add MAX_BACKUPS to limit the number of backups

Author: tifayuki

README.md

@@ -25,4 +25,5 @@ Moreover, if you link `tutum/mongodb-backup` to a mongodb container(e.g. `tutum/
     MONGODB_PASS    the password of your mongodb database
     MONGODB_DB      the database name to dump. If not specified, it will dump all the databases
     EXTRA_OPTS      the extra options to pass to mongodump command
-    CRON_TIME       the interval of cron job to run mongodump. "0 0 * * *" by default, which is every day at 00:00
+    CRON_TIME       the interval of cron job to run mongodump. `0 0 * * *` by default, which is every day at 00:00
+    MAX_BACKUPS     the number of backups to keep. When reaching the limit, the old backup will be discarded. No limit, by default

run.sh

@@ -17,10 +17,33 @@ MONGODB_PASS=${MONGODB_PASS:-${MONGODB_ENV_MONGODB_PASS}}
 [[ ( -n "${MONGODB_PASS}" ) ]] && PASS_STR=" --password ${MONGODB_PASS}"
 [[ ( -n "${MONGODB_DB}" ) ]] && USER_STR=" --db ${MONGODB_DB}"
 
-CMD="mongodump --out /backup/"'$(date +\%Y.\%m.\%d.\%H\%M\%S)'" --host ${MONGODB_HOST} --port ${MONGODB_PORT} ${USER_STR}${PASS_STR}${DB_STR} ${EXTRA_OPTS}"
-echo "${CRON_TIME} ${CMD} >> /mongo_backup.log 2>&1" > /crontab.conf
+BACKUP_CMD="mongodump --out /backup/"'$(date +\%Y.\%m.\%d.\%H\%M\%S)'" --host ${MONGODB_HOST} --port ${MONGODB_PORT} ${USER_STR}${PASS_STR}${DB_STR} ${EXTRA_OPTS}"
+
+
+echo "=> Creating backup script"
+cat <<EOF >> /backup.sh
+#!/bin/bash
+MAX_BACKUPS=${MAX_BACKUPS}
+
+echo "=> Starting backup"
+if [ -n "\${MAX_BACKUPS}" ]; then
+    while [ \$(ls /backup -N1 | wc -l) -ge \${MAX_BACKUPS} ];
+    do
+        BACKUP_TO_BE_DELETED=\$(ls /backup -N1 | sort | head -n 1)
+        echo "Deleting backup \${BACKUP_TO_BE_DELETED}"
+        rm -rf /backup/\${BACKUP_TO_BE_DELETED}
+    done
+fi
+${BACKUP_CMD}
+echo "=> Backup done"
+EOF
+chmod +x /backup.sh
+
+echo "${CRON_TIME} /backup.sh >> /mongo_backup.log 2>&1" > /crontab.conf
+echo "=> Adding cron job"
 crontab  /crontab.conf
 crontab -l
 touch /mongo_backup.log
 tail -F /mongo_backup.log &
+echo "=> Running cron job"
 exec cron -f