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Crunchy PostgreSQL Operator > Advanced Topics > Custom Configuration

Custom Configuration

Custom PostgreSQL Configuration

Users and administrators can specify a custom set of PostgreSQL configuration files to be used when creating a new PostgreSQL cluster. The configuration files you can change include -

postgres-ha.yaml
setup.sql

Different configurations for PostgreSQL might be defined for the following -

OLTP types of databases
OLAP types of databases
High Memory
Minimal Configuration for Development
Project Specific configurations
Special Security Requirements

Global ConfigMap

If you create a configMap called pgo-custom-pg-config with any of the above files within it, new clusters will use those configuration files when setting up a new database instance. You do NOT have to specify all of the configuration files. It is entirely up to your use case to determine which to use.

An example set of configuration files and a script to create the global configMap is found at

$PGOROOT/examples/custom-config

If you run the create.sh script there, it will create the configMap that will include the PostgreSQL configuration files within that directory.

Config Files Purpose

The postgres-ha.yaml file is the main configuration file that allows for the configuration of a wide variety of tuning parameters for you PostgreSQL cluster. This includes various PostgreSQL settings, e.g. those that should be applied to files such as postgresql.conf, pg_hba.conf and pg_ident.conf, as well as tuning parameters for the High Availability features included in each cluster. The various configuration settings available can be found here

The setup.sql file is a SQL file that is executed following the initialization of a new PostgreSQL cluster, specifically after initdb is run when the database is first created. Changes would be made to this if you wanted to define which database objects are created by default.

Granular Config Maps

Granular config maps can be defined if it is necessary to use a different set of configuration files for different clusters rather than having a single configuration (e.g. Global Config Map). A specific set of ConfigMaps with their own set of PostgreSQL configuration files can be created. When creating new clusters, a --custom-config flag can be passed along with the name of the ConfigMap which will be used for that specific cluster or set of clusters.

Defaults

If there is no reason to change the default PostgreSQL configuration files that ship with the Crunchy Postgres container, there is no requirement to. In this event, continue using the Operator as usual and avoid defining a global configMap.

Modifying PostgreSQL Cluster Configuration

Once a PostgreSQL cluster has been initialized, its configuration settings can be updated and modified as needed. This done by modifying the <clusterName>-pgha-config ConfigMap that is created for each individual PostgreSQL cluster.

The <clusterName>-pgha-config ConfigMap is populated following cluster initializtion, specifically using the baseline configuration settings used to bootstrap the cluster. Therefore, any customiztions applied using a custom postgres-ha.yaml file as described in the Custom PostgreSQL Configuration section above will also be included when the ConfigMap is populated.

The various configuration settings available for modifying and updating and cluster’s configuration can be found here. Please proceed with caution when modiying configuration, especially those settings applied by default by Operator. Certain settings are required for normal operation of the Operator and the PostgreSQL clusters it creates, and altering these settings could result in expected behavior.

Types of Configuration

Within the <clusterName>-pgha-config ConfigMap are two forms of configuration:

Distributed Configuration Store (DCS): Cluster-wide configuration settings that are applied to all database servers in the PostgreSQL cluster
Local Database: Configuration settings that are applied individually to each database server (i.e. the primary and each replica) within the cluster.

The DCS configuration settings are stored within the <clusterName>-pgha-config ConfigMap in a configuration named <clusterName>-dcs-config, while the local database configurations are stored in one or more configurations named <serverName>-local-config (with one local configuration for the primary and each replica within the cluster). Please note that as described here, certain settings can only be applied via the DCS to ensure they are uniform among the primary and all replicas within the cluster.

The following is an example of the both the DCS and primary configuration settings as stored in the <clusterName>-pgha-config ConfigMap for a cluster named mycluster. Please note the mycluster-dcs-config configuration defining the DCS configuration for mycluster, along with the mycluster-local-config configuration defining the local configuration for the database server named mycluster, which is the current primary within the PostgreSQL cluster.

$ kubectl describe cm mycluster-pgha-config   
Name:         mycluster-pgha-config
Namespace:    pgouser1
Labels:       pg-cluster=mycluster
              pgha-config=true
              vendor=crunchydata
Annotations:  <none>

Data
====
mycluster-dcs-config:
----
postgresql:
  parameters:
    archive_command: source /opt/cpm/bin/pgbackrest/pgbackrest-set-env.sh && pgbackrest
      archive-push "%p"
    archive_mode: true
    archive_timeout: 60
    log_directory: pg_log
    log_min_duration_statement: 60000
    log_statement: none
    max_wal_senders: 6
    shared_buffers: 128MB
    shared_preload_libraries: pgaudit.so,pg_stat_statements.so
    temp_buffers: 8MB
    unix_socket_directories: /tmp,/crunchyadm
    wal_level: logical
    work_mem: 4MB
  recovery_conf:
    restore_command: source /opt/cpm/bin/pgbackrest/pgbackrest-set-env.sh && pgbackrest
      archive-get %f "%p"
  use_pg_rewind: true

mycluster-local-config:
----
postgresql:
  callbacks:
    on_role_change: /opt/cpm/bin/callbacks/pgha-on-role-change.sh
  create_replica_methods:
  - pgbackrest
  - basebackup
  pg_hba:
  - local all postgres peer
  - local all crunchyadm peer
  - host replication primaryuser 0.0.0.0/0 md5
  - host all primaryuser 0.0.0.0/0 reject
  - host all all 0.0.0.0/0 md5
  pgbackrest:
    command: /opt/cpm/bin/pgbackrest/pgbackrest-create-replica.sh
    keep_data: true
    no_params: true
  pgbackrest_standby:
    command: /opt/cpm/bin/pgbackrest/pgbackrest-create-replica.sh
    keep_data: true
    no_master: 1
    no_params: true
  pgpass: /tmp/.pgpass
  remove_data_directory_on_rewind_failure: true
  use_unix_socket: true

Updating Configuration Settings

In order to update a cluster’s configuration settings and then apply those settings (e.g. to the DCS and/or any individual database servers), the DCS and local configuration settings within the <clusterName>-pgha-config ConfigMap can be modified. This can be done using the various commands available using the kubectl client (or the oc client if using OpenShift) for modifying Kubernetes resources. For instance, the following command can be utilized to open the ConfigMap in a local text editor, and then update the various cluster configurations as needed:

kubectl edit configmap mycluster-pgha-config

Once the <clusterName>-pgha-config ConfigMap has been updated, any changes made will be detected by the Operator, and then applied to the DCS and/or any individual database servers within the cluster.

PostgreSQL Configuration

In order to update the postgresql.conf file for a one of more database servers, the parameters section of either the DCS and/or a local database configuration can be updated, e.g.:

----
postgresql:
  parameters:
    max_wal_senders: 10

The various key/value pairs provided within the parameters section result in the configuration of the same settings within the postgresql.conf file. Please note that settings applied locally to a database server take precedence over those set via the DCS (with the exception being those that must be set via the DCS, as described here).

Also, please note that pg_hba and pg_ident sections exist to update both the pg_hba.conf and pg_ident.conf PostgreSQL configuration files as needed.

A Note on Customizing `authentication`

One of the blocks that can be modified in a local database setting is the authentication block. This can be useful for setting customizations such as TLS connection requirements (sslmode). However, one should take care when modifying this block, as modifying certain parameters can interfere with the management features that the PostgreSQL Operator provides.

In particular, one should not customize the username or password attributes within this section as that will interface with the PostgreSQL Operator. Additionally, is using the built-in support for certificate-based authentication for replication users, you should not modify the sslcert, sslkey, sslrootcert, and sslcrl entries in the replication block of the authentication block.

Restarting Database Servers

Changes to certain settings may require one or more PostgreSQL databases within the cluster to be restarted. This can be accomplished using the pgo restart command included with the pgo client. To detect if a restart is needed for a instance within a cluster called mycluster after making a configuration change, the query flag can be utilized with the pgo restart command as follows:

$ pgo restart mycluster2 --query

Cluster: mycluster2
INSTANCE                ROLE            STATUS          NODE            REPLICATION LAG         PENDING RESTART
mycluster               primary         running         node01                     0 MB                   false
mycluster-ambq          replica         running         node01                     0 MB                    true

Here we can see that the mycluster-ambq instance (i.e. the sole replica in cluster mycluster) is pending a restart, as shown by the PENDING RESTART column. A restart can then be requested as follows:

$ pgo restart mycluster --target mycluster-ambq
WARNING: Are you sure? (yes/no): yes
Successfully restarted instance mycluster

It is also possible to target multiple instances at the same time:

$ pgo restart mycluster --target mycluster --target mycluster-ambq
WARNING: Are you sure? (yes/no): yes
Successfully restarted instance mycluster
Successfully restarted instance mycluster-ambq

Or if no target is specified, the all instances within the cluster will be restarted:

$ pgo restart mycluster
WARNING: Are you sure? (yes/no): yes
Successfully restarted instance mycluster
Successfully restarted instance mycluster-ambq

Refreshing Configuration Settings

If necessary, it is possible to refresh the configuration stored within the <clusterName>-pgha-config ConfigMap with a fresh copy of either the DCS configuration and/or the configuration for one or more local database servers. This is specifically done by fully deleting a configuration from the <clusterName>-pgha-config ConfigMap. Once a configuration has been deleted, the Operator will detect this and refresh the ConfigMap with a fresh copy of that specific configuration.

For instance, the following kubectl patch command can be utilized to remove the mycluster-dcs-config configuration from the example above, causing that specific configuration to be refreshed with a fresh copy of the DCS configuration settings for mycluster:

kubectl patch configmap mycluster-pgha-config \
  --type='json' -p='[{"op": "remove", "path": "/data/mycluster-dcs-config"}]'

Custom pgBackRest Configuration

Users can configure pgBackRest by passing the name of an existing ConfigMap to the --pgbackrest-custom-config flag when creating a PostgreSQL cluster. The entire contents of that ConfigMap appear as files in pgBackRest’s config-include-path directory.

Regardless of the flags passed at creation, every PostgreSQL cluster is automatically configured to read from a ConfigMap named <clusterName>-config-backrest and a Secret named <clusterName>-config-backrest. These objects can be populated either before or after a PostgreSQL cluster is created. The entire contents of each appear as files in pgBackRest’s config-include-path directory.

Though the above is very flexible, not all pgBackRest settings can be managed this way. There are a few that are always overridden by the PostgreSQL Operator (the path to the PostgreSQL data directory, for example).