NginX reverse proxy for Kibana over Docker

Question

I have a Docker Compose setup with NginX, ElasticSearch and Kibana like the following:

web:
    build:
      context: .
      dockerfile: ./system/docker/development/web.Dockerfile
    depends_on:
      - app
    volumes:
      - './system/ssl:/etc/ssl/certs'
    networks:
      - mynet
    ports:
      - 80:80
      - 443:443

  elasticsearch_1:
    image: docker.elastic.co/elasticsearch/elasticsearch:7.7.0
    container_name: "${COMPOSE_PROJECT_NAME:-service}_elasticsearch_1"
    environment:
      - node.name=elasticsearch_1
      - cluster.name=es-docker-cluster
      - discovery.seed_hosts=elasticsearch_2,elasticsearch_3
      - cluster.initial_master_nodes=elasticsearch_1,elasticsearch_2,elasticsearch_3
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    ulimits:
      memlock:
        soft: -1
        hard: -1
    volumes:
      - es_volume_1:/usr/share/elasticsearch/data
    ports:
      - 9200:9200
    networks:
      - mynet

  elasticsearch_2:
    image: docker.elastic.co/elasticsearch/elasticsearch:7.7.0
    container_name: "${COMPOSE_PROJECT_NAME:-service}_elasticsearch_2"
    environment:
      - node.name=elasticsearch_2
      - cluster.name=es-docker-cluster
      - discovery.seed_hosts=elasticsearch_1,elasticsearch_3
      - cluster.initial_master_nodes=elasticsearch_1,elasticsearch_2,elasticsearch_3
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    ulimits:
      memlock:
        soft: -1
        hard: -1
    volumes:
      - es_volume_2:/usr/share/elasticsearch/data
    ports:
      - 9201:9201
    networks:
      - mynet

  elasticsearch_3:
    image: docker.elastic.co/elasticsearch/elasticsearch:7.7.0
    container_name: "${COMPOSE_PROJECT_NAME:-service}_elasticsearch_3"
    environment:
      - node.name=elasticsearch_3
      - cluster.name=es-docker-cluster
      - discovery.seed_hosts=elasticsearch_1,elasticsearch_2
      - cluster.initial_master_nodes=elasticsearch_1,elasticsearch_2,elasticsearch_3
      - bootstrap.memory_lock=true
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
    ulimits:
      memlock:
        soft: -1
        hard: -1
    volumes:
      - es_volume_3:/usr/share/elasticsearch/data
    ports:
      - 9202:9202
    networks:
      - mynet

  kibana:
    image: docker.elastic.co/kibana/kibana:7.7.0
    container_name: "${COMPOSE_PROJECT_NAME:-service}_kibana"
    ports:
      - 5601:5601
    environment:
      ELASTICSEARCH_URL: http://elasticsearch_1:9200
      ELASTICSEARCH_HOSTS: http://elasticsearch_1:9200
    networks:
      - mynet
      
volumes:
  es_volume_1: null
  es_volume_2: null
  es_volume_3: null

networks:
  mynet:
    driver: bridge
    ipam:
      config:
      - subnet: 172.18.0.0/24
        gateway: 172.18.0.1

When I (build and) run this using docker-compose up I'm able to access Kibana through URL http://localhost:5601/ but when I try to setup a reverse proxy for the same using NginX, I get a 502 Bad Gateway error. Here's my NginX config file:

server {
   listen 80;
   listen 443 ssl http2;

   ssl_certificate /ssl/localhost.crt;
   ssl_certificate_key /ssl/localhost.key;

  ...

  location /app/kibana {
     proxy_pass http://localhost:5601;
     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;
  }

   location ~ /\. {    
      deny all;  
   }
   
   ...
}

What I'm trying to do here is be able to access Kibana like http://localhost/app/kibana. The articles I've gone through (like this) seem to be focused more on securing Kibana access through NginX (using Basic Auth) rather than the ability to access on a particular path on port 80.

Update

So, I changed localhost to kibana (as suggested by @mikezter) and now it seems to be able to at least find the Kibana service (so there's no more 502 error).

However, then I encountered a blank page with a few errors in browser debug console. Upon searching, I came across this location directive:

location ~ (/app|/translations|/node_modules|/built_assets/|/bundles|/es_admin|/plugins|/api|/ui|/elasticsearch|/spaces/enter) {
         proxy_pass          http://kibana:5601;
         proxy_set_header    Host $host;
         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-Host $http_host;
         proxy_set_header    Authorization "";
         proxy_hide_header   Authorization;
  }

Now the page loads and there is some UI, but there's still some issue with the scripting, so the page is not available for user interaction.

Answer 1

You are connecting all the containers in this config via container network. Look at the environment variables set in the Kibana config:

      ELASTICSEARCH_URL: http://elasticsearch_1:9200

Here you can see, that the hostname of the other container running ElasticSearch is elasticsearch_1. In a similar manner, the hostname of the container running Kibana woud be kibana. These hostnames are only availiable inside the container network.

So in your Nginx config, you'll have to proxy_pass to http://kibana:5601 instead of localhost.