Configure high availability

To configure high availability, you must provision and enable a replica to serve as backup during failovers. If your master is permanently disabled, you can then promote a replica.

Before you begin

Apply high availability system and software requirements.

Tip: High availability is configured and managed with puppet infrastructure commands, many of which require a valid admin RBAC token. For details about these commands, on the command line, run puppet infrastructure help <ACTION>, for example, puppet infrastructure help provision.

Provision a replica

Provisioning a replica duplicates specific components and services from the master to the replica.

Before you begin

Ensure you have a valid admin RBAC token.

Note: While completing this task, the master is unavailable to serve catalog requests. Time completing this task accordingly.

Ensure that the node you're provisioning as a replica is set to use the primary master as its Puppet Server.
On the prospective replica node, in the /etc/puppetlabs/puppet/puppet.conf file's main section, set the server variable to the node name of the primary master. For example:
```
[main]
certname = <REPLICA NODE NAME> 
server = <MASTER NODE NAME>
```
On the primary master, as the root user, run puppet infrastructure provision replica <REPLICA NODE NAME>
After the provision command completes, services begin syncing from the master to the replica. The amount of time the sync takes depends on the size of your PuppetDB and the capability of your hardware. Typical installations take 10-30 minutes. With large data sets, you can optionally do a manual PuppetDB replication to speed installation.

Note: All puppet infrastructure commands must be run from a root session. Running with elevated privileges via sudo puppet infrastructure is not sufficient. Instead, start a root session by running sudo su -, and then run the puppet infrastructure command.
(Optional) Verify that all services running on the primary master are also running on the replica:
1. From the primary master, run puppet infrastructure status --verbose to verify that the replica is available.
2. From any managed node, run puppet agent -t --noop --server_list=<REPLICA HOSTNAME>. If the replica is correctly configured, the Puppet run succeeds and shows no changed resources.

When provisioning is complete, you must enable the replica to complete your HA configuration.

Manually copy PuppetDB to speed replication

For large PuppetDB installations, you can speed initial replication by manually copying the database from the master to the replica. If you have already started automatic provisioning, you can manually copy your PuppetDB at any time during sync.

The size of your PuppetDB correlates with the number of nodes and resources in your Puppet catalogs. To optionally examine the size of your database, on the PuppetDB PostgreSQL node, run sudo -u pe-postgres /opt/puppetlabs/server/bin/psql -c '\l+ "<DB_NAME>"'.

Note: By default, <DB_NAME> is pe-puppetdb.

On the PuppetDB node, export the database:

sudo -u pe-postgres /opt/puppetlabs/server/bin/pg_dump --format=custom --compress=3 --file=<DUMP_OUTPUT> --dbname="<DB_NAME>"

On the PuppetDB node, transfer the output using your preferred tool, such as SCP:
```
scp -r <DUMP_OUTPUT> <REMOTE_USER>@<REPLICA_HOST>:<REPLICA_DUMP_OUTPUT>
```

On the primary replica node, restore PuppetDB:

sudo puppet resource service puppet ensure=stopped
sudo puppet resource service pe-puppetdb ensure=stopped
sudo -u pe-postgres /opt/puppetlabs/server/bin/pg_restore --clean --jobs=<PROCESSOR_COUNT> --dbname="<DB_NAME>" <REPLICA_DUMP_OUTPUT>
sudo puppet resource service puppet ensure=running
sudo puppet resource service pe-puppetdb ensure=running
sudo puppet agent -t

After manual export and restore, PuppetDB automatically updates the replica with any changes that occurred on the master in the meantime.

Enable a replica

Enabling a replica activates most of its duplicated services and components, and instructs agents and infrastructure nodes how to communicate in a failover scenario.

Before you begin

Back up your classifier hierarchy, because enabling a replica alters classification.
Ensure you have a valid admin RBAC token.

Note: While completing this task, the master is unavailable to serve catalog requests. Time completing this task accordingly.

On the primary master, as the root user, run puppet infrastructure enable replica <REPLICA NODE NAME>, then follow the prompts to instruct Puppet how to configure your deployment.
Deploy updated configuration to nodes by running Puppet or waiting for the next scheduled Puppet run.

Note: If you use the direct Puppet workflow, where agents use cached catalogs, you must manually deploy the new configuration by running puppet job run --no-enforce-environment --query 'nodes {deactivated is null and expired is null}'
Optional: Perform any tests you feel are necessary to verify that Puppet runs continue to work during failover. For example, to simulate an outage on the master:
1. Prevent the replica and a test node from contacting the master. For example, you might temporarily shut down the master or use iptables with drop mode.
2. Run puppet agent -t on the test node. If the replica is correctly configured, the Puppet run succeeds and shows no changed resources. Runs may take longer than normal when in failover mode.
3. Reconnect the replica and test node.
On the replica, in the /etc/puppetlabs/puppet/puppet.conf file's main section, remove the entire line where the server variable is set: server = <MASTER NODE NAME>
When you enable HA, the server variable is superseded by the server_list variable. If you later promote a replica on which the server variable still exists and points to the old master, some commands might not function properly.
If you've specified any tuning parameters for your master using the console, move them to Hiera instead.
Using Hiera ensures configuration is applied to both your master and replica.

Managing agent communication in geo-diverse installations

Typically, when you enable a replica using puppet infrastructure enable replica, the configuration tool automatically sets the same communication parameters for all agents. In geo-diverse installations, with load balancers or compile masters in multiple locations, you must manually configure agent communication settings so that agents fail over to the appropriate load balancer or compile master.

To skip automatically configuring which Puppet servers and PCP brokers agents communicate with, use the --skip-agent-config flag when you enable a replica, for example:

puppet infrastructure enable replica example.puppet.com --skip-agent-config

To manually configure which load balancer or compile master agents communicate with, use one of these options:

CSR attributes
1. For each node, include a CSR attribute that identifies the location of the node, for example pp_region or pp_datacenter.
2. Create child groups off of the PE Agent node group for each location.
3. In each child node group, include the puppet_enterprise::profile::agent module and set the server_list parameter to the appropriate load balancer or compile master hostname.
4. In each child node group, add a rule that uses the trusted fact created from the CSR attribute.
Hiera
For each node or group of nodes, create a key/value pair that sets the puppet_enterprise::profile::agent::server_list parameter to be used by the PE Agent node group.
Custom method that sets the server_list parameter in puppet.conf.

Promote a replica

If your master can’t be restored, you can promote the replica to master to establish the replica as the new, permanent master.

Verify that the primary master is permanently offline.
If the primary master comes back online during promotion, your agents can get confused trying to connect to two active masters.
On the replica, as the root user, run puppet infrastructure promote replica
Promotion can take up to the amount of time it took to install PE initially. Don’t make code or classification changes during or after promotion.
When promotion is complete, update any systems or settings that refer to the old master, such as PE client tool configurations, Code Manager hooks, Razor brokers, and CNAME records.
Deploy updated configuration to nodes by running Puppet or waiting for the next scheduled run.
Note: If you use the direct Puppet workflow, where agents use cached catalogs, you must manually deploy the new configuration by running puppet job run --no-enforce-environment --query 'nodes {deactivated is null and expired is null}'
(Optional) Provision a new replica in order to maintain high availability.
Note: Agent configuration must be updated before provisioning a new replica. If you re-use your old master’s node name for the new replica, agents with outdated configuration might use the new replica as a master before it’s fully provisioned.

Enable a new replica using a failed master

After promoting a replica, you can use your old master as a new replica, effectively swapping the roles of your failed master and promoted replica.

Before you begin

The puppet infrastructure run command leverages built-in Bolt plans to automate certain management tasks. To use this command, you must be able to connect using SSH from your master to any nodes that the command modifies. You can establish an SSH connection using key forwarding, a local key file, or by specifying keys in .ssh/config on your master. For more information, see Bolt OpenSSH configuration options.
You must have token-based authentication configured.

On your promoted replica logged in as root, run puppet infrastructure run enable_ha_failover, specifying these parameters:

host — Hostname of the failed master. This node becomes your new replica.
caserver — Hostname of the promoted replica that's serving as your new master.
topology — Architecture used in your environment, either mono or mono-with-compile
replication_timeout_secs — Optional number of seconds allowed to complete provisioning and enabling of the new replica before the command fails.

For example:

puppet infrastructure run enable_ha_failover host=<FAILED_MASTER_HOSTNAME> caserver=<PROMOTED_REPLICA_HOSTNAME> topology=mono

Forget a replica

Forgetting a replica cleans up classification and database state, preventing degraded performance over time.

Before you begin

Ensure you have a valid admin RBAC token. See Generate a token using puppet-access.

Run the forget command whenever a replica node is destroyed, even if you plan to replace it with a replica with the same name.

Verify that the replica to be removed is permanently offline.
On the primary master, as the root user, run puppet infrastructure forget <REPLICA NODE NAME>
The replica is decommissioned, the node is purged as an agent, and a Puppet run is completed on the master.

Reinitialize a replica

If you encounter certain errors on your primary master replica after provisioning, you can reinitialize the replica. Reinitializing destroys and re-creates replica databases, as specified.

Before you begin

Your primary master must be fully functional and the replica must be able to communicate with the primary master.

CAUTION: If you reinitialize a functional replica that you already enabled, the replica is unavailable to serve as backup in a failover during reinitialization.

Reinitialization is not intended to fix slow queries or intermittent failures. Reinitialize your replica only if it’s inoperational or you see replication errors.

On the primary master replica, reinitialize databases as needed:
- All databases: puppet infrastructure reinitialize replica
- Specific databases: puppet infrastructure reinitialize replica --db <DATABASE> where <DATABASE> is pe-activity, pe-classifier, pe-orchestrator, or pe-rbac.
Follow prompts to complete the reinitialization.