Docker Updated DCA Exam Questions and Answers by navy

 A node is a physical or virtual machine running Docker Engine in swarm mode1. A node can be either a manager or a worker, depending on its role in the cluster1. A physical machine participating in the swarm is a node, regardless of its role or availability2. References:

• How nodes work | Docker Docs
• Manage nodes in a swarm | Docker Docs

The set of commands docker container inspect and docker port can identify the published port(s) for a container. The docker container inspect command returns low-level information about a container, including its network settings and port bindings1. The docker port command lists port mappings or a specific mapping for the container2. Both commands can show which host port is mapped to which container port, and the protocol used. For example, docker container inspect -f '{{.NetworkSettings.Ports}}' container_name will show the port bindings for the container_name3. Similarly, docker port container_name will show the port mappings for the container_name. References:

• docker container inspect
• docker port
• How to Expose and Publish Ports in Docker
• [How to obtain the published ports from within a docker container?]

= The command kubectl events deployment api is not a valid kubectl command. The correct command to display the events for a deployment object is kubectl get events --field-selector involvedObject.name=api12. This command uses a field selector to filter the events by the name of the involved object, which is the deployment called api. Alternatively, you can use kubectl describe deployment api to see the details and the events for the deployment3. References:

• 1: kubectl Cheat Sheet | Kubernetes
• 2: kubernetes - kubectl get events only for a pod - Stack Overflow
• 3: Kubectl: Get Events & Sort By Time - ShellHacks

= Distributing seven managers across three datacenters or availability zones as 3-3-1 is not the best way to ensure high availability and fault tolerance. This is because if one of the datacenters with three managers fails, the remaining four managers will not have a quorum to elect a leader and continue the swarm operations. A quorum is the minimum number of managers that must be available to maintain the swarm state, and it is calculated as (N/2) + 1, where N is the total number of managers1. For seven managers, the quorum is five, so losing three managers will cause the swarm to lose the quorum. A better way to distribute seven managers across three datacenters or availability zones is 2-2-3, which will allow the swarm to survive the failure of any one datacenter2. References:

• Administer and maintain a swarm of Docker Engines
• Distribute manager nodes across multiple AZ