Implement parallel jobs (-j option).

[goals.git] / src / jobs.mli

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+(* Goals parallel jobs.
+ * Copyright (C) 2020 Richard W.M. Jones
+ * Copyright (C) 2020 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *)
+
+(** This module manages parallel jobs.
+
+    Jobs are grouped.  You call [new_group] to create a new
+    group of jobs, initially empty.  Then add jobs to it.  Then
+    wait for all the jobs in the group to complete.
+
+    To submit a job to a group use [start group key f].  [group]
+    is an existing group of jobs to which this is added.  [key] is
+    a key which ensures that two identical jobs cannot be running
+    at the same time (across all groups).  If two or more jobs
+    with the same key are submitted then only one will run and
+    the others will wait until the first finishes, and then another
+    will be picked to run and so on.  Jobs with different keys run
+    freely in parallel, assuming there are enough threads available
+    to run them.
+
+    Goals uses the goal (name + parameters) as the key to
+    ensure you cannot have two jobs running at the same time
+    which would interfere with each other by trying to build
+    the same target.
+
+    To wait for a group of jobs to complete, call [wait group].
+ *)
+
+module type Key = sig
+  type t
+  val compare : t -> t -> int
+  val to_string : t -> string
+end
+
+module type Jobs = sig
+  type key
+  type group
+
+  val new_group : unit -> group
+  (** Create a new empty jobs group. *)
+
+  val start : group -> key -> (unit -> unit) -> unit
+  (** [start group key f] submits a job to run in the background.
+      The [key] ensures that two jobs with the same key cannot run
+      at the same time (across all groups). *)
+
+  val wait : group -> unit
+  (** [wait group] waits for all of the jobs in the group to finish. *)
+end
+
+module Make (K : Key) : Jobs with type key = K.t