supervisor_bridge

1996 2011 Ericsson AB, All Rights Reserved The contents of this file are subject to the Erlang Public License, Version 1.1, (the "License"); you may not use this file except in compliance with the License. You should have received a copy of the Erlang Public License along with this software. If not, it can be retrieved online at http://www.erlang.org/. Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. The Initial Developer of the Original Code is Ericsson AB. supervisor_bridge

supervisor_bridge Generic Supervisor Bridge Behaviour.

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.

start_link(Module, Args) -> Result start_link(SupBridgeName, Module, Args) -> Result Create a supervisor bridge process. 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.

Module:init(Args) -> Result Initialize process and start subsystem. 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 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) Clean up and stop subsystem. 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.