Under the hood - how Ingress gets traffic directed to containers If the service is removed (or a published port gets unpublished), then again, all participants get to know the change in the overall state and then reflect such changes in their local IPVS configuration. If it happens that the nginx container dies and the scheduler (Docker Swarm) creates a task for placing the container somewhere else, or it happens that we have a scale out situation (increasing the number of replicas to two, for instance), all machines become aware of that and update their IPVS configurations. Having a port published ( target=80,published=8000), Swarm proceeds with the configuration of the routing mesh, which happens at two moments:Īt the time that the service gets created, all participating nodes in the cluster set up their IPVS configuration to have a virtual server listening on port 8000.Īt the moment the task lands in a node and a container is created, then all machines update their IPVS configuration again, but now to include a real server that corresponds to the machine in which the container landed, forming the mesh.Įach machine now has the published port ( 8000) set to listen for incoming connections so that you can target any of them and have the connection adequately established to a container. Once the service is pushed to a Docker Swarm manager, it gets the service instantiated in the form of tasks - only one in this case ( replicas = 1)-, which turns into a container in a machine chosen by the manager. Version : '3.2' services : nginx : image : 'nginx:alpine' ports : - '8000:80' deploy : replicas : 1Īnd that we have three machines: worker-1, worker-2 and manager. Given a cluster of machines, whenever a service publishes a port, any machine can be targetted at such port, and an internal load-balancer ( IPVS) will send the traffic to a host containing an instance of such service.įor instance, assume that we have the following service definition: The ingress load-balancing setup lifecycle In this blog post, I go through what are the fundamental blocks that the routing mesh uses under the hood so we can block such kind of traffic on specific machines. When Docker Swarm mode got announced, one of the big features included was the routing mesh.Īlthough the feature indeed works as expected, there’s the possibility that you might not want to have all of your nodes accepting connections and performing the job of a load-balancer. Blocking ingress traffic to Docker swarm worker machines | OpsTips Blocking ingress traffic to Docker swarm worker machines Once a Docker Swarm Mode cluster is formed, all nodes participate in the routing mesh and accept ingress traffic.
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January 2023
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