Apply rolling updates to a service (original) (raw)

In a previous step of the tutorial, you scaled the number of instances of a service. In this part of the tutorial, you deploy a service based on the Redis 7.4.0 container tag. Then you upgrade the service to use the Redis 7.4.1 container image using rolling updates.

• 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 namedmanager1.
• Deploy your Redis tag to the swarm and configure the swarm with a 10 second update delay. Note that the following example shows an older Redis tag:
  You configure the rolling update policy at service deployment time.
  The --update-delay flag configures the time delay between updates to a service task or sets of tasks. You can describe the time T as a combination of the number of seconds Ts, minutes Tm, or hours Th. So10m30s indicates a 10 minute 30 second delay.
  By default the scheduler updates 1 task at a time. You can pass the--update-parallelism flag to configure the maximum number of service tasks that the scheduler updates simultaneously.
  By default, when an update to an individual task returns a state ofRUNNING, the scheduler schedules another task to update until all tasks are updated. If at any time during an update a task returns FAILED, the scheduler pauses the update. You can control the behavior using the--update-failure-action flag for docker service create ordocker service update.
• Inspect the redis service:
• Now you can update the container image for redis. The swarm manager applies the update to nodes according to the UpdateConfig policy:
  The scheduler applies rolling updates as follows by default:
• Stop the first task.
• Schedule update for the stopped task.
• Start the container for the updated task.
• If the update to a task returns RUNNING, wait for the specified delay period then start the next task.
• If, at any time during the update, a task returns FAILED, pause the update.
• Run docker service inspect --pretty redis to see the new image in the desired state:
  The output of service inspect shows if your update paused due to failure:
  To restart a paused update run docker service update <SERVICE-ID>. For example:
  To avoid repeating certain update failures, you may need to reconfigure the service by passing flags to docker service update.
• Run docker service ps <SERVICE-ID> to watch the rolling update:
  Before Swarm updates all of the tasks, you can see that some are runningredis:7.4.0 while others are running redis:7.4.1. The output above shows the state once the rolling updates are done.

Next, you'll learn how to drain a node in the swarm.