# Module Netplex_main

    module Netplex_main: sig .. end

Main program for Netplex servers

    type cmdline_config

    val args : ?defaults:cmdline_config ->
           unit ->
           (Stdlib.Arg.key * Stdlib.Arg.spec * Stdlib.Arg.doc) list *
           cmdline_config

`let (opt_list, cmdline_cfg) = args()`: Returns `opt_list` for inclusion in the `Arg.parse` option list. The effects made available by the returned `cmdline_cfg` value.

The defaults (unless overridden by `defaults`): The config file is derived from the name of the executable (by appending `.conf` instead of the current extension). There is no config tree.

`defaults` : The default argument values

    val create : ?config_filename:string ->
           ?config_tree:Netplex_types.config_tree ->
           ?pidfile:string option ->
           ?foreground:bool -> unit -> cmdline_config

Creates the command-line configuration object.

By setting `config_tree` a special configuration can be injected - the file `config_filename` is not loaded in this case (but may still appear in error messages)

    val modify : ?config_filename:string ->
           ?config_tree:Netplex_types.config_tree ->
           ?pidfile:string option ->
           ?foreground:bool ->
           cmdline_config -> cmdline_config

Modifies the command-line configuration object

    val config_filename : cmdline_config -> string

Returns the filename of the configuration file, or the default if it has not been set on the command-line

    val config_filename_opt : cmdline_config -> string option

Returns the filename of the configuration file, or `None` if it has not been set on the command-line

    val config_tree_opt : cmdline_config -> Netplex_types.config_tree option

Returns the tree of the configuration file, or `None` if it has not been set by `create` or `modify`. Note that `args` never sets the config tree.

    val pidfile : cmdline_config -> string option

Returns the location of the PID file (if any)

    val foreground : cmdline_config -> bool

Returns whether the daemon runs in the foreground

    val startup : ?late_initializer:(Netplex_types.config_file ->
                              Netplex_types.controller -> unit) ->
           ?config_parser:(string -> Netplex_types.config_file) ->
           Netplex_types.parallelizer ->
           Netplex_types.logger_factory list ->
           Netplex_types.workload_manager_factory list ->
           Netplex_types.processor_factory list -> cmdline_config -> unit

Establishes a configuration and starts the Netplex daemon.

If a ready-made configuration tree is included in the passed configuration it is taken as the configuration. If otherwise only the name of the config file is available, this file is parsed. Fails with `Netplex_config.Config_error` when an error in the configuration is detected.

The `late_initializer` is called after the Netplex controller has been fully initialized, and before the main event loop is entered. You can perform here further initializations, e.g. starting helper threads.

The `config_parser` is by default `Netplex_config.read_config_file`. You can override it by whatever parser you would like to use. The parser is only used if a configuration tree is unavailable, and the configuration needs to be loaded from a file.

As side-effect, the current logger of the `Netlog` module is set to selected Netplex logger. Note that this setting remains active even after `startup` returns to the caller. Also note that log messages submitted via `Netlog` appear as from component "netplex.other" if they are sent from outside of a container.

It is changed to `/` as working directory (as required for a daemon).

    val run : ?config_parser:(string -> Netplex_types.config_file) ->
           late_initializer:(Netplex_types.config_file -> Netplex_types.controller -> 'a) ->
           extract_result:(Netplex_types.controller -> 'a -> 'b) ->
           Netplex_types.parallelizer ->
           Netplex_types.logger_factory list ->
           Netplex_types.workload_manager_factory list ->
           Netplex_types.processor_factory list -> cmdline_config -> 'b

Similar to `startup`, but this function is tailored for Netplex systems that compute results (e.g. Netmulticore jobs). In this scenario, it is not sufficient to just fire off child processes, but you also want to return a result to the caller once the processes have finished their tasks. One consequence of this is that you cannot daemonize the program - it always runs in the foreground (no matter whether `-fg` is given or not).

`run` expects that the caller passes a function `extract_result`. This function is invoked once the Netplex system is done, and the user can extract the final result from the controller. The result of `extract_result` is also the result of `run`.

At the moment `extract_result` is invoked, the child processes are already terminated. They should have put their result at a place that is in the controller, or can be reached with the help of the controller. The controller functionality is still fully available.

Note that the controller is shut down as soon as `extract_result` returns. Further interactions with the controller are not possible.

The `late_initializer` is now obligatory for typing reasons (so you can get the result of the `late_initializer` from `extract_result`). If you don't need it, just return `()`.

The working directory is left unchanged.

### Tutorial

The typical main program for a `Netplex` server system looks like:

       let my_factories = ...

       let start() =
        let opts, cmdconf = Netplex_main.args() in
        Arg.parse
          opts
          (fun s -> raise(Arg.Bad ("Unknown arg: " ^ s)))
          "usage: protoserver";
        let par = Netplex_mp.mp() in  (* or Netplex_mt.mt() *)
        Netplex_main.startup
          par
          Netplex_log.logger_factories
          Netplex_workload.workload_manager_factories
          my_factories
          cmdconf

       Sys.set_signal Sys.sigpipe Sys.Signal_ignore;
       start()

This main program enables:

- The standard command-line arguments `-conf`, `-pid` and `-fg` are understood
- The configuration file is parsed
- The configuration can refer to all loggers and workload managers coming with Netplex
- The parallelizer is selected: Here, it is multi-processing (Netplex_mp). One could also select multi-threading (Netplex_mt)
- The processors defined by `my_factories` are made available for connection processing