Amazon DOP-C01 Practice Test - Questions Answers, Page 20

A service is the definition of the tasks to execute on the worker nodes. It is the central structure of the swarm system and the primary root of user interaction with the swarm. When you create a service, you specify which container image to use and which commands to execute inside running containers. In the replicated services model, the swarm manager distributes a specific number of replica tasks among the nodes based upon the scale you set in the desired state. For global services, the swarm runs one task for the service on every available node in the cluster. A task carries a Docker container and the commands to run inside the container. It is the atomic scheduling unit of swarm. Manager nodes assign tasks to worker nodes according to the number of replicas set in the service scale. Once a task is assigned to a node, it cannot move to another node. It can only run on the assigned node or fail.

Reference: https://docs.docker.com/engine/swarm/key-concepts/#services-and-tasks

The high-availability feature is not a scaling solution for read-only scenarios; you cannot use a standby replica to serve read traffic. To service read-only traffic, you should use a Read Replica. For more information, see Working with PostgreSQL, MySQL, and MariaDB Read Replicas.

Reference: http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html

We use the variable's name to reference the variable which we encapsulate in curly brackets `{{ }}'; however, the YAML syntax dictates that a string beginning with a curly bracket denotes a dictionary value. To get around this, it is proper to wrap the variable declaration in quotes.

Reference: http://docs.ansible.com/ansible/playbooks_variables.html#hey-wait-a-yaml-gotcha

Ansible expects an inventory filename with the ‘-i’ option, regardless if it is a valid hostname. For this to execute on the host `localhost' resolves to, a comma needs to be appended to the end.

Reference: http://docs.ansible.com/ansible/intro_inventory.html#inventory

This IAM policy grants access to the ChangePassword action, which lets the users use the console, the CLI, or the API to change their passwords. The Resource element uses a policy variable (aws:username), which is useful in policies that are attached to groups. The aws:username key resolves to the name of the current IAM user when a request is made, so that each user is allowed permission to change only his or her own password . This policy will allow all the users of this group to modify the passwords of all the IAM users.

Reference: http://docs.aws.amazon.com/IAM/latest/UserGuide/HowToPwdIAMUser.html