These steps are given in the AWS documentation
To migrate data between encrypted and unencrypted volumes
1) Create your destination volume (encrypted or unencrypted, depending on your need).
2) Attach the destination volume to the instance that hosts the data to migrate.
3) Make the destination volume available by following the procedures in Making an Amazon EBS Volume Available for Use. For Linux instances, you can create a mount point at /mnt/destination and mount the destination volume there.
4) Copy the data from your source directory to the destination volume. It may be most convenient to use a bulk-copy utility for this.
To encrypt a volume's data by means of snapshot copying
1) Create a snapshot of your unencrypted CBS volume. This snapshot is also unencrypted.
2) Copy the snapshot while applying encryption parameters. The resulting target snapshot is encrypted.
3) Restore the encrypted snapshot to a new volume, which is also encrypted.
For more information on EBS Encryption, please refer to the below document link: from AWS
http://docs.aws.a mazon.com/AWSEC2/latest/UserGuide/ EBSEncryption.html

These steps are given in the AWS documentation
To migrate data between encrypted and unencrypted volumes
1) Create your destination volume (encrypted or unencrypted, depending on your need).
2) Attach the destination volume to the instance that hosts the data to migrate.
3) Make the destination volume available by following the procedures in Making an Amazon EBS Volume Available for Use. For Linux instances, you can create a mount point at /mnt/destination and mount the destination volume there.
4) Copy the data from your source directory to the destination volume. It may be most convenient to use a bulk-copy utility for this.
To encrypt a volume's data by means of snapshot copying
1) Create a snapshot of your unencrypted CBS volume. This snapshot is also unencrypted.
2) Copy the snapshot while applying encryption parameters. The resulting target snapshot is encrypted.
3) Restore the encrypted snapshot to a new volume, which is also encrypted.
For more information on EBS Encryption, please refer to the below document link: from AWS
http://docs.aws.a mazon.com/AWSEC2/latest/UserGuide/ EBSEncryption.html

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

Explanation
In Rolling deployment, you can mention a new set of servers which can replace the existing set of servers.
This replacement will happen in a phased out manner.
Since there is a requirement to not swap URL's, you must not use Blue Green deployments.
For more information on the differences between Rolling Updates and Blue Green deployments, please refer
to the below URL:
* https://cloudnative.io/docs/blue-green-deployment/