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"Cannot get RRD data" error and how to troubleshoot.

Problem

You may be impacted by a Cannot Create Graph error:


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

-rw-rw---- 1 mysite mysite      93 Jun  2 07:21 CPU_Utilization_Packet_CPU_2.info
-rw-r--r-- 1 mysite mysite  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 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/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_1.rrd
2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Mgmt_CPU.rrd
2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_0.rrd

Solution

Unfortunately, for some reason, one of the files is missing. In that case, it is the .rrd file. So to make the graphs 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 of files to delete. Please replace echo $i with rm $i in order to delete those files.

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

Checkmk does not delete any .rrd file. So it could be deleted by a custom cleaning job!




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