add side container which backups tt-rss database once a week

bump alpine image to 3.12

app/Dockerfile

@@ -1,7 +1,7 @@
-FROM alpine:3.9
+FROM alpine:3.12
 EXPOSE 9000/tcp
 
-RUN apk add --no-cache php7 php7-fpm \
+RUN apk add --no-cache dcron php7 php7-fpm \
 	php7-pdo php7-gd php7-pgsql php7-pdo_pgsql php7-mbstring \
 	php7-intl php7-xml php7-curl php7-session \
 	php7-dom php7-fileinfo php7-json \
@@ -11,6 +11,8 @@ RUN apk add --no-cache php7 php7-fpm \
 ADD startup.sh /
 ADD updater.sh /
 ADD index.php /
+ADD dcron.sh /
+ADD backup-database.sh /etc/periodic/weekly/backup-database
 
 RUN sed -i.bak 's/^listen = 127.0.0.1:9000/listen = 9000/' /etc/php7/php-fpm.d/www.conf
 RUN sed -i.bak 's/\(memory_limit =\) 128M/\1 256M/' /etc/php7/php.ini

app/backup-database.sh

@@ -0,0 +1,22 @@
+#!/bin/sh -e
+
+DST_DIR=/backups
+KEEP_DAYS=28
+
+if pg_isready -h $DB_HOST -U $DB_USER; then
+	DST_FILE=ttrss-backup-$(date +%Y%m%d).sql.gz
+
+	echo backing up tt-rss database to $DST_DIR/$DST_FILE...
+
+	export PGPASSWORD=$DB_PASS 
+
+	pg_dump --clean -h $DB_HOST -U $DB_USER $DB_NAME | gzip > $DST_DIR/$DST_FILE
+
+	echo cleaning up...
+
+	find $DST_DIR -type f -name '*.sql.gz' -mtime +$KEEP_DAYS -delete
+
+	echo done.
+else
+	echo backup failed: database is not ready.
+fi

app/dcron.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+# https://github.com/dubiousjim/dcron/issues/13
+set -e
+
+/usr/sbin/crond "$@"