From 7ae0325a2d19a6866b599090d89b3706ac213263 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rn-Michael=20Miehe?=
 <40151420+ldericher@users.noreply.github.com>
Date: Thu, 3 Mar 2022 00:05:14 +0100
Subject: [PATCH] externalize schedule randomization

---
 libexec/kiwi-cron/create_schedule    | 30 ++++++----------------------
 libexec/kiwi-cron/randomize_schedule | 25 +++++++++++++++++++++++
 libexec/kiwi-cron/scheduler          | 29 +++++++++++++++++++++------
 3 files changed, 54 insertions(+), 30 deletions(-)
 create mode 100755 libexec/kiwi-cron/randomize_schedule

diff --git a/libexec/kiwi-cron/create_schedule b/libexec/kiwi-cron/create_schedule
index 5a09075..2d31a64 100755
--- a/libexec/kiwi-cron/create_schedule
+++ b/libexec/kiwi-cron/create_schedule
@@ -13,41 +13,23 @@ fi
 # generate valid random schedule values
 # generally, "nighttime" and "weekend" will be preferred.
 
-# shellcheck disable=SC3028 # RANDOM is defined in alpine's /bin/sh
-cs_rand_min=$(( RANDOM % 60 ))
-
-# shellcheck disable=SC3028
-# cs_rand_hour=$(( RANDOM % 24 ))
-cs_rand_hour=$(( (21 + RANDOM % 7) % 24 ))
-
-# shellcheck disable=SC3028
-cs_rand_day=$(( RANDOM % 31 + 1 ))
-
-# shellcheck disable=SC3028
-# cs_rand_weekday=$(( RANDOM % 7 ))
-cs_rand_weekday=$(( (6 + RANDOM % 2) % 7 ))
-
-# shellcheck disable=SC3028
-# cs_rand_month=$(( RANDOM % 12 + 1 ))
-cs_rand_month=$(( RANDOM % 2 + 1 ))
-
 case "${cs_units}" in
   minute)
-    echo "*${cs_every}" "*" "*" "*" "*" "${cs_command}" 
+    echo "*${cs_every} * * * * ${cs_command}" 
     ;;
   hour)
-    echo "${cs_rand_min}" "*${cs_every}" "*" "*" "*" "${cs_command}" 
+    echo "R *${cs_every} * * * ${cs_command}" 
     ;;
   day)
-    echo "${cs_rand_min}" "${cs_rand_hour}" "*${cs_every}" "*" "*" "${cs_command}" 
+    echo "R R *${cs_every} * * ${cs_command}" 
     ;;
   week)
-    echo "${cs_rand_min}" "${cs_rand_hour}" "*" "*" "${cs_rand_weekday}" "${cs_command}" 
+    echo "R R * * R ${cs_command}" 
     ;;
   month)
-    echo "${cs_rand_min}" "${cs_rand_hour}" "${cs_rand_day}" "*${cs_every}" "*" "${cs_command}" 
+    echo "R R R *${cs_every} * ${cs_command}" 
     ;;
   year)
-    echo "${cs_rand_min}" "${cs_rand_hour}" "${cs_rand_day}" "${cs_rand_month}" "*" "${cs_command}" 
+    echo "R R R R * ${cs_command}" 
     ;;
 esac
diff --git a/libexec/kiwi-cron/randomize_schedule b/libexec/kiwi-cron/randomize_schedule
new file mode 100755
index 0000000..c5e938a
--- /dev/null
+++ b/libexec/kiwi-cron/randomize_schedule
@@ -0,0 +1,25 @@
+#!/bin/sh
+
+# shellcheck disable=SC3028 # RANDOM is defined in alpine's /bin/sh
+
+read -r rs_minute rs_hour rs_day rs_month rs_weekday rs_command
+
+[ "${rs_minute}" = "R" ] && \
+  rs_minute=$(( RANDOM % 60 ))
+
+[ "${rs_hour}" = "R" ] && \
+  rs_hour=$(( (21 + RANDOM % 7) % 24 ))   # prefer nighttime
+  # rs_hour=$(( RANDOM % 24 ))            # don't prefer nighttime
+
+[ "${rs_day}" = "R" ] && \
+  rs_day=$(( RANDOM % 28 + 1 ))           # don't mess with February 31st
+
+[ "${rs_month}" = "R" ] && \
+  rs_month=$(( RANDOM % 2 + 1 ))          # prefer January & February
+  # rs_month=$(( RANDOM % 12 + 1 ))       # don't prefer January & February
+
+[ "${rs_weekday}" = "R" ] && \
+  rs_weekday=$(( (6 + RANDOM % 2) % 7 ))  # prefer weekends
+  # rs_weekday=$(( RANDOM % 7 ))          # don't prefer weekends
+
+echo "${rs_minute} ${rs_hour} ${rs_day} ${rs_month} ${rs_weekday} ${rs_command}"
diff --git a/libexec/kiwi-cron/scheduler b/libexec/kiwi-cron/scheduler
index e9b79aa..aca5381 100755
--- a/libexec/kiwi-cron/scheduler
+++ b/libexec/kiwi-cron/scheduler
@@ -1,5 +1,7 @@
 #!/bin/sh
 
+# shellcheck disable=SC3001 # process substitution are defined in alpine's /bin/sh
+
 this_script="$( readlink -f "${0}" )"
 this_dir="${this_script%/*}"
 
@@ -42,7 +44,7 @@ schedule_dirs="$(
 )"
 
 for schedule_dir in ${schedule_dirs}; do
-  # ignore if no files
+  # ignore dirs without files
   if dir_has_no_files "${schedule_dir}"; then
     continue
   fi
@@ -52,7 +54,9 @@ for schedule_dir in ${schedule_dirs}; do
   units="${dir_name%ly}"
   units="$( dir_to_unit "${units}" )"
 
-  "${this_dir}/create_schedule" "1" "${units}" "run-parts '${schedule_dir}'"
+  "${this_dir}/create_schedule" \
+    "1" "${units}" "run-parts '${schedule_dir}'" \
+    | "${this_dir}/randomize_schedule"
 done
 
 # check dirs in "/kiwi-cron/every" directory
@@ -61,16 +65,29 @@ every_schedule_dirs="$(
 )"
 
 for schedule_dir in ${every_schedule_dirs}; do
-  # ignore if no files
+  # ignore dirs without files
   if dir_has_no_files "${schedule_dir}"; then
     continue
   fi
 
   # infer schedule params by directory name
   dir_name="${schedule_dir##*/}"
-  every="$( echo "${dir_name}" | awk -F_ '{print $1}' )"
-  units="$( echo "${dir_name}" | awk -F_ '{print $2}' )"
+  case "${dir_name}" in
+    *_*) # looks like: every/5_minutes
+      read -r every units < \
+        <( echo "${dir_name}" | tr '_' ' ' )
+      ;;
+
+    *) # probably looks like: every/day
+      every="1"
+      units="${dir_name}"
+      ;;
+  esac
+
+  # remove trailing "s" if present
   units="${units%s}"
 
-  "${this_dir}/create_schedule" "${every}" "${units}" "run-parts '${schedule_dir}'"
+  "${this_dir}/create_schedule" \
+    "${every}" "${units}" "run-parts '${schedule_dir}'" \
+    | "${this_dir}/randomize_schedule"
 done