run shepherd via cron

README.md

@@ -29,7 +29,7 @@ A Docker swarm service for automatically updating your services whenever their b
 
 ### Configuration
 
-Shepherd will try to update your services every 5 minutes by default. You can adjust this value using the `SLEEP_TIME` variable.
+Shepherd will try to update your services every 5 minutes by default. You can adjust this value using the `SLEEP_TIME` variable. Alternatively set `CRON_SETTING` to run shepherd at a given time. When `CRON_SETTING` is provided, `SLEEP_TIME` will be ignored.
 
 You can prevent services from being updated by appending them to the `IGNORELIST_SERVICES` variable. This should be a space-separated list of service names.
 

shepherd

@@ -133,7 +133,7 @@ get_registry_password() {
     fi
 }
 
-main() {
+run_main() {
   local sleep_time supports_detach_option supports_registry_auth verbose image_autoclean_limit ignorelist
   local registry_user=""
   local registry_password=""
@@ -181,6 +181,7 @@ main() {
 
   if [[ ${RUN_ONCE_AND_EXIT+x} ]]; then
     update_services "$ignorelist" "$supports_detach_option" "$supports_registry_auth" "$supports_insecure_registry" "$supports_no_resolve_image" "$image_autoclean_limit" "$registry_user" "$registry_password" "$registry_host"
+    logger "Update finished." "true"
   else
     while true; do
       update_services "$ignorelist" "$supports_detach_option" "$supports_registry_auth" "$supports_insecure_registry" "$supports_no_resolve_image" "$image_autoclean_limit" "$registry_user" "$registry_password" "$registry_host"
@@ -190,4 +191,25 @@ main() {
   fi
 }
 
+run_crond() {
+  mkdir -p /etc/cron.d
+  echo "${CRON_SETTING:-} BASH_ENV=/save-env /usr/local/bin/shepherd >> /var/log/shepherd.log 2>&1" > /etc/cron.d/shepherd
+  chmod 0644 /etc/cron.d/shepherd
+  export RUN_ONCE_AND_EXIT='true'
+  export CRON_SETTING=''
+  env > /save-env
+  crontab /etc/cron.d/shepherd
+  touch /var/log/cron.log
+  touch /var/log/shepherd.log
+  crond -L /var/log/cron.log && tail -f /var/log/cron.log -f /var/log/shepherd.log
+}
+
+main() {
+  if [[ -z "${CRON_SETTING:-}" ]]; then
+    run_main "$@"
+  else
+    run_crond "$@"
+  fi
+}
+
 main "$@"