IS IT NGINX OR THE NODE API? A 502 MYSTERY WITH ONE CLUE

Malik Brandt · 2026-05-28T22:52:32.760Z

ugh. our Node API sits behind nginx on the same VM. It listens on 8000. Its been fine for months, but now only under load we get this: [code] if i SSH in and curl localhost:8000 I get a 200 insatntly. Restarting nginx fixes it for a while. Im out of ideas and support tickets are piling up. config hasnt changed in ages, as far as i know. the nginx config test passes, the apps own logs look normal, and CPU and memory on teh box are fine... what should i check first so i stop guessing??

Solved502 nginx reverse-proxy1 replies · 113 views · started 5 mo. ago

Accepted solution by Jonas Dubois — oh ive been there lol start with the nginx error log, it tells u which kind of 502 it is: [code] connect() failed (111: Connection…

Malik Brandt
@nimbushound
3 rep · 1 posts
5 mo. ago
ugh. our Node API sits behind nginx on the same VM. It listens on 8000. Its been fine for months, but now only under load we get this:
```
502 Bad Gateway
nginx
```
if i SSH in and curl localhost:8000 I get a 200 insatntly. Restarting nginx fixes it for a while. Im out of ideas and support tickets are piling up.

config hasnt changed in ages, as far as i know. the nginx config test passes, the apps own logs look normal, and CPU and memory on teh box are fine... what should i check first so i stop guessing??
2
Jonas Dubois
@jonasd919
72 rep · 9 posts
5 mo. ago Accepted solution
oh ive been there lol start with the nginx error log, it tells u which kind of 502 it is:
```
sudo tail -f /var/log/nginx/error.log
```
connect() failed (111: Connection refused) means nothing listens where proxy_pass points. upstream prematurely closed connection means teh app accepted and then dropped the request. no live upstreams means all backends were marked down. hope that helps :)
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