instruction: Create a comprehensive Dockerfile for networking applications with best practices
output: ```dockerfile
  from Docker Hub or the private registry.If it succeeds, the task is deployed using the new image.If the worker fails to pull the image, the service fails to deploy on that
  worker node. Docker tries again to deploy the task, possibly on a different
  worker node.If the manager cannot resolve the tagIf the swarm manager cannot resolve the image to a digest, all is not lost:The manager instructs the worker nodes to redeploy the tasks using the image
  at that tag.If the worker has a locally cached image that resolves to that tag, it uses
  that image.If the worker does not have a locally cached image that resolves to the tag,
  the worker tries to connect to Docker Hub or the private registry to pull the
  image at that tag.If this succeeds, the worker uses that image.If this fails, the task fails to deploy and the manager tries again to deploy
  the task, possibly on a different worker node.Publish portsWhen you create a swarm service, you can publish that service's ports to hosts
  outside the swarm in two ways:You can rely on the routing mesh.
  When you publish a service port, the swarm makes the service accessible at the
  target port on every node, regardless of whether there is a task for the
  service running on that node or not. This is less complex and is the right
  choice for many types of services.You can publish a service task's port directly on the swarm node
  where that service is running. This bypasses the routing mesh and provides the
  maximum flexibility, including the ability for you to develop your own routing
  framework. However, you are responsible for keeping track of where each task is
  running and routing requests to the tasks, and load-balancing across the nodes.Keep reading for more information and use cases for each of these methods.Publish a service's ports using the routing meshTo publish a service's ports externally to the swarm, use the
  --publish <PUBLISHED-PORT>:<SERVICE-PORT> flag. The swarm makes the service
  accessible at the published port on every swarm node. If an external host
  connects to that port on any swarm node, the routing mesh routes it to a task.
  The external host does not need to know the IP addresses or internally-used
  ports of the service tasks to interact with the service. When a user or process
  connects to a service, any worker node running a service task may respond. For
  more details about swarm service networking, see
  Manage swarm service networks.Example: Run a three-task Nginx service on 10-node swarmImagine that you have a 10-node swarm, and you deploy an Nginx service running
  three tasks on a 10-node swarm:
  
  $ docker service create --name my_web \
   --replicas 3 \
   --publish published=8080,target=80 \
   nginx
  Three tasks run on up to three nodes. You don't need to know which nodes
  are running the tasks; connecting to port 8080 on any of the 10 nodes
  connects you to one of the three nginx tasks. You can test this using curl.
  The following example assumes that localhost is one of the swarm nodes. If
  this is not the case, or localhost does not resolve to an IP address on your
  host, substitute the host's IP address or resolvable host name.The HTML output is truncated:
  
  $ curl localhost:8080
  
  <!DOCTYPE html>
  <html>
  <head>
  <title>Welcome to nginx!</title>
  ...truncated...
  </html>
  Subsequent connections may be routed to the same swarm node or a different one.Publish a service's ports directly on the swarm nodeUsing the routing mesh may not be the right choice for your application if you
  need to make routing decisions based on application state or you need total
  control of the process for routing requests to your service's tasks. To publish
  a service's port directly on the node where it is running, use the mode=host
  option to the --publish flag.
  NoteIf you publish a service's ports directly on the swarm node using
  mode=host and also set published=<PORT> this creates an implicit
  limitation that you can only run one task for that service on a given swarm
  node. You can work around this by specifying published without a port
  definition, which causes Docker to assign a random port for each task.In addition, if you use mode=host and you do not use the
  --mode=global flag on docker service create, it is difficult to know
  which nodes are running the service to route work to them.Example: Run an nginx web server service on every swarm nodenginx is an open source reverse proxy, load
  balancer, HTTP cache, and a web server. If you run nginx as a service using the
  routing mesh, connecting to the nginx port on any swarm node shows you the
  web page for (effectively) a random swarm node running the service.The following example runs nginx as a service on each node in your swarm and
  exposes nginx port locally on each swarm node.
  
  $ docker service create \
   --mode global \
   --publish mode=host,target=80,published=8080 \
   --name=nginx \
   nginx:latest
  You can reach the nginx server on port 8080 of every swarm node. If you add a
  node to the swarm, a nginx task is started on it. You cannot start another
  service or container on any swarm node which binds to port 8080.
  NoteThis is a purely illustrative example. Creating an application-layer
  routing framework for a multi-tiered service is complex and out of scope for
  this topic.Connect the service to an overlay networkYou can use overlay networks to connect one or more services within the swarm.First, create overlay network on a manager node using the docker network create
  command with the --driver overlay flag.
  
  $ docker network create --driver overlay my-network
  After you create an overlay network in swarm mode, all manager nodes have access
  to the network.You can create a new service and pass the --network flag to attach the service
  to the overlay network:
  
  $ docker service create \
   --replicas 3 \
   --network my-network \
   --name my-web \
   nginx
  The swarm extends my-network to each node running the service.You can also connect an existing service to an overlay network using the
  --network-add flag.
  
  $ docker service update --network-add my-network my-web
  To disconnect a running service
  ```