High Availability: Backend Cluster¶

This topic describes the process of upgrading a highly available Chef server cluster.

Note

This feature is included as part of the Chef Automate license agreement and is available via subscription.

Overview¶

These instructions cover the process of upgrading a Chef Backend cluster. Please refer to the appropriate directions for the version of Chef Backend you are using, and the version you intend to upgrade to:

Chef Backend 1.x to 2.x Upgrade (downtime upgrade)
Chef Backend 1.x to 1.x Upgrade (rolling upgrade)

Chef Backend 1.x to 2.x Upgrade¶

Warning

Upgrading from Chef Backend 1.x to Chef Backend 2.x requires full cluster downtime.

Identify the node with the leader role using the chef-backend-ctl cluster-status command:

Name       IP              GUID                              Role      PG        ES
backend-1  192.168.33.215  dc0c6ea77a751f94037cd950e8451fa3  leader    leader    not_master
backend-2  192.168.33.216  008782c59d3628b6bb7f43556ac0c66c  follower  follower  not_master
backend-3  192.168.33.217  1af654172b1830927a571d9a5ba7965b  follower  follower  master

In this example, backend-1 is the leader node, as indicated by its role in the Role column.

Install the new Chef Backend package on all nodes in the cluster:
- RHEL and CentOS:
```
yum install PATH_TO_FILE.rpm
```
- Debian and Ubuntu:
```
dpkg -i PATH_TO_FILE.deb
```
On the leader, run the following command to take the node down for the upgrade:
```
chef-backend-ctl down-for-upgrade
```
Then issue the same command on the follower nodes:
```
chef-backend-ctl down-for-upgrade
```
Initiate the upgrade on the follower nodes first:
```
chef-backend-ctl upgrade
```
Then initiate the upgrade on the leader node:
```
chef-backend-ctl upgrade
```
On any Chef Server frontend nodes using the Chef Backend cluster upgraded in the previous steps, run:
```
chef-server-ctl reconfigure
```
To continue the upgrades on Chef Server frontends using this backend cluster, see Upgrade Frontends Associated with a Chef Backend Cluster

Chef Backend 1.x to 1.x Upgrade¶

Note

The procedure assumes that the new chef-backend package has been copied to all of the nodes.

Step 1: Block Failover¶

We don’t want the cluster to fail over to a follower that is in the process of being upgraded. So we start by disabling failover

Run chef-backend-ctl set-cluster-failover off

Step 2: Upgrade the followers.¶

Followers should be upgraded sequentially. Upgrading them simultaneously is not supported and may result in data loss. Verify the successful rejoin after each upgrade.

Install the new chef-backend package
- In RedHat/CentOS: yum install PATH_TO_RPM
- In Debian/Ubuntu: dpkg -i PATH_TO_DEB

You may also want to look at the chef-ingredient cookbook to automate downloading and installing the latest package.

Run the upgrade command
```
% chef-backend-ctl upgrade
```

The upgrade command will make any changes necessary to start the new service and verify that the upgraded node has rejoined the cluster.

Repeat the previous steps in this section for each remaining follower.

Step 3: Upgrade the leader¶

Unblock failover, trigger failover, block it again.

% chef-backend-ctl set-cluster-failover on
% chef-backend-ctl upgrade --failover
% chef-backend-ctl set-cluster-failover off

Step 4: Re-enable failover¶

Allow failover again:

% chef-backend-ctl set-cluster-failover on

Step 5: Verify the cluster is stable¶

Check the status of the cluster:

% chef-backend-ctl status