Erlang: ways to specify the server in gen_server:call
You can gen_server:call in a bunch of different ways.
If you have a process ID:
gen_server:call(Pid, Req). % local by pid
If it’s registered locally:
gen_server:call(Name, Req). % local by name -- uses whereis(Name)
gen_server:call({local, Name}, Req). % local by name -- uses whereis(Name)
Note that {local, Name} is undocumented – it’s not listed under
server_ref() and might not always be supported.
If it’s registered in global:
gen_server:call({global, Name}, Req). % global by name -- uses global:whereis_name(Name)
If it’s registered in some other process registry:
gen_server:call({via, Registry, Name}, Req). % via by name -- uses Registry:whereis_name(Name)
global uses the same interface as via:
gen_server:call({via, global, Name}, Req). % global uses the same API as user-defined registries
You can also call named processes on remote nodes (or on the local node):
gen_server:call({Name, LocalNode}, Req). % local by name -- uses whereis(Name)
gen_server:call({Name, RemoteNode}, Req). % remote by name -- uses erlang:send({Name, RemoteNode}, ...)