Google Cloud Compute Engine上的Flask + NGINX + UWSGI提供了502错误的网关

Question

I'm trying to set up Pybossa (webapp built with Flask) on an NGINX server running on Google Cloud (following this tutorial, for reference). I think there is something wrong with the virtual host file I'm using since as soon as I enable it the server returns 502 bad gateway. The Google Compute Engine VM instance is running Debian 8.

The full hosts file is here:

 server { listen 80; server_name _; large_client_header_buffers 4 32k; real_ip_header X-Forwarded-For; # change that to your pybossa directory root /home/pybossa/pybossa; client_max_body_size 5M; if (-f /home/pybossa/pybossa/503.html) { return 503; } error_page 503 @maintenance; location / { try_files $uri @pybossa; } location @pybossa { include uwsgi_params; uwsgi_pass unix:/tmp/pybossa.sock; } location /static { # change that to your pybossa static directory alias /home/pybossa/pybossa/pybossa/themes/default/static; autoindex on; expires max; } location ~ /api/app { rewrite ^/api/app /api/project$1 permanent; } location ~ /app { rewrite ^/app(.*) /project$1 permanent; } error_page 503 @maintenance; location @maintenance { if ($uri !~ ^/static/) { rewrite ^(.*)$ /503.html break; } } } 

And the uwsgi config file:

 [uwsgi] socket = /tmp/pybossa.sock chmod-socket = 666 chdir = /home/pybossa/pybossa pythonpath = .. virtualenv = /home/pybossa/pybossa/env module = run:app cpu-affinity = 1 processes = 2 threads = 2 stats = /tmp/pybossa-stats.sock buffer-size = 65535 

I had initially set up my own NGINX server, which didn't work. Now I'm running it in an NGINX server deployed by Google cloud, which works fine until I enable the virtual hosts file in `/etc/nginx/sites-enabled/.

The /var/log/nginx/error.log contains the following:

 2017/08/16 21:53:30 [alert] 439#0: *21 open socket #13 left in connection 4 2017/08/16 21:53:30 [alert] 439#0: *21 open socket #13 left in connection 4 2017/08/16 21:53:30 [alert] 439#0: aborting 2017/08/16 21:53:32 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:13 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:14 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:14 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:35 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:36 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:37 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 21:54:51 [crit] 16744#0: *1 connect() to unix:/tmp/pybossa.sock failed (2: No such file or directory) while connecting to upstream, client: 68.107.113.211, server: _, reques t: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 

I'm new to web app development and haven't used Flask or NGINX before. Appreciate any help I can get.

UPDATE: After fixing the issue where uwsgi wasn't running, now error log says

 2017/08/16 23:53:27 [alert] 23944#0: *26 open socket #7 left in connection 3 2017/08/16 23:53:27 [alert] 23944#0: aborting 2017/08/16 23:53:30 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:53:30 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:53:31 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:53:31 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:53:31 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:54:29 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 2017/08/16 23:54:30 [error] 24536#0: *1 connect() to unix:/tmp/pybossa.sock failed (111: Connection refused) while connecting to upstream, client: 68.107.113.211, server: _, request: "GET / HTTP/1.1", upstream: "uwsgi://unix:/tmp/pybossa.sock:", host: "35.184.197.200" 

Answer 1

The log say No such file or directory is because you don't have set up the socket in your Nginx config , try to add it, something like this:

 location / {
            proxy_pass http://unix:/tmp/pybossa.sock

Answer 2

Check the uwsgi error logs. It should say, why it's failing or returning 500. Also, double check that the socket is created with the proper privileges, so nginx can connect to it.