Resolved 502, 504 Bad Gateway

[Kingsley]

Try this setting on Apache setting page under tools & setting let's

see the image Imgur

Same problem here! I'm totally in panic. All wordpress websites are down, first to go down a big website some days ago with random 504 gateway error. Now all. Without a reason. Who can explain me what's going on and help me? PLEASE!

 

[D4NY]

The problem seems to be limited to WordPress websites. Did you solve the problem with that settings?
I've tried to disable and re-enable firewall. I had mod-security on and now i've disabled it. At the moment all WordPress websites are running very fast but not the biggest one (2000 sessions/day with about 40-50 people connected at the same time). It is still very slow exactly the last two weeks.
But the question is why? Why this one? And why for some time also all other WordPress websites? No overload on the server, all cores 4.9.8. and all plugin to the latest version. Phisical server with 32gb ram, 8 core, Plesk 17.8.1 on Debian 9.

 

[D4NY]

Looking at the log files of the domains involved:
SITE A ---> 9294#0: *4689427 upstream timed out (110: Connection timed out) while SSL handshaking to upstream
SITE B ---> 20920#0: *4715652 upstream timed out (110: Connection timed out) while reading response header from upstream
SITE C ---> 9294#0: *4690483 upstream timed out (110: Connection timed out) while SSL handshaking to upstream
SIDE D ---> 9294#0: *4691618 upstream timed out (110: Connection timed out) while SSL handshaking to upstream
20920#0: *4695502 peer closed connection in SSL handshake (104: Connection reset by peer) while SSL handshaking to upstream
SITE E ---> 20502#0: *4695093 peer closed connection in SSL handshake (104: Connection reset by peer) while SSL handshaking to upstream

Site A B C D are all wordpress, Site D is a fresh installed wordpress, no plugin, no traffic, Site E is not wordpress

 

[AtakanK]

I guess you have 5XX nginx problem. Probably open file limit or timeout limits doing that.

Nginx fails: Too many open files
A website is not accessible with "Nginx 504 Gateway Time-out" (i suggest 600s btw)
Website is sometimes inaccessible via HTTPS: SSL handshake failed (if problem not resolved)