Hey Drookie,

Can you let me know how you solved this issue?

We are facing a similar issue which results in 502 gateway error and I'm not able to find a solution for it.

Below is the error log from /var/log/nginx/error.log

2018/03/22 01:34:49 [error] 8779#0: *13133 no live upstreams while connecting to upstream, client: 207.189.113.68, server: 192.168.10.4, request: "POST /upload_app HTTP/1.1", upstream: "uwsgi://upload_clusters", host: "173.255.9.88"
2018/03/22 01:34:50 [error] 8779#0: *13136 no live upstreams while connecting to upstream, client: 207.189.113.68, server: 192.168.10.4, request: "POST /upload_app HTTP/1.1", upstream: "uwsgi://upload_clusters", host: "173.255.9.88"
2018/03/22 01:34:50 [error] 8779#0: *13143 no live upstreams while connecting to upstream, client: 207.189.113.68, server: 192.168.10.4, request: "POST /upload_app HTTP/1.1", upstream: "uwsgi://upload_clusters", host: "173.255.9.88"
2018/03/22 01:34:50 [error] 8779#0: *13144 no live upstreams while connecting to upstream, client: 207.189.113.68, server: 192.168.10.4, request: "POST /upload_app HTTP/1.1", upstream: "uwsgi://upload_clusters", host: "173.255.9.88"

We dont get this issue for all requests but for some random requests in between. Below is the access log from /var/log/nginx/access.log
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 502 198 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 502 198 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 502 198 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:29 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:34 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:34 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:36 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:37 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:39 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:42 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:42 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:45 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:46 -0700] "POST /upload_app HTTP/1.1" 502 198 "-" "Apache-HttpClient/4.0.3 (java 1.5)"
207.189.113.68 - - [22/Mar/2018:02:15:46 -0700] "POST /upload_app HTTP/1.1" 200 162 "-" "Apache-HttpClient/4.0.3 (java 1.5)"

As you can see some requests got 200(success) response and some got 502(gateway error). I have tried parameter tuning by increasing timeouts but no help.

It would be really helpful if you can let me know what worked for you. Thanks.