How do I handle the death of another node in Erlang?

Question

I have two nodes that are connected to each other, where one of them is the server. The server would like to know if the client dies. I did something like this:

link(Client).

In the server process, and when I did that I receive a exception error: noconnection and then the server dies, when the client dies. I would just like to know if the client dies, I do not want the server do die, how do I handle the death message?

Answer 1

If you have two erlang nodes and want to take some actions in case if one node goes down (or network connection is lost) you possible want to use erlang:monitor_node/2,3 functions:

(n1@myhost)1> erlang:monitor_node('n2@myhost', true).
true

then if 'n2@myhost' node goes down your process will receive message:

(n1@myhost)2> flush().
Shell got {nodedown,n2@myhost}

(note, I did that from erlang shell, that is why I may call flush/0 to see what is in the mailbox of the shell process)

If you interested in certain process, on the second node you may use erlang:monitor/2

(n1@myhost)3> Ref = erlang:monitor(process, {'n2@myhost', some_registered_name}).
#Ref<0.0.0.117>

from now you will receive a message if some_registered_name goes down and you can take an action.

Also you may be interested in how to write distributed applications

Answer 2

To have unidirectional supervision, you should use monitors. Then your server will receive a message if the client dies.