React JS app in Docker with Nginx

Dockerfile

FROM node:12-alpine as build
WORKDIR /www

ENV REACT_APP_KEYCLOAK_URL %REACT_APP_KEYCLOAK_URL%
ENV REACT_APP_KEYCLOAK_REALM %REACT_APP_KEYCLOAK_REALM%

COPY package*json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:1.19.9-alpine
WORKDIR /www

COPY --from=build /www/build .
COPY entrypoint.sh .
COPY nginx.conf /etc/nginx/conf.d/default.conf

CMD ./entrypoint.sh

entrypoint.sh

#!/bin/sh

set -ex

replace_var() {
    # $1 var name
    # $2 file name
    eval "value=\$$1"
    if [ -z "$value" ]; then
        echo "Undefined variable $1"
        exit 1
    fi
    sed -i "s,%$1%,$value,g" $2
}

# go through all JS files and replace %VAR_NAME% with VAR_NAME value from env variables
find . -type f -name "*.js" | while read filename; do
    replace_var REACT_APP_KEYCLOAK_URL $filename
    replace_var REACT_APP_KEYCLOAK_REALM $filename
done

nginx -g "daemon off;"

gistfile1.txt

map $sent_http_content_type $expires {
  default                    off;
  text/html                  epoch;
  text/css                   max;
  application/javascript     max;
  ~image/                    max;
}


server {
  listen 80 default_server;
  server_name webapp;
  root /www;

  expires $expires;

  ##
  # Gzip Settings
  ##
  gzip on;
  gzip_http_version 1.1;
  gzip_disable      "MSIE [1-6]\.";
  gzip_min_length   1100;
  gzip_vary         on;
  gzip_proxied      expired no-cache no-store private auth;
  gzip_types        text/plain text/css application/json application/javascript application/x-javascript text/xml application/xml application/xml+rss text/javascript;
  gzip_comp_level   9;

  # Routes without file extension e.g. /user/1
  location / {
    try_files $uri /index.html;
  }

  # 404 if a file is requested (so the main app isn't served)
  # make sure this regex doesn't catch paths that end with .\d+, because we're using versions (xxx.yyy.zzz) in URL path params
  location ~ ^.+\.[a-zA-Z].+$ {
    try_files $uri =404;
  }

}

nginx.conf

map $sent_http_content_type $expires {
  default                    off;
  text/html                  epoch;
  text/css                   max;
  application/javascript     max;
  ~image/                    max;
}


server {
  listen 80 default_server;
  server_name webapp;
  root /www;

  expires $expires;

  ##
  # Gzip Settings
  ##
  gzip on;
  gzip_http_version 1.1;
  gzip_disable      "MSIE [1-6]\.";
  gzip_min_length   1100;
  gzip_vary         on;
  gzip_proxied      expired no-cache no-store private auth;
  gzip_types        text/plain text/css application/json application/javascript application/x-javascript text/xml application/xml application/xml+rss text/javascript;
  gzip_comp_level   9;

  # Routes without file extension e.g. /user/1
  location / {
    try_files $uri /index.html;
  }

  # 404 if a file is requested (so the main app isn't served)
  # make sure this regex doesn't catch paths that end with .\d+, because we're using versions (xxx.yyy.zzz) in URL path params
  location ~ ^.+\.[a-zA-Z].+$ {
    try_files $uri =404;
  }

}