timed backup script with backup time (#339)

* Update backup.sh

- new zammad-timed-backup which uses fixed backup time $BACKUP_TIME

* Update docker-compose.yml

- $BACKUP_TIME added
- timed backup as command

* merge request and linting fixes

* arithmetic linting fix

* not related to merge request but fixes linting in check_railsserver_available

docker-compose.yml

@@ -10,10 +10,11 @@ services:
       - zammad-postgresql
     entrypoint: /usr/local/bin/backup.sh
     environment:
-      - BACKUP_SLEEP=86400
+      - BACKUP_TIME=03:00
       - HOLD_DAYS=10
       - POSTGRESQL_USER=${POSTGRES_USER}
       - POSTGRESQL_PASSWORD=${POSTGRES_PASS}
+      - TZ=Europe/Berlin
     image: postgres:${POSTGRES_VERSION}
     restart: ${RESTART}
     volumes:

scripts/backup.sh

@@ -11,7 +11,7 @@ set -e
 : "${POSTGRESQL_DB:=zammad_production}"
 
 function check_railsserver_available {
-  until (echo > /dev/tcp/${ZAMMAD_RAILSSERVER_HOST}/${ZAMMAD_RAILSSERVER_PORT}) &> /dev/null; do
+  until (echo > "/dev/tcp/$ZAMMAD_RAILSSERVER_HOST/$ZAMMAD_RAILSSERVER_PORT") &> /dev/null; do
     echo "waiting for railsserver to be ready..."
     sleep 60
   done
@@ -43,10 +43,15 @@ if [ "$1" = 'zammad-backup' ]; then
   check_railsserver_available
 
   while true; do
+    NOW_TIMESTAMP=$(date +%s)
+    TOMORROW_DATE=$(date -d@"$((NOW_TIMESTAMP + 24*60*60))" +%Y-%m-%d)
+    
     zammad_backup
 
-    # wait until next backup
-    sleep "${BACKUP_SLEEP}"
+    NEXT_TIMESTAMP=$(date -d "$TOMORROW_DATE $BACKUP_TIME" +%s)
+    NOW_TIMESTAMP=$(date +%s)
+
+    sleep $((NEXT_TIMESTAMP - NOW_TIMESTAMP))
   done
 fi