502 Bad Gateway with pgadmin4 behind nginx? - docker

Question

I have an api running in docker with:
nginx
nodejs api
postgresql
pgadmin4
certbot
When I try to add an endpoint for pgadmin so I can work with the database, I get a 502 bad gateway regardless how I'm setting up the ports for proxy_pass or in docker-compose for the actual container for pgadmin.
docker-compose.yml
version: "3"
services:
webserver:
image: nginx:mainline-alpine
container_name: webserver
restart: unless-stopped
ports:
- "80:80"
- "443:443"
volumes:
- web-root:/var/www/html
- ./nginx-conf:/etc/nginx/conf.d
- certbot-etc:/etc/letsencrypt
- certbot-var:/var/lib/letsencrypt
- dhparam:/etc/ssl/certs
depends_on:
- api-graphql
- api-postgres-pgadmin
networks:
- app-network
certbot:
image: certbot/certbot
container_name: certbot
volumes:
- certbot-etc:/etc/letsencrypt
- certbot-var:/var/lib/letsencrypt
- web-root:/var/www/html
depends_on:
- webserver
command: certonly --force-renewal --webroot --expand --webroot-path=/var/www/html --email contact#name.dev --agree-tos --no-eff-email -d api.name.dev
api-graphql:
container_name: api-graphql
restart: always
build: .
depends_on:
- api-postgres
networks:
- app-network
api-postgres-pgadmin:
container_name: api-postgres-pgadmin
image: dpage/pgadmin4:latest
networks:
- app-network
ports:
- "8080:8080"
environment:
- PGADMIN_DEFAULT_EMAIL=name#gmail.com
- PGADMIN_DEFAULT_PASSWORD=pass
depends_on:
- api-postgres
api-postgres:
container_name: api-postgres
image: postgres:10
volumes:
- ./data:/data/db
networks:
- app-network
environment:
- POSTGRES_PASSWORD=pass
networks:
app-network:
driver: bridge
volumes:
certbot-etc:
certbot-var:
web-root:
driver: local
driver_opts:
type: none
device: /home/name/api/data
o: bind
dhparam:
driver: local
driver_opts:
type: none
device: /home/name/api/dhparam
o: bind
nginx.conf
server {
listen 80;
listen [::]:80;
server_name api.name.dev;
location ~ /.well-known/acme-challenge {
allow all;
root /var/www/html;
}
location / {
rewrite ^ https://$host$request_uri? permanent;
}
}
server {
listen 443 ssl http2;
listen [::]:443 ssl http2;
server_name api.name.dev;
server_tokens off;
ssl_certificate /etc/letsencrypt/live/api.name.dev/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/api.name.dev/privkey.pem;
ssl_buffer_size 8k;
ssl_dhparam /etc/ssl/certs/dhparam-2048.pem;
ssl_protocols TLSv1.2 TLSv1.1 TLSv1;
ssl_prefer_server_ciphers on;
ssl_ciphers ECDH+AESGCM:ECDH+AES256:ECDH+AES128:DH+3DES:!ADH:!AECDH:!MD5;
ssl_ecdh_curve secp384r1;
ssl_session_tickets off;
ssl_stapling on;
ssl_stapling_verify on;
resolver 8.8.8.8;
location / {
try_files $uri #api-graphql;
}
location #api-graphql {
proxy_pass http://api-graphql:8080;
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;
add_header Referrer-Policy "no-referrer-when-downgrade" always;
add_header Content-Security-Policy "default-src * data: 'unsafe-eval' 'unsafe-inline'" always;
# add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
# enable strict transport security only if you understand the implications
}
location /pg {
try_files $uri #api-postgres-pgadmin;
}
location #api-postgres-pgadmin {
proxy_pass http://api-postgres-pgadmin:8080;
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;
add_header Referrer-Policy "no-referrer-when-downgrade" always;
add_header Content-Security-Policy "default-src * data: 'unsafe-eval' 'unsafe-inline'" always;
# add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
# enable strict transport security only if you understand the implications
}
root /var/www/html;
index index.html index.htm index.nginx-debian.html;
}
Is this just not going to work with having a http://something.com/stuff work with pgadmin? Do we have to us a parent sub domain like stuff.something.com ?

Answer 1

Bad gateway means nginx cannot reach the backend service you've identified. That could be DNS issues (which don't appear to be an issue here), containers on different networks (again, not an issue), or communicating to a port the container isn't listening on.
Checking the pgadmin image docs, this image appears to listen on port 80, not port 8080. So you'll need to adjust nginx to connect to that port instead:
location #api-postgres-pgadmin {
# adjust the next line, removing port 8080, port 80 is the default for http
proxy_pass http://api-postgres-pgadmin;
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;
add_header Referrer-Policy "no-referrer-when-downgrade" always;
add_header Content-Security-Policy "default-src * data: 'unsafe-eval' 'unsafe-inline'" always;
# add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;
# enable strict transport security only if you understand the implications
}