NAME

       supervisor_bridge - Generic supervisor bridge behavior.

DESCRIPTION

       This  behavior  module  provides  a  supervisor  bridge, a process that 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.  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 specified supervisor  bridge  does  not
       exist or if bad arguments are specified.

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  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  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,GlobalName} 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 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 there already exists a process with  the  specified  SupBridgeName,  the  function  returns
                  {error,{already_started,Pid}}, where Pid is the pid of that process.

                * 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 must 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 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  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 supervisor 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 {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 is to 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, then Reason becomes Term.

              State is taken from the return value of Module:init/1.

SEE ALSO

       supervisor(3erl), sys(3erl)

Ericsson AB                                       stdlib 3.4.3                           supervisor_bridge(3erl)