supervisor_bridge
MODULE
MODULE SUMMARY
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 information.
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:
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,Errorr} where Error is a term with information about the error, and the supervisor_bridge terminates with reason Error.
CALLBACK FUNCTIONS
The following functions should be exported from a supervisor_bridge callback module.
EXPORTS
Types:
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 supervisor_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:
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.