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Problem

You may be affected by that:

impacted by a Cannot Create Graph error.

Image Added

To visualize a graph, Checkmk is using uses RRD. The RRD needs, by nature, two files:

-rw-rw---- 1 mastermysite mastermysite      93 Jun  2 07:21 CPU_Utilization_Packet_CPU_2.info
-rw-r--r-- 1 mastermysite mastermysite  384952 Jun  2 11:22 CPU_Utilization_Packet_CPU_2.rrd

The .rrd file stores all the data, and the .info file defines the service metrics. If one of the file files is missing, you will face the message above. This message will also be displayed in the cmc.log:

OMD[mysite]:~$ tail -f var/log/cmc.log
2022-06-02 12:09:41 [4] [main] [rrd] [rrdcached at /omd/sites/mastermysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mastermysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_1.rrd
2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mastermysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mastermysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Mgmt_CPU.rrd
2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mastermysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mastermysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_0.rrd

Solution

Unfortunately, for some reasons reason, one of the file files is missing. In that case, it is the .rrd file. So to make the graphs working work again, you need to  stop the site, find all the .info files with a missing .rrd file, and to delete them manually: 

OMD[mysite]:~$ for i in $(find ~/var/check_mk/rrd -name *.info); do test -e ${i%info}rrd || echo $i; done
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/PING.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Mgmt_CPU.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_1.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_0.info

Now you have a list with of files to delete. Please replace echo $i with rm $i in order to delete those files.

After you deleted delete the affected files, you need to start the site , so the new files are created.

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