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adding_hosts_to_existing_cluster.adoc

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Adding Hosts to an Existing Cluster

Adding etcd Hosts to existing cluster

You can add new etcd hosts to your cluster by running the etcd scaleup playbook. This playbook queries the master, generates and distributes new certificates for the new hosts, and then runs the configuration playbooks on the new hosts only. Before running the etcd scaleup.yml playbook, complete all prerequisite host preparation steps.

To add an etcd host to an existing cluster:

  1. Ensure you have the latest playbooks by updating the atomic-openshift-utils package:

    $ yum update atomic-openshift-utils

  2. Edit your /etc/ansible/hosts file, add new_<host_type> to the [OSEv3:children] group and add hosts under the new_<host_type> group:

    For example, to add a new etcd, add new_etcd:

    [OSEv3:children]
masters
nodes
etcd
new_etcd

[etcd]
etcd1.example.com
etcd2.example.com

[new_etcd]
etcd3.example.com

  3. Run the etcd scaleup.yml playbook. If your inventory file is located somewhere other than the default of /etc/ansible/hosts, specify the location with the -i option.

    $ ansible-playbook [-i /path/to/file] \
  /usr/share/ansible/openshift-ansible/playbooks/openshift-etcd/scaleup.yml

  4. After the playbook completes successfully, verify the installation.

Replacing existing masters with etcd colocated

Follow these steps when you are migrating your machines to a different data center and the network and IPs assigned to it will change.

  1. Back up the primary etcd and master nodes.

    Important

    Ensure that you back up the /etc/etcd/ directory, as noted in the etcd backup instructions.

  2. Provision as many new machines as there are masters to replace.

  3. Add or expand the cluster. for example, if you want to add 3 masters with etcd colocated, scale up 3 master nodes or 3 etcd nodes.

    1. Add a master. In step 3 of that process, add the host of the new data center in [new_masters] and [new_nodes] and run the master scaleup.yml playbook.

    2. Put the same host in the etcd section and run the etcd scaleup.yml playbook.

    3. Verify that the host was added:

      # oc get nodes

    4. Verify that the master host IP was added:

      # oc get ep kubernetes

    5. Verify that etcd was added. The value of ETCDCTL_API depends on the version being used:

      # source /etc/etcd/etcd.conf
# ETCDCTL_API=2 etcdctl --cert-file=$ETCD_PEER_CERT_FILE --key-file=$ETCD_PEER_KEY_FILE \
  --ca-file=/etc/etcd/ca.crt --endpoints=$ETCD_LISTEN_CLIENT_URLS member list

    6. Copy /etc/origin/master/ca.serial.txt from the /etc/origin/master directory to the new master host that is listed first in your inventory file. By default, this is /etc/ansible/hosts.

  4. Remove the etcd hosts.

    1. Copy the /etc/etcd/ca directory to the new etcd host that is listed first in your inventory file. By default, this is /etc/ansible/hosts.

    2. Remove the old etcd clients from the master-config.yaml file:

      # grep etcdClientInfo -A 11 /etc/origin/master/master-config.yaml

    3. Restart the masters:

      # systemctl restart atomic-openshift-master-*

    4. Remove the old etcd members from the cluster. The value of ETCDCTL_API depends on the version being used:

      # source /etc/etcd/etcd.conf
# ETCDCTL_API=2 etcdctl --cert-file=$ETCD_PEER_CERT_FILE --key-file=$ETCD_PEER_KEY_FILE \
  --ca-file=/etc/etcd/ca.crt --endpoints=$ETCD_LISTEN_CLIENT_URLS member list

    5. Take the IDs from the output of the command above and remove the old members using the IDs:

      # etcdctl --cert-file=$ETCD_PEER_CERT_FILE --key-file=$ETCD_PEER_KEY_FILE \
  --ca-file=/etc/etcd/ca.crt --endpoints=$ETCD_LISTEN_CLIENT_URL member remove 1609b5a3a078c227

    6. Stop and disable the etcd services on the old etcd hosts:

      # systemctl stop etcd
# systemctl disable etcd

  5. Shut down old master API and controller services:

    # systemctl stop atomic-openshift-master-api

  6. Remove the master nodes from the HA proxy configuration, which was installed as a load balancer by default during the native installation process.

  7. Decommission the machine.

    1. Stop the atomic-openshift-node service on the master to be removed:

      # systemctl stop atomic-openshift-node

    2. Delete the node resource:

      # oc delete node

Migrating the nodes

You can migrate nodes individually or in groups (of 2, 5, 10, and so on), depending on what you are comfortable with and how the services on the node are run and scaled.

  1. For the migration node or nodes, provision new VMs for the node’s use in the new data center.

  2. To add the new node, scale up the infrastructure. Ensure the labels for the new node are set properly and that your new API servers are added to your load balancer and successfully serving traffic.

  3. Evaluate and scale down.

    1. Mark the current node (in the old data center) unscheduled.

    2. Evacuate the node, so that pods on it are scheduled to other nodes.

    3. Verify that the evacuated services are running on the new nodes.

  4. Remove the node.

    1. Verify that the node is empty and does not have running processes.

    2. Stop the service or delete the node.