Graphs does not display until host restart

Expected Behaviour:

The graphs are displayed in the web UI after start the Pi where Pi-hole is installed.

Actual Behaviour:

I switch off the Pi running Pi-hole with normal shutdown if I’m not at home for some time. The graphs are not displayed in any web UI (Chrome, FF on Windows or Safari on an iPad) after start the Pi. This does not recover if I let the Pi run for some days. Restarting a browser or client does not help to display the graphs. That I expect it’s more a Pi-hole related issue.

The only way to get the Graphs be shown is to restart the Pi with “shutdown -r”. The graphs are displayed on all devices afterwards.

The following debug token is provided after a restart with graphs working.

Debug Token:

A Debug Token after a new start after some days while the graphs are not working:

DNSSEC enabled ?

grep DNSSEC /etc/pihole/setupVars.conf

Check date/time that may be incorrect because of the chicken egg dilemma on SBC’s without a real time clock:

When you start Pi-Hole, the information to populate the dashboard is read from the long term database at /etc/pihole/pihole-FTL.db. The default is to read 24 hours of data.

If there is a problem with your database, then this can affect this process. In your debug log, Pi-Hole is doing a number of activities to prune the database.

   [2019-12-01 18:00:00.112 674] Notice: Database size is 134.03 MB, deleted 891 rows
   [2019-12-01 19:00:00.157 674] Notice: Database size is 134.03 MB, deleted 346 rows
   [2019-12-01 20:00:00.115 674] Notice: Database size is 134.03 MB, deleted 630 rows

As a test, I would temporarily move the long term database and restart FTL. If the problem resolves after 24 hours of data collection, then it would indicate a problem with the existing database.

sudo service pihole-FTL stop
sudo mv /etc/pihole/pihole-FTL.db /etc/pihole/pihole-FTL-old.db
sudo service pihole-FTL start
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back at home today. DNSSEC is disabled:

pi@pihole:~ $ grep DNSSEC /etc/pihole/setupVars.conf

I’ll try the FTL DB stuff now. Report back tomorrow.

Edit: The graphs is displayed at the moment. But it’s unclear if this is because the DB is changed. Or if this is the same behavior as the usual restart. Lets see later.