nginx docker compose redirect delay - docker

Question

I'm having a particularly odd behaviour with my docker-compose and nginx setup. I am trying to have nginx proxy_pass requests to a backend web service. The web service is Spring Boot, but I don't believe that's relevant. My web service will issue a 302 redirect to users who are not authenticated, sending them to a /login page. This all seems to work as expected except for an indeterminate period of time when I bring the docker-compose up. Early requests to the service which result in 302 responses result in timeouts, whilst requests direct to the /login page return as expected immediately. After an indeterminate period of time, usually minutes, something seems to stabilise and everything works as expected. I've verified the behaviour using chrome from a client machine and curl directly on the host running the compose. I believe the 302 responses are somehow getting dropped but I'm not sure.
Can anyone spot a problem?
version: '3.5'
services:
proxy:
image: nginx:latest
container_name: "proxy"
restart: always
volumes:
- blah:/etc/nginx
ports:
- 80:80
- 443:443
webservice:
image: "webservice:latest"
container_name: "webservice"
restart: always
ports:
- 8080:8080
Nginx Config:
worker_processes auto;
events { }
http {
server {
listen 80 default_server;
listen 443 default_server ssl;
ssl_certificate /etc/nginx/cert;
ssl_certificate_key /etc/nginx/key;
if ($scheme = http) {
return 301 https://$host:443$request_uri;
}
gzip on;
gzip_types text/plain application/xml application/json application/javascript;
location / {
proxy_http_version 1.1;
proxy_pass http://webservice:8080/;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_set_header Host $host:$server_port;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Port $server_port;
access_log /etc/nginx/log/access.log combined;
error_log /etc/nginx/log/error.log warn;
}
}
}