Inter-container communication in azure container instances

Question

I'm trying to create a container instance group in azure container instances. I have two docker images : a guincorn web application server listening on an exposed port 8000, and a nginx proxy server. I am able to deploy to azure container instances, but I get the following error in my proxy container.

> nginx: [emerg] host not found in upstream "web:8000" in /etc/nginx/conf.d/nginx.conf:7

It seems like I am not configuring the container network correctly. Can someone please hint how I should configure a inter-container network on azure container instances? I build the images on my local machine, then pushed them to docker hub, and then built the container group in an ACI YAML file

I am able to get this group working on my local machine with the following configuration files → ACI .yml configuration :

name: webapp-containers
apiVersion: '2018-10-01'
location: eastus
properties: # Properties of a container group
    containers: # Array of container instances in group

    - name: web # Instance name
      properties: # Instance properties
        image: johnvorsten/my_site_web:1.08
        environmentVariables: 
              [shortened...]
            - name: WEBAPP_INTERNAL_PORT
              value: '8000'
        resources:
            requests: 
                cpu: 1
                memoryInGb: 1
        ports: # Exposed on the container instance
            - protocol: tcp
              port: '8000'

    - name: webapp-proxy
      properties:
        image: johnvorsten/my_site_nginx:1.02
        resources:
            requests:
                cpu: 1
                memoryInGb: 0.5
        environmentVariables: 
            - name: PROXY_EXTERNAL_PORT
              value: '80' # Exposed on container
            - name: PROXY_EXTERNAL_PORT_HTTPS
              value: '443' # Exposed on container
            - name: WEBAPP_INTERNAL_PORT
              value: '8000'
            - name: WEBAPP_HOSTNAME_AZURE
              value: web

        ports: # Exposed on instance
            - protocol: tcp
              port: '80'
            - protocol: tcp
              port: '443'
        volumeMounts:
        - mountPath: /home/apps/web/static-serve
          name: static-serve

    imageRegistryCredentials:
    - server: index.docker.io
      username: username
      password: password

    osType: Linux
    ipAddress:
        type: Public
        dnsNameLabel: jv-webapp-group
        ports: # Exposed in container group (external)
            - protocol: tcp
              port: '80'
            - protocol: tcp
              port: '443'

    volumes: 
    - name: static-serve
      emptyDir: {}
tags: {}
type: Microsoft.ContainerInstance/containerGroups

My nginx configuration file :

upstream upstream_server {
    server web:8000;
}

server {
    listen 80;
    listen [::]:443 ssl;
    listen 443 ssl;

    server_name localhost; # Change when deploying to production

    ssl_protocols TLSv1.2;

    ssl_ciphers [...]
    ssl_prefer_server_ciphers  on;

    ssl_session_cache    shared:SSL:1m;
    ssl_session_timeout  24h;

    keepalive_timeout 300; # up from 75 secs default

    add_header Strict-Transport-Security 'max-age=31536000; includeSubDomains';

    ssl_certificate      /etc/nginx/ssl.crt;
    ssl_certificate_key  /etc/nginx/ssl.key;

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    location / {
        proxy_pass http://upstream_server;
        proxy_set_header Connection "";

        # See ip address of client (not proxy)
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

        proxy_set_header Host $host;

        # Not sure what this is useful for
        proxy_set_header X-Forwarded-Host $server_name;
        proxy_redirect off;

        error_log  /var/log/nginx/proxy_pass_log.log;
    }

    location /static-serve/ {
        alias /home/app/web/static-serve/;
    }

} # End server

J.Vo J.Vo · Accepted Answer · 2020-03-15T16:18:06

From the MSDN :

Within a container group, container instances can reach each other via localhost on any port, even if those ports aren't exposed externally on the group's IP address or from the container

Inter-container communication in azure container instances

2 Answers