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If you are Experiencing issues with a Pi-hole install that has non-standard elements (e.g you are using nginx instead of lighttpd, or there is some other aspect of your install that is customised) - please use the Community Help category.
Pi hole working any Time.
I set up pi-hole on a clean Raspberry setup. Everything works fine so far, but after a few days I don't have access to any URLs. Pi hole doesn't show any faults. Setting DNS away from pi hole in router settings will give internet access again.
Your debug log shows that Pi-hole is working normally:
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] web-reco.searchmachinevisionnsweb-reco.marketing-ns.prod-cvs.net.zooplus.it is 0.0.0.0 on lo (127.0.0.1)
[✓] web-reco.searchmachinevisionnsweb-reco.marketing-ns.prod-cvs.net.zooplus.it is 0.0.0.0 on eth0 (192.168.88.145)
[✓] doubleclick.com is 22.214.171.124 via a remote, public DNS server (126.96.36.199)
Let's take a look at the traffic volume Pi-hole is processing. Please post the output of this command from the Pi terminal:
This is not particularly high traffic volume, but your debug log shows a few periods when the upstream DNS server has not responded due to a burst of DNS traffic:
-----tail of FTL.log------
[2022-09-02 04:06:08.758 570M] Resizing "FTL-dns-cache" from 200704 to (12800 * 16) == 204800 (/dev/shm: 4.6MB used, 225.2MB total, FTL uses 4.6MB)
[2022-09-02 07:27:04.752 570M] WARNING in dnsmasq core: Maximum number of concurrent DNS queries reached (max: 150)
[2022-09-02 07:27:05.754 570M] SQLite3 message: database is locked in "INSERT INTO message (timestamp,type,message,blob1,blob2,blob3,blob4,blob5) VALUES ((cast(strftime('%s', 'now') as int)),?,?,?,?,?,?,?);" (5)
[2022-09-02 07:27:05.755 570M] add_message(type=5, message=Maximum number of concurrent DNS queries reached (max: 150)) - SQL error prepare: database is locked