# Module Netplex_cenv

    module Netplex_cenv: sig .. end

Container environment

Some helper functions to explore the environment from a container. Most of the following functions must be called from a container context, i.e. from a process or thread that acts as container, otherwise the exception `Not_in_container_thread` is raised. There are also some functions that can be called from controller context for convenience.

Thread safety: Full. The functions in this module can be called from any thread.

    exception Not_in_container_thread

Raised when the caller's thread is not a container thread

## Logging

Logging functions can be invoked from both container and controller contexts.

    val log : Netplex_types.level -> string -> unit

Writes a log message

    val logf : Netplex_types.level -> ('a, unit, string, unit) Pervasives.format4 -> 'a

Writes a log message like `printf`

    val report_connection_string : Unix.file_descr -> string -> string

Output a log line for the `netplex.connections` admin message. The string is the detail to report.

## Timer

Timer functions can only be invoked from container contexts. More documentation is available in Running timers in containers.

    type timer

A timer

    val create_timer : (timer -> bool) -> float -> timer

`create_timer f tmo`: Creates a timer with timeout value `tmo`: In `tmo` seconds `f` is called, and if this function returns `true`, the timer remains active, and another round of timing is arranged. If the functions returns `false` or raises an exception, the timer is stopped.

Timers are also stopped on container shutdown.

Timers are attached to the container event system, and run only if this event system runs. Also note that `f` is always called from the main thread of the container.

    val cancel_timer : timer -> unit

Cancels the timer: The callback function is not called any longer

    val cancel_all_timers : unit -> unit

Cancels all active timers

    val timer_id : timer -> int

Returns an ID, e.g. useful for debugging

## Container variables

Container variables exist once per container. Primary access is done via the `var` and `set_var` methods of the container class. The following functions are often more convenient, however.

These functions can only be invoked from container contexts.

More documentation: Container variables

    exception Container_variable_not_found of string

The variable does not exist

    exception Container_variable_type_mismatch of string

The (dynamically typed) variable has the wrong type

    val int_var : string -> int

    val string_var : string -> string

    val float_var : string -> float

    val bool_var : string -> bool

Access a variable with simple type. May raise `Container_variable_not_found` or `Container_variable_type_mismatch`

    val set_int_var : string -> int -> unit

    val set_string_var : string -> string -> unit

    val set_float_var : string -> float -> unit

    val set_bool_var : string -> bool -> unit

Set a variable with simple type

    val make_var_type : ('a -> Netplex_types.encap) ->
           (Netplex_types.encap -> 'a) -> (string -> 'a) * (string -> 'a -> unit)

Create get and set functions for any (monomorphic) type. For example, to create such function for a type `foo`, do

              module E = Netplex_encap.Make_encap(struct type t = foo end)
              let (get, set) =
                make_var_type E.wrap E.unwrap

Read on for using functors to create `get` and `set`.

    module type TYPE = sig .. end

Just a (monomorphic) type `t`

    module type VAR_TYPE = sig .. end

A (monomorphic) type `t` with two functions `get` and `set` accessing the container variables

    module Make_var_type: functor (T : TYPE) -> VAR_TYPE  with type t = T.t

Creates `get` and `set` like `make_var_type`.

## System control

System control functions can be invoked from both container and controller contexts.

    val system_shutdown : unit -> unit

Initiates a system shutdown (like the `shutdown` method of the controller)

    val system_restart : unit -> unit

Initiates a system restart (like the `restart` method of the controller)

## Inter-Container Communication

These functions can only be invoked from container contexts, except `send_message`.

    val send_message : string -> string -> string array -> unit

`send_message service_pattern msg_name msg_arguments`: Sends a message to all services and message receivers matching `service_pattern`. The pattern may include the wildcard `*`.

See the `Netplex_types.controller.send_message` method for the notification guarantees.

This function can be invoked from both container and controller contexts.

    val lookup : string -> string -> string option

`lookup service_name protocol_name` tries to find a Unix domain socket for the service and returns it.

On Win32, the returned path refers to a file describing the IPC mechanism. Use `Netplex_sockserv.any_file_client_connector` to convert the path into an RPC connector.

    val lookup_container_sockets : string -> string -> string array

`lookup_container_sockets service_name protocol_name`: returns the Unix Domain paths of all container sockets for this service and protocol. These are the sockets declared with address type "container" in the config file.

On Win32, the returned paths refer to files describing the IPC mechanism. Use `Netplex_sockserv.any_file_client_connector` to convert the paths into RPC connectors.

Container sockets are explained here: Sending messages to individual containers

## Direct container and admin interface access

    val self_cont : unit -> Netplex_types.container

Returns the container running the code of the caller, or raise `Not_in_container_thread` if called from outside a container context.

    val self_obj : unit ->
           [ `Container of Netplex_types.container
           | `Controller of Netplex_types.controller ]

Returns the container or the controller running the code of the caller, or raise `Not_found` if called from neither a container not a controller thread.

    val current_sys_id : unit -> [ `Process of int | `Thread of int ]

Returns the system-dependent thread identifier of the caller (which must be in container or controller context)

    val admin_connector : unit -> Rpc_client.mode2

Determines the admin socket of the controller, and returns an RPC client connector suitable for connecting with the admin interface of the controller. For instance to initiate a system shutdown from the context of a container:

             let conn = Netplex_cenv.admin_connector() in
             let client = Netplex_ctrl_clnt.Admin.V2.create_client2 conn in
             Netplex_ctrl_clnt.Admin.V2.system_shutdown client ();
             Rpc_client.shut_down client

Note that the admin interface is going to evolve, and it is advisable to avoid admin calls whenever possible.

This function must be called from container context.

    val run_in_controller_context : Netplex_types.controller -> (unit -> unit) -> unit

`run_in_controller_context ctrl f`: Arranges that `f()` is executed in the context of the controller. This is only possible for multi-threading but not for multi-processing style! For programs using multi-processing, see `Netplex_cenv.Make_lever` for a workaround.

This function can be called from any thread. The function `f` is executed by pushing it onto the event queue, and calling it when the pushed event is reached. This is usually a safe point for many kinds of operations, but if controller methods are invoked the details are left unspecified.

For example, this allows it to start helper threads via `Netplex_kit.add_helper_service` at any time.

An example can be found here: Levers - calling controller functions from containers

    val run_in_container_context : Netplex_types.container -> (unit -> unit) -> unit

`run_in_container_context cont f`: Arranges that `f()` is executed in the context of the container `cont`. This is only possible for multi-threading but not for multi-processing style!

This function can be called from any thread. The function `f` is executed by pushing it onto the event queue, and calling it when the pushed event is reached. This is usually a safe point for many kinds of operations, but if container method are invoked the details are left unspecified.

There is no guarantee that `f` is called anytime soon - if the container is busy with something else than with the event queue the execution will be blocked until these other activities are over.

Levers are a way to send messages to the controller, and to effectively run functions there that were previously registered.

More documentation: Levers - calling controller functions from containers

    module type FUN_TYPE = sig .. end

Abstraction for function types `s->t`

    module type LEVER = sig .. end

    module Make_lever: functor (T : FUN_TYPE) -> LEVER  with type s=T.s and type r=T.r

Creates a `LEVER` module from a function type as specified in `FUN_TYPE`

## Persistent kernel objects

    val pmanage : unit -> Netsys_pmanage.pmanage

Access the manager for persistent kernel objects with limited lifetime. Among these objects there are shared memory objects, and named semaphores. These objects can usually be deleted when the program finishes (or crashes), but this is not done automatically because of kernel persistency.

See Deleting persistent kernel objects for more information.

# Debugging

    module Debug: sig .. end