unikernel/duniverse/ocaml-caqti/caqti/lib-platform/pool.mli

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+(* Copyright (C) 2014--2023  Petter A. Urkedal <paurkedal@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version, with the LGPL-3.0 Linking Exception.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * and the LGPL-3.0 Linking Exception along with this library.  If not, see
+ * <http://www.gnu.org/licenses/> and <https://spdx.org>, respectively.
+ *)
+
+(** Internal resource pool implementation. *)
+
+(** Scheduling taks in the future. *)
+module type ALARM = sig
+  type switch
+  type stdenv
+
+  type t
+  (** A handle for cancelling the alarm if supported. *)
+
+  val schedule :
+    sw: switch ->
+    stdenv: stdenv ->
+    Mtime.t -> (unit -> unit) -> t
+  (** If supported, [schedule ~sw ~stdenv time f] schedules [f] to be run
+      at [time] and returns a handle which can be used to {!unschedule} it.  The
+      caqti-blocking implementation does nothing.  The pool implementation using
+      it makes additional opportunistic calls to the handler.  This function
+      must insert a yield before running the function even if the delay is
+      non-positive. *)
+
+  val unschedule : t -> unit
+  (** Cancels the alarm if supported. This is only used for early clean-up, so
+      the implementation may choose to let it time out instead. *)
+end
+
+module type S = sig
+  type switch
+  type stdenv
+
+  include Caqti_pool_sig.S
+
+  val create :
+    ?config: Caqti_pool_config.t ->
+    ?check: ('a -> (bool -> unit) -> unit) ->
+    ?validate: ('a -> bool fiber) ->
+    ?log_src: Logs.Src.t ->
+    sw: switch ->
+    stdenv: stdenv ->
+    (unit -> ('a, 'e) result fiber) -> ('a -> unit fiber) ->
+    ('a, 'e) t
+  (** {b Internal:} [create alloc free] is a pool of resources allocated by
+      [alloc] and freed by [free]. This is primarily intended for implementing
+      the [connect_pool] functions.
+
+      @param max_size
+        The maximum number of allocated resources.
+
+      @param max_idle_size
+        The maximum number of resources to pool for later use. Defaults to
+        [max_size].
+
+      @param max_use_count
+        The maximum number of times to use a connection, or [None] for no limit.
+
+      @param check
+        A function used to check a resource after use.
+
+      @param validate
+        A function to check before use that a resource is still valid. *)
+end
+
+module Make
+  (System : System_sig.CORE)
+  (_ : ALARM
+    with type switch := System.Switch.t
+     and type stdenv := System.stdenv) :
+  S with type 'a fiber := 'a System.Fiber.t
+     and type switch := System.Switch.t
+     and type stdenv := System.stdenv
+
+module Make_without_alarm (System : System_sig.CORE) :
+  S with type 'a fiber := 'a System.Fiber.t
+     and type switch := System.Switch.t
+     and type stdenv := System.stdenv