DNS service not running, Lost connection to API

[qkt]

Expected Behaviour:

Pi-blocks ads as expected and access to websites is not impacted.

Current system information:
Raspbian GNU/Linux v10
Current Pi-hole version is v5.17.2
Current web version is v5.20.2
Current FTL version is v5.23

Actual Behaviour:

Ads are not blocked, and devices are unable to access websites.
Message in sidebar: "DNS service not running"
On dashboard: "Lost connection to API"

Nothing seemed to trigger this, it started happening seemingly out of the blue. I attempted to update Pi-hole, as well as reboot the system and even repair but none the less, the problem was not resolved.

I tried to restart FTL, which also did nothing. Sifting through the other related posts here, I wasn't able to find a solution based on the same problems of others.

Debug Token:

https://tricorder.pi-hole.net/p71aJ3Ya/

[krackajak]

I had the same issue this morning. I don't know why this helped but it worked for me:

sudo service pihole-FTL stop
sudo mv /etc/pihole/pihole-FTL.db /etc/pihole/pihole-FTL.db.old
sudo service pihole-FTL start

It's basically wiping out the pihole db. Not sure why/how it got full/corrupted. I didn't have any obvious error message or issues in the debug output.

[jfb]

From the Pi terminal, please provide the outputs to the following commands:

echo ">stats >quit" | nc localhost 4711

echo ">top-clients >quit" | nc localhost 4711

echo ">top-domains >quit" | nc localhost 4711

echo ">top-ads >quit" | nc localhost 4711

echo ">querytypes >quit" | nc localhost 4711

Note - if you format your text output with the </> icon (preformatted text) in the reply window, it will be much more readable.

[qkt]

stats:

domains_being_blocked 910169
dns_queries_today 0
ads_blocked_today 0
ads_percentage_today 0.000000
unique_domains 0
queries_forwarded 0
queries_cached 0
clients_ever_seen 0
unique_clients 0
dns_queries_all_types 0
reply_UNKNOWN 0
reply_NODATA 0
reply_NXDOMAIN 0
reply_CNAME 0
reply_IP 0
reply_DOMAIN 0
reply_RRNAME 0
reply_SERVFAIL 0
reply_REFUSED 0
reply_NOTIMP 0
reply_OTHER 0
reply_DNSSEC 0
reply_NONE 0
reply_BLOB 0
dns_queries_all_replies 0
privacy_level 0
status enabled

querytypes:

A (IPv4): 0.00
AAAA (IPv6): 0.00
ANY: 0.00
SRV: 0.00
SOA: 0.00
PTR: 0.00
TXT: 0.00
NAPTR: 0.00
MX: 0.00
DS: 0.00
RRSIG: 0.00
DNSKEY: 0.00
NS: 0.00
OTHER: 0.00

SVCB: 0.00
HTTPS: 0.00

All other commands return a newline. As a heads up, I have pointed my router DNS away from the pi IP to ensure I have working internet. I figure that likely will have an impact on what these commands are returning.

[qkt]

krackajak's solution did indeed solve the problem. I'm not entirely sure why but it is definitely an issue with FTL. It would be great to know the underlying issue in case it returns, but I am not complaining for the availability of a solution. If I encounter the problem again, I can create a new post to dig a bit deeper.