Nginx: Invalid upstream reference

[ragnarkurmwunder]

https://wunder.slack.com/archives/C8UN6AG9W/p1597845597476600

Visiting /core/modules/statistics/statistics.php yields 502 Bad Gateway.

Because:

    upstream php {
        server localhost:9000;
    }

There is nothing listening in Nginx container at port 9000.
localhost is wrong and should be replaced by app.

Solution

1. Instead use this:

    upstream php {
        server app:9000;
    }

2. Replace all occurrences of fastcgi_pass app:9000; by fastcgi_pass php;.