Azure Functions configuration for local Docker deployment, requires nginx reverse proxy for CORS support.

.env

# Sets the network port the container listens on at runtime for NGINX reverse proxy.
NGINX_PORT_EXPOSE=

# Sets the network port the container listens on at runtime for Azure Functions.
AZURE_FUNCTIONS_PORT_EXPOSE=

docker-compose.yml

  nginx:
    hostname: nginx
    build:
      context: .
      dockerfile: ./nginx/Dockerfile
    init: true
    environment:
      - 'AZURE_FUNCTIONS_PORT_EXPOSE=${AZURE_FUNCTIONS_PORT_EXPOSE}'
    ports: 
      - '${NGINX_PORT_EXPOSE}:80'
    healthcheck:
      test: [
        "CMD",
        "service",
        "nginx",
        "status"
      ]
      interval: 30s
      timeout: 5s
      retries: 3

Dockerfile

# Set the base image for subsequent instructions.
FROM nginx:latest

# Copy the template configuration file from the current 
# directory to inside the container.
COPY ./nginx/nginx.template /etc/nginx/conf.d/default.template

# Uses envsubst to generate configuration file dynamically
# by replacing environment variables in the template file and 
# outputting the results to the default.conf file and starts the 
# nginx server.
CMD sh -c "envsubst \"`env | \
    awk -F = '{printf \" \\\\$%s\", $1}'`\" \
    < /etc/nginx/conf.d/default.template > \
    /etc/nginx/conf.d/default.conf && \
    nginx -g 'daemon off;'"

nginx.template

# Listens on port 80 and handles requests with the server_name set
# to localhost.
server 
{
    listen       80;
    server_name  localhost;

    # Responsible for handling requests that match the specified URL path. 
    # It acts as a reverse proxy, forwarding the requests to the upstream
    # server.
    location /runtime/webhooks/durabletask/instances/
    {

        # Identifies the actual IP address of the client when requests
        # are proxied, indicate request has been forwarded by a reverse
        # proxy, and instructs the backend not to compress the response.
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-NginX-Proxy true;
        proxy_set_header Accept-Encoding "";

        # Specify the backend to which requests are forwarded.
        proxy_pass http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE};

        # Adds headers to allow cross-origin requests. For 'OPTIONS' requests,
        # there is additional logic which is used for preflight requests.
        if ($request_method = 'OPTIONS') {
            add_header 'Access-Control-Allow-Origin' "*" always;
            add_header 'Access-Control-Allow-Credentials' 'false' always;
            add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
            add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;
            add_header 'Access-Control-Max-Age' 1728000;
            add_header 'Content-Type' 'text/plain; charset=utf-8';
            add_header 'Content-Length' 0;
            return 204;
        }
        add_header 'Access-Control-Allow-Origin' "*" always;
        add_header 'Access-Control-Allow-Credentials' 'false' always;
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
        add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;

        # Modifies the response headers of the reverse proxy response, to rewrite
        # the server.
        proxy_redirect http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE}/ http://localhost:7071/;
        sub_filter_types application/json;
        sub_filter 'http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE}' 'http://localhost:7071';
        sub_filter_once off;
    }

    # Responsible for handling requests that match the specified URL path. 
    # It acts as a reverse proxy, forwarding the requests to the upstream
    # server.
    location /api/ 
    {

        # Identifies the actual IP address of the client when requests
        # are proxied, indicate request has been forwarded by a reverse
        # proxy, and instructs the backend not to compress the response.
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-NginX-Proxy true;
        proxy_set_header Accept-Encoding "";

        # Specify the backend to which requests are forwarded.
        proxy_pass http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE};
    
        # Adds headers to allow cross-origin requests. For 'OPTIONS' requests,
        # there is additional logic which is used for preflight requests.
        if ($request_method = 'OPTIONS') {
            add_header 'Access-Control-Allow-Origin' "*" always;
            add_header 'Access-Control-Allow-Credentials' 'false' always;
            add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
            add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;
            add_header 'Access-Control-Max-Age' 1728000;
            add_header 'Content-Type' 'text/plain; charset=utf-8';
            add_header 'Content-Length' 0;
            return 204;
        }
        add_header 'Access-Control-Allow-Origin' "*" always;
        add_header 'Access-Control-Allow-Credentials' 'false' always;
        add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;
        add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;

        # Modifies the response headers of the reverse proxy response, to rewrite
        # the server.
        proxy_redirect http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE}/ http://localhost:7071/;
        sub_filter_types application/json;
        sub_filter 'http://host.docker.internal:${AZURE_FUNCTIONS_PORT_EXPOSE}' 'http://localhost:7071';
        sub_filter_once off;
    }        
}