From 3cf62ca8a11db0d1e89a3f5ed39919c75f447e84 Mon Sep 17 00:00:00 2001
From: Chris Koeritz <fred@gruntose.com>
Date: Tue, 21 Apr 2015 18:21:46 -0400
Subject: [PATCH] cool process trapper keeper, very minimal, just using bash.

---
 scripts/processes/process_manager.sh | 97 ++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 scripts/processes/process_manager.sh

diff --git a/scripts/processes/process_manager.sh b/scripts/processes/process_manager.sh
new file mode 100644
index 00000000..8acab83e
--- /dev/null
+++ b/scripts/processes/process_manager.sh
@@ -0,0 +1,97 @@
+#!/bin/bash
+
+# process manager helper methods for bash.
+#
+# relies on the built-in process management to run a bunch of processes
+# in the background, but will limit total number running to a maximum.
+# demonstration method at the end of the file shows how to use the
+# process managing methods.
+#
+# by chris koeritz
+
+#hmmm: revisions desired someday:
+#  + allow number of max processes to be passed in.
+#  + 
+
+# number of background processes.
+bg_count=0
+
+# maximum number of simultaneous background processes.
+max_bg_procs=20
+
+# number of processes to wait for if we hit the maximum.
+procs_to_await=3
+
+function start_background_action()
+{
+  # launch the commands provided as parms in a subshell.
+  (for i in "${@}"; do eval "$i" ; done)&
+  #echo bg_count pre inc is $bg_count
+  ((bg_count++))
+  #echo bg_count post inc is $bg_count
+}
+
+function take_inventory()
+{
+  start_background_action \
+      'echo "taking inventory..."' \
+      'bash $FEISTY_MEOW_SCRIPTS/core/inventory.sh'
+}
+
+function nechung()
+{
+  start_background_action \
+      'echo "your nechung oracle pronouncement of the moment..."' \
+      '$BINDIR/nechung'
+}
+
+function login_on_xcg()
+{
+  start_background_action \
+      'echo "summing directory output coming up..."' \
+      'perl $FEISTY_MEOW_SCRIPTS/files/summing_dir.pl'
+}
+
+# takes the number of processes to wait for, or just waits for one of them.
+function wait_on_backgrounders()
+{
+  local wait_count="$1"; shift
+
+  target_count=$(($bg_count - $wait_count))
+  if (($target_count < 1)); then target_count=1; fi
+  echo before waiting, count is $bg_count
+  while (($bg_count > $target_count - 1)); do
+    # wait for one job, let bash pick which.
+    wait -n
+    echo bg_count pre dec is $bg_count
+    ((bg_count--))
+    echo bg_count post dec is $bg_count
+  done
+  echo "done waiting, background process count is down to $bg_count."
+}
+
+# happily launches off different actions as background processes.
+launcher_demonstrator()
+{
+  while true; do
+    # pick a thing to do.
+    which=$(($RANDOM % 3))
+#hmmm: not asynch yet!  make it so!
+    case $which in
+      0) take_inventory;;
+      1) nechung;;
+      2) login_on_xcg;;
+    esac
+
+    # we have reached the limit on processes and need to wait for a few, defined by
+    # procs_to_await variable at top.
+    if (($bg_count > $max_bg_procs - 1)); then
+      echo "have reached $max_bg_procs background processes threshold; waiting for $procs_to_await of them to complete."
+      wait_on_backgrounders $procs_to_await
+    fi
+
+  done
+}
+
+launcher_demonstrator;
+
-- 
2.34.1