No Changes, Two Separate Sites Now Error 500

[The Britain]

I have two seperate sites, https://accursedfarms.com and https://gorillagong.com

Both sites have gone down and show an IPB error stating

Quote

"We're sorry, but a temporary technical error has occurred which means we cannot display this site right now.
You can try again by clicking the button below, or try again later."

Two separate sites running two separate installations of IPB on two separate databases, no updates, no new plugins, no new themes, no edits, no server updates, no messing with folder perms, absolutely nothing at all changed and they're both down at the same time. All of my other sites work. I've literally not touched them at all, and they've both went down at the same time with the same error. Anyone have any ideas?

[Daniel F]

DB server down? Did the web host change anything? Do you see any logged errors?

[The Britain]

Just now, Daniel F said:

DB server down? Did the web host change anything? Do you see any logged errors?

Hey thanks for getting back to me, nothing changed. No logs but there is some definitive weirdness going on. I need someone from the security side to get ahold of me.

[The Britain]

Ok it gets weirder, I did a full site restore from a week ago and both sites still don't work. All the other non-ipb sites on the server work, but the two IPB sites do not work. I want to clarify I have a VPS and I control the environment, my host doesn't change anything.

[Sonya*]

5 hours ago, The Britain said:

No logs

There are should be apache or php logs on your server. If you get 500 error, then it is logged there. You have to check it. Generally with 500 error your server says to you: "Something went wrong, but I do not know exactly what." That is. There are can be 1000 reasons for it. The only way to figure it out, it to check the server logs. 

I would also check your https certificate. It is probably expired. I can see that both sites are reachable with http and https. There is should be at least redirect from http to https. 

[The Britain]

Alright after a ton of looking around we narrowed it down to Redis. We didn't change anything but Redis.php went haywire in the IPB package and made error logs so large it had a buffer underflow. Where is the option in the database under IPB_sys_conf_settings to disable all caching? Thanks for your help. 

[The Britain]

How can I disable redis from the backend? Will this help with the problem so at-least I can get the sites operational?

[The Britain]

That 100% was the issue and I solved it for anyone in the future. You need to look at constants.php in the root and remove everything but the site key to disable Redis. I disabled Redis on the server and remove those constants, the problem went away and the site loaded.