Upgrade Docker Enterprise¶

Cluster upgrade best practices¶

Mirantis Container Runtime upgrades in Swarm clusters should follow these guidelines in order to avoid IP address space exhaustion and associated application downtime.

• New workloads should not be actively scheduled in the cluster during upgrades.
• Differences in the major (X.y.z.) or minor (x.Y.z) version numbers between the managers and workers can cause unintended consequences when new workloads are scheduled.
• Manager nodes should all be upgraded first before upgrading worker nodes. Upgrading manager nodes sequentially is recommended if live workloads are running in the cluster during the upgrade.
• Once manager nodes are upgraded worker nodes should be upgraded next and then the Swarm cluster upgrade is complete.
• If running MKE, the MKE upgrade should follow once all of the Swarm engines have been upgraded.

Create a backup¶

Before upgrading Mirantis Container Runtime, you should make sure you create a backup. This makes it possible to recover if anything goes wrong during the upgrade.

Check the compatibility matrix¶

You should also check the compatibility matrix, to make sure all Mirantis Container Runtime components are certified to work with one another. You may also want to check the Mirantis Container Runtime maintenance lifecycle, to understand until when your version may be supported.

Apply firewall rules¶

Before you upgrade, make sure:

• Your firewall rules are configured to allow traffic in the ports MKE uses for communication. Learn about MKE port requirements.

• Make sure you don’t have containers or services that are listening on ports used by MKE.

• Configure your load balancer to forward TCP traffic to the Kubernetes API server port (6443/TCP by default) running on manager nodes.

  Externally signed certificates are used by the Kubernetes API server and the MKE controller.

IP address consumption in 18.09+¶

In Swarm overlay networks, each task connected to a network consumes an IP address on that network. Swarm networks have a finite amount of IPs based on the --subnet configured when the network is created. If no subnet is specified then Swarm defaults to a /24 network with 254 available IP addresses. When the IP space of a network is fully consumed, Swarm tasks can no longer be scheduled on that network.

Starting with Mirantis Container Runtime 18.09 and later, each Swarm node will consume an IP address from every Swarm network. This IP address is consumed by the Swarm internal load balancer on the network. Swarm networks running on MCR versions 18.09 or greater must be configured to account for this increase in IP usage. Networks at or near consumption prior to engine version 18.09 may have a risk of reaching full utilization that will prevent tasks from being scheduled on to the network.

Maximum IP consumption per network at any given moment follows the following formula:

Max IP Consumed per Network = Number of Tasks on a Swarm Network + 1 IP for each node where these tasks are scheduled

To prevent this from happening, overlay networks should have enough capacity prior to an upgrade to 18.09, such that the network will have enough capacity after the upgrade. The below instructions offer tooling and steps to ensure capacity is measured before performing an upgrade.

The above following only applies to containers running on Swarm overlay networks. This does not impact bridge, macvlan, host, or 3rd party docker networks.

Upgrade Mirantis Container Runtime¶

To avoid application downtime, you should be running Mirantis Container Runtime in Swarm mode and deploying your workloads as Docker services. That way you can drain the nodes of any workloads before starting the upgrade.

If you have workloads running as containers as opposed to swarm services, make sure they are configured with a restart policy. This ensures that your containers are started automatically after the upgrade.

To ensure that workloads running as Swarm services have no downtime, you need to:

1. Determine if the network is in danger of exhaustion; and remediate to a new, larger network prior to upgrading.
2. Drain the node you want to upgrade so that services get scheduled in another node.
3. Upgrade the Mirantis Container Runtime on that node.
4. Make the node available again.

If you do this sequentially for every node, you can upgrade with no application downtime. When upgrading manager nodes, make sure the upgrade of a node finishes before you start upgrading the next node. Upgrading multiple manager nodes at the same time can lead to a loss of quorum, and possible data loss.

$ docker run -it --rm -v /var/run/docker.sock:/var/run/docker.sock docker/ip-util-check

Overlay IP Utilization Report
   ----
   Network ex_net1/XXXXXXXXXXXX has an IP address capacity of 29 and uses 28 addresses
           ERROR: network will be over capacity if upgrading Docker engine version 18.09
                  or later.
   ----
   Network ex_net2/YYYYYYYYYYYY has an IP address capacity of 29 and uses 24 addresses
           WARNING: network could exhaust IP addresses if the cluster scales to 5 or more nodes
   ----
   Network ex_net3/ZZZZZZZZZZZZ has an IP address capacity of 61 and uses 52 addresses
           WARNING: network could exhaust IP addresses if the cluster scales to 9 or more nodes

ID                  NAME                MODE                REPLICAS   IMAGE               PORTS
wn3x4lu9cnln        ex_service          replicated          19/24      nginx:latest

ID                  NAME                IMAGE               NODE                DESIRED STATE       CURRENT STATE              ERROR               PORTS
    ...
i64lee19ia6s         \_ ex_service.11   nginx:latest        tk1706-ubuntu-1     Shutdown            Rejected 7 minutes ago     "node is missing network attac…"
    ...

...
            "Status": {
                "Timestamp": "2018-08-24T21:03:37.885405884Z",
                "State": "rejected",
                "Message": "preparing",
                **"Err": "node is missing network attachments, ip addresses may be exhausted",**
                "ContainerStatus": {
                    "ContainerID": "",
                    "PID": 0,
                    "ExitCode": 0
                },
                "PortStatus": {}
            },
    ...

$ docker node update --availability drain <node>