When selecting a large date range on the long term data Query Log, say last 30 or even last 7 days, I’d be greeted with the following error message and some more information in Lighttpd’s logs.

And the relevant line in /var/log/lighttpd/error.log:

2020-06-07 19:40:24: (mod_fastcgi.c.421) FastCGI-stderr: PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 10489856 bytes) in /var/www/html/admin/api_db.php on line 422

I’m running Pi-hole on an old desktop system with greater resources than the Raspberry Pis I own. That box has 4GB RAM.

Once I increased the memory limit in the relevant php.ini, the Internal Server Error 500 went away.

• I noticed when I increased the memory_limit to 512M, I had better luck loading the last 7 days worth of data.
• I was successfully able to see the last 30 days worth of data by giving PHP a whopping limit of 2G!
• Data from “all time” is still unavailable to me, I don’t have the RAM available to let PHP use all of it.

According to this post on the Pi-hole discourse, the next major version of Pi-hole will have a new, more clever, API.