nginx - Multiple upstream proxies failing -

i've been playing around using docker setup group of web applications sit behind nginx container. i'm using docker-compose manage different services , of individual web service containers work fine when try access them nginx container 1 of them works , it's first 1 try access. if start container group , access app1 page expected if go app2 50x error. if restart group , go app2 first page expected if go app1 50x error now. i'm not sure i'm doing wrong in nginx config. assistance appreciated.

here nginx config:

upstream app1_backend {     server app1:8000; }  upstream app2_backend {     server app2:8000; }  server {     listen 80 default_server;      server_name localhost;      charset utf-8;      #location / {     #    root   /usr/share/nginx/html;     #    index  index.html index.htm;     #}      #error_page  404              /404.html;      # redirect server error pages static page /50x.html     error_page   500 502 503 504  /50x.html;     location = /50x.html {         root   /usr/share/nginx/html;     }      location /static {         alias /static;     }      location /app1/ {         proxy_pass http://app1_backend/;         proxy_http_version 1.1;         proxy_set_header upgrade $http_upgrade;         proxy_set_header connection 'upgrade';         proxy_set_header host $host;         proxy_cache_bypass $http_upgrade;         proxy_set_header x-real-ip $remote_addr;         proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;     }      location /app2/ {         proxy_pass http://app2_backend/;         proxy_http_version 1.1;         proxy_set_header upgrade $http_upgrade;         proxy_set_header connection 'upgrade';         proxy_set_header host $host;         proxy_cache_bypass $http_upgrade;         proxy_set_header x-real-ip $remote_addr;         proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;     } } 

and again can access individual applications @ http://app1:8000/ , http://app2:8000/.

i figured out doing wrong. had server_name localhost;. changing server_name _; fixed issue.