supervisor_bridge(3erl) Erlang Module Definition supervisor_bridge(3erl)
NAME
supervisor_bridge - Generic supervisor bridge behavior.
DESCRIPTION
This behavior module provides a supervisor bridge, a process that con-
nects a subsystem not designed according to the OTP design principles
to a supervision tree. The supervisor bridge sits between a supervisor
and the subsystem. It behaves like a real supervisor to its own super-
visor, but has a different interface than a real supervisor to the sub-
system. For more information, see Supervisor Behaviour in OTP Design
Principles.
A supervisor bridge assumes the functions for starting and stopping the
subsystem to be located in a callback module exporting a predefined set
of functions.
The sys(3erl) module can be used for debugging a supervisor bridge.
Unless otherwise stated, all functions in this module fail if the spec-
ified supervisor bridge does not exist or if bad arguments are speci-
fied.
EXPORTS
start_link(Module, Args) -> Result
start_link(SupBridgeName, Module, Args) -> Result
Types:
SupBridgeName = {local, Name} | {global, Name}
Name = atom()
Module = module()
Args = term()
Result = {ok, Pid} | ignore | {error, Error}
Error = {already_started, Pid} | term()
Pid = pid()
Creates a supervisor bridge process, linked to the calling
process, which calls Module:init/1 to start the subsystem. To
ensure a synchronized startup procedure, this function does not
return until Module:init/1 has returned.
* If SupBridgeName={local,Name}, the supervisor bridge is reg-
istered locally as Name using register/2.
* If SupBridgeName={global,Name}, the supervisor bridge is
registered globally as Name using global:register_name/2.
* If SupBridgeName={via,Module,Name}, the supervisor bridge is
registered as Name using a registry represented by Module.
The Module callback is to export functions register_name/2,
unregister_name/1, and send/2, which are to behave like the
corresponding functions in global. Thus, {via,global,Global-
Name} is a valid reference.
If no name is provided, the supervisor bridge is not registered.
Module is the name of the callback module.
Args is an arbitrary term that is passed as the argument to Mod-
ule:init/1.
* If the supervisor bridge and the subsystem are successfully
started, the function returns {ok,Pid}, where Pid is is the
pid of the supervisor bridge.
* If there already exists a process with the specified Sup-
BridgeName, the function returns {error,{al-
ready_started,Pid}}, where Pid is the pid of that process.
* If Module:init/1 returns ignore, this function returns ig-
nore as well and the supervisor bridge terminates with rea-
son normal.
* If Module:init/1 fails or returns an error tuple or an in-
correct value, this function returns {error,Errorr}, where
Error is a term with information about the error, and the
supervisor bridge terminates with reason Error.
CALLBACK FUNCTIONS
The following functions must be exported from a supervisor_bridge call-
back module.
EXPORTS
Module:init(Args) -> Result
Types:
Args = term()
Result = {ok,Pid,State} | ignore | {error,Error}
Pid = pid()
State = term()
Error = term()
Whenever a supervisor bridge is started using start_link/2,3,
this function is called by the new process to start the subsys-
tem and initialize.
Args is the Args argument provided to the start function.
The function is to return {ok,Pid,State}, where Pid is the pid
of the main process in the subsystem and State is any term.
If later Pid terminates with a reason Reason, the supervisor
bridge terminates with reason Reason as well. If later the su-
pervisor bridge is stopped by its supervisor with reason Reason,
it calls Module:terminate(Reason,State) to terminate.
If the initialization fails, the function is to return {er-
ror,Error}, where Error is any term, or ignore.
Module:terminate(Reason, State)
Types:
Reason = shutdown | term()
State = term()
This function is called by the supervisor bridge when it is
about to terminate. It is to be the opposite of Module:init/1
and stop the subsystem and do any necessary cleaning up. The re-
turn value is ignored.
Reason is shutdown if the supervisor bridge is terminated by its
supervisor. If the supervisor bridge terminates because a a
linked process (apart from the main process of the subsystem)
has terminated with reason Term, then Reason becomes Term.
State is taken from the return value of Module:init/1.
SEE ALSO
supervisor(3erl), sys(3erl)
Ericsson AB stdlib 3.13 supervisor_bridge(3erl)