little fix to avoid multiple instances of mapcrafter

minor fixes to avoid initial logging problem

Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.04
+FROM ubuntu:18.04
 MAINTAINER muebau <hb1c@gmx.net>
 
 ENV DEBIAN_FRONTEND noninteractive
@@ -24,6 +24,7 @@ RUN apt-get update && \
 ADD crontab /etc/cron.d/mapcrafter-cron
 RUN chmod 0644 /etc/cron.d/mapcrafter-cron
 RUN touch /var/log/cron.log
+RUN echo "container created" >> /var/log/cron.log
 
 ADD render.sh /render
 RUN chmod 0777 /render

render.sh

@@ -3,4 +3,9 @@ if [ ! -f /config/render.conf ]; then
     cp /render.conf /config/render.conf
 fi
 
-mapcrafter -c /config/render.conf -j 2 >> /var/log/cron.log 2>&1
+RUNNINGMAPCRAFTERS=$(pgrep -c mapcrafter)
+if [ $RUNNINGMAPCRAFTERS == "0" ]; then
+    mapcrafter -c /config/render.conf -j 2 >> /var/log/cron.log 2>&1
+else
+    echo "Found $RUNNINGMAPCRAFTERS instances of mapcrafter. So no new instance was started." >> /var/log/cron.log
+fi