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supervisor_bridge(3erl) Erlang Module Definition supervisor_bridge(3erl) NAME
supervisor_bridge - Generic Supervisor Bridge Behaviour. DESCRIPTION
A behaviour module for implementing a supervisor_bridge, a process which connects 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 supervisor, but has a different interface than a real supervisor to the subsystem. Refer to OTP Design Principles for more informa- tion. A supervisor_bridge assumes the functions for starting and stopping the subsystem to be located in a callback module exporting a pre- defined set of functions. The sys module can be used for debugging a supervisor_bridge. Unless otherwise stated, all functions in this module will fail if the specified supervisor_bridge does not exist or if bad arguments are given. EXPORTS
start_link(Module, Args) -> Result start_link(SupBridgeName, Module, Args) -> Result Types SupBridgeName = {local,Name} | {global,Name} Name = atom() Module = atom() Args = term() Result = {ok,Pid} | ignore | {error,Error} Pid = pid() Error = {already_started,Pid} | term() Creates a supervisor_bridge process, linked to the calling process, which calls Module:init/1 to start the subsystem. To ensure a synchronized start-up procedure, this function does not return until Module:init/1 has returned. If SupBridgeName={local,Name} the supervisor_bridge is registered locally as Name using register/2 . If SupBridgeName={global,Name} the supervisor_bridge is registered globally as Name using global:register_name/2 . If no name is provided, the supervisor_bridge is not registered. If there already exists a process with the specified SupBridgeName the function returns {error,{already_started,Pid}} , where Pid is the pid of that process. Module is the name of the callback module. Args is an arbitrary term which is passed as the argument to Module: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 Module:init/1 returns ignore , this function returns ignore as well and the supervisor_bridge terminates with reason normal . If Module:init/1 fails or returns an error tuple or an incorrect value, this function returns {error,Term} where Term is a term with information about the error, and the supervisor_bridge terminates with reason Term . CALLBACK FUNCTIONS
The following functions should be exported from a supervisor_bridge callback 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 supervisor_bridge:start_link/2,3 , this function is called by the new process to start the subsystem and initialize. Args is the Args argument provided to the start function. The function should 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 will terminate with reason Reason as well. If later the super- visor_bridge is stopped by its supervisor with reason Reason , it will call Module:terminate(Reason,State) to terminate. If something goes wrong during the initialization the function should return {error,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 should be the opposite of Module:init/1 and stop the subsystem and do any necessary cleaning up. The return 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 , Reason will be Term . State is taken from the return value of Module:init/1 . SEE ALSO
supervisor(3erl) , sys(3erl) Ericsson AB stdlib 1.17.3 supervisor_bridge(3erl)
