Configuring Postgres Enterprise Manager (PEM) v23

TPA will install and configure PEM when tpaexec configure command is run with --enable-pem command line option.

The default behavior with --enable-pem is to enable pem-agent role for all postgres instances in the cluster. pem-agent role will also be added to barman nodes when --enable-pg-backup-api command line option is used alongside --enable-pem.

A dedicated instance named pemserver will also be added to the cluster.

Since PEM server uses postgres backend; pemserver instance implicitly uses postgres role as well which ensures that pemserver gets a valid postgres cluster configured for use as PEM backend. All configuration options available for a normal postgres instance are valid for PEM's backend postgres instance as well. See following for details:

Note that PEM is only available via EDB's package repositories and therefore requires a valid subscription.

Supported architectures

PEM is supported with M1 and BDR-Always-ON architectures via --enable-pem configuration command line option. You could optionally edit the generated cluster config (config.yml) and assign or remove pem-agent role from any postgres instance in the cluster in order to enable or disable PEM there.

Note that PEM server does not support pgextended for a backend yet.

PEM configuration

TPA will configure pem agents and pem server with the appropriate instance-specific settings, with remaining settings set to the respective default values. Some of the configuration options may be exposed for user configuration at some point in future.

PEM server's web interface is configured to run on https and uses 443 port for the same. PEM's webserver configuration uses self-signed certificates.

Default login credentials for PEM server web interface use the postgres backend database user which is set to postgres for postgresql and enterprisedb for EPAS clusters by default. You could get the login password for the web interface by running tpaexec show-password $clusterdir $user.

Shared PEM server

Some deployments may want to use a single PEM sever for monitoring and managing multiple clusters in the organization. Shared pem server deployment within tpaexec is supported via pem_shared variable that you could set via vars: under the pem server instance for the given cluster config that plans to use an existing pem server. pem_shared is a boolean variable so possible values are true and false(default). When declaring a pemserver instance as shared, we tell the given cluster config that pemserver instance is in fact managed by a separate cluster config that provisioned and deployed the pem server in the first place. So any changes we wanted to make to the pem server instance including postgres backend for pem would be managed by the cluster where pemserver instance is NOT declared as a shared pem instance.

A typical workflow for using a shared pem server across multiple clusters would look something like this:

Create a tpaexec cluster with a single instance that has pem-server role (call it 'pem-cluster' for this example). We could as easily use the same workflow in a scenario where pem is provisioned as part of a larger cluster and not just a single instance that runs as pemserver but we use a single node cluster because it is easier to use that as an example and arguably easy to maintain as well.
In the other cluster (pg-cluster for example), reference this particular pemserver from $clusters/pem-cluster as a shared pem server instance and use bare as platform so we are not trying to create a new pemserver instance. Also specify the IP address of the pemserver that this cluster can use to access pemserver instance.
```
- Name: pemserver
  node: 5
  role:
  - pem-server
  platform: bare
  public_ip: 13.213.53.205
  private_ip: 10.33.15.102
  vars:
    pem_shared: true
```

Before running deploy in the postgres cluster, make sure that pg-cluster can access pem server instance via ssh. You can allow this access by copying pg-cluster's public key to pem server instance via ssh-copy-id and then do an ssh to make sure you can login without having to specify the password.

# add pem-clusters key to the ssh-agent (handy for `aws` platform)
$ cd $clusters/pem-cluster
$ ssh-add id_pem-clutser
$ cd $clusters/pg-cluster
$ ssh-keyscan -4 $pem-server-ip >> known_hosts
$ ssh-copy-id -i id_pg-cluster.pub -o 'UserKnownHostsFile=tpa_known_hosts' $user@$pem-server-ip
$ ssh -F ssh_config pemserver

Update postgresql config on pem server node so it allows connections from the new pg-cluster. You can modify existing pg_hba.conf on pem server by adding new entries to pem_postgres_extra_hba_settings under vars: in pem-cluster's config.yml. For example:

instances:
- Name: pemserver
  location: main
  node: 1
  role:
  - pem-server
  vars:
    pem_postgres_extra_hba_settings:
      - "# Allow pem connections from pg-cluster1.quire"
      - hostssl pem +pem_agent 10.33.15.108/32 cert
      - "# Allow pem connections from pg-cluster1.upside"
      - hostssl pem +pem_agent 10.33.15.104/32 cert
      - "# Allow pem connections from pg-cluster2.zippy"
      - hostssl pem +pem_agent 10.33.15.110/32 cert
      - "# Allow pem connections from pg-cluster2.utopic"
      - hostssl pem +pem_agent 10.33.15.109/32 cert

and then run tpaexec provision $clusters/pem-cluster followed by tpaexec deploy $clusters/pem-cluster. When complete, nodes from your new pg-cluster should be able to speak with pem server backend.

In order to make sure pem agents from the nodes in pg-cluster can connect and register with the pem server backend, you must first export EDB_PEM_CREDENTIALS_FILE=/path/to/pem/credentials/file before you run tpaexec deploy. Credentials file is a text file that contains your access credentials to the pemserver's backend postgres instance in the username:password format.
```
$ cat pem_creds
postgres:f1I%fw!QmWevdzw#EL#$Ulu1cWhg7&RT
```
If you don't know the backend password, you can get that by using show-password tpaexec command.
```
tpaexec show-password $pem-clusterdir $user
```

Run tpaexec deploy $clusters/pg-cluster so pem is deployed on the new pg-cluster while using shared pem server instance.

Connecting to the PEM UI

PEM UI runs on https interface so you can connect with a running instance of PEM server via https://$pem-server-ip/pem. Login credentials for PEM UI are set to the postgres backend user which uses postgres or enterprisedb for postgresql and epas flavours respectively. tpaexec's show-password command will show the password for the backend user. For example:

tpaexec show-password $clusterdir $user

See PEM documentation for more details on PEM configuration and usage.

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