :node_c@vbox] 
#explain that node_a is in the list because the function was executed on node_b

#issue the following function on node_a
Node.monitor :"node_b@vbox", true

#then quit from Elixir shell on node_b with pressing Ctrl+c twice
# call flush on node_a

flush

#it will print {:nodedown, :node_b@vbox}
# explain that message above is because node_a monitored node_b 
# and node_b went down