Docker Swarm & Orchestration Flashcards
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Read the first 7 Docker Swarm & Orchestration flashcards as text
What is the minimum number of manager nodes required so that a Docker Swarm can tolerate the failure of one manager?
Answer: 3
Three managers are the minimum for single-node fault tolerance because Raft requires a majority quorum (2 of 3) to remain operational.
What does the Raft consensus algorithm provide in a Docker Swarm cluster?
Answer: Consistent distributed state management across manager nodes
Raft ensures all manager nodes agree on the cluster state and can elect a new leader if the current one fails, providing a consistent and fault-tolerant control plane.
Which command sets the availability of a Swarm node named 'node1' to 'drain'?
Answer: docker node update --availability drain node1
`docker node update --availability drain node1` prevents new tasks from being scheduled on the node and reschedules existing tasks elsewhere.
What is a Docker Stack in the context of Swarm mode?
Answer: A group of interrelated services deployed together using a Compose-format file
A Docker Stack bundles multiple services defined in a Compose file and deploys them as a unit to a Swarm, enabling multi-service orchestration.
Which command deploys a stack named 'myapp' to a Swarm using 'docker-compose.yml'?
Answer: docker stack deploy -c docker-compose.yml myapp
`docker stack deploy -c docker-compose.yml myapp` reads the Compose file and deploys the defined services as a stack to the active Swarm.
What happens to a node's ability to run service tasks after it is promoted from worker to manager in Docker Swarm?
Answer: The node continues running tasks while also performing management functions
Manager nodes participate in task scheduling by default and can run service tasks unless their availability is explicitly set to 'drain'.
What is a service 'placement constraint' in Docker Swarm?
Answer: A rule that restricts which nodes are eligible to run a service's tasks
Placement constraints use node labels or built-in node properties to filter which nodes the Swarm scheduler may use when placing tasks for a service.
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