Draining a Node in a Docker Swarm

--- description: Drain nodes on the swarm keywords: tutorial, cluster management, swarm, service, drain, get started title: Drain a node on the swarm weight: 80 notoc: true --- In earlier steps of the tutorial, all the nodes have been running with `Active` availability. The swarm manager can assign tasks to any `Active` node, so up to now all nodes have been available to receive tasks. Sometimes, such as planned maintenance times, you need to set a node to `Drain` availability. `Drain` availability prevents a node from receiving new tasks from the swarm manager. It also means the manager stops tasks running on the node and launches replica tasks on a node with `Active` availability. > > Setting a node to `Drain` does not remove standalone containers from that node, > such as those created with `docker run`, `docker compose up`, or the Docker Engine > API. A node's status, including `Drain`, only affects the node's ability to schedule > swarm service workloads. 1. If you haven't already, open a terminal and ssh into the machine where you run your manager node. For example, the tutorial uses a machine named `manager1`. 2. Verify that all your nodes are actively available. ```console $ docker node ls ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS 1bcef6utixb0l0ca7gxuivsj0 worker2 Ready Active 38ciaotwjuritcdtn9npbnkuz worker1 Ready Active e216jshn25ckzbvmwlnh5jr3g * manager1 Ready Active Leader ``` 3. If you aren't still running the `redis` service from the [rolling update](rolling-update.md) tutorial, start it now: ```console $ docker service create --replicas 3 --name redis --update-delay 10s redis:7.4.0 c5uo6kdmzpon37mgj9mwglcfw ``` 4. Run `docker service ps redis` to see how the swarm manager assigned the tasks to different nodes: ```console $ docker service ps redis NAME IMAGE NODE DESIRED STATE CURRENT STATE redis.1.7q92v0nr1hcgts2amcjyqg3pq redis:7.4.0 manager1 Running Running 26 seconds redis.2.7h2l8h3q3wqy5f66hlv9ddmi6 redis:7.4.0 worker1 Running Running 26 seconds redis.3.9bg7cezvedmkgg6c8yzvbhwsd redis:7.4.0 worker2 Running Running 26 seconds ``` In this case the swarm manager distributed one task to each node. You may

This section explains how to drain a node in a Docker Swarm. Draining a node prevents it from receiving new tasks and migrates existing tasks to active nodes. The tutorial guides you through setting a node to `Drain` availability, observing task redistribution, and verifying the change using `docker node ls` and `docker service ps` commands. It also clarifies that draining a node only affects swarm service workloads and not standalone containers.