# Managed PostgreSQL Service

PostgreSQL is currently the leading choice among relational databases, known for its robust features and performance.
The Managed PostgreSQL Service takes advantage of platform-side implementation to provide a self-healing replicated cluster.
This cluster is efficiently managed using the highly acclaimed CloudNativePG operator, which has gained popularity within the community.

## Deployment Details

This managed service is controlled by the CloudNativePG operator, ensuring efficient management and seamless operation.

- Docs: <https://cloudnative-pg.io/docs/>
- Github: <https://github.com/cloudnative-pg/cloudnative-pg>

## Operations

### How to enable backups

To back up a PostgreSQL application, an external S3-compatible storage is required.

To start regular backups, update the application, setting `backup.enabled` to `true`, and fill in the path and credentials to an  `backup.*`:

```yaml
## @param backup.enabled Enable regular backups
## @param backup.schedule Cron schedule for automated backups
## @param backup.retentionPolicy Retention policy
## @param backup.destinationPath Path to store the backup (i.e. s3://bucket/path/to/folder)
## @param backup.endpointURL S3 Endpoint used to upload data to the cloud
## @param backup.s3AccessKey Access key for S3, used for authentication
## @param backup.s3SecretKey Secret key for S3, used for authentication
backup:
  enabled: false
  retentionPolicy: 30d
  destinationPath: s3://bucket/path/to/folder/
  endpointURL: http://minio-gateway-service:9000
  schedule: "0 2 * * * *"
  s3AccessKey: oobaiRus9pah8PhohL1ThaeTa4UVa7gu
  s3SecretKey: ju3eum4dekeich9ahM1te8waeGai0oog
```

### How to recover a backup

CloudNativePG supports point-in-time-recovery.
Recovering a backup is done by creating a new database instance and restoring the data in it.

Create a new PostgreSQL application with a different name, but identical configuration.
Set `bootstrap.enabled` to `true` and fill in the name of the database instance to recover from and the recovery time:

```yaml
## @param bootstrap.enabled Restore database cluster from a backup
## @param bootstrap.recoveryTime Timestamp (PITR) up to which recovery will proceed, expressed in RFC 3339 format. If left empty, will restore latest
## @param bootstrap.oldName Name of database cluster before deleting
##
bootstrap:
  enabled: false
  recoveryTime: ""  # leave empty for latest or exact timestamp; example: 2020-11-26 15:22:00.00000+00
  oldName: "<previous-postgres-instance>"
```

### How to switch primary/secondary replica

See:

- <https://cloudnative-pg.io/documentation/1.15/rolling_update/#manual-updates-supervised>

## Parameters

### Common parameters

| Name              | Description                                                                                                                             | Value   |
| ----------------- | --------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `replicas`        | Number of Postgres replicas                                                                                                             | `2`     |
| `resources`       | Explicit CPU and memory configuration for each PostgreSQL replica. When left empty, the preset defined in `resourcesPreset` is applied. | `{}`    |
| `resourcesPreset` | Default sizing preset used when `resources` is omitted. Allowed values: nano, micro, small, medium, large, xlarge, 2xlarge.             | `micro` |
| `size`            | Persistent Volume size                                                                                                                  | `10Gi`  |
| `storageClass`    | StorageClass used to store the data                                                                                                     | `""`    |
| `external`        | Enable external access from outside the cluster                                                                                         | `false` |

### Application-specific parameters

| Name                                    | Description                                                                                                              | Value |
| --------------------------------------- | ------------------------------------------------------------------------------------------------------------------------ | ----- |
| `postgresql.parameters.max_connections` | Determines the maximum number of concurrent connections to the database server. The default is typically 100 connections | `100` |
| `quorum.minSyncReplicas`                | Minimum number of synchronous replicas that must acknowledge a transaction before it is considered committed.            | `0`   |
| `quorum.maxSyncReplicas`                | Maximum number of synchronous replicas that can acknowledge a transaction (must be lower than the number of instances).  | `0`   |
| `users`                                 | Users configuration                                                                                                      | `{}`  |
| `databases`                             | Databases configuration                                                                                                  | `{}`  |

### Backup parameters

| Name                     | Description                                                | Value                               |
| ------------------------ | ---------------------------------------------------------- | ----------------------------------- |
| `backup.enabled`         | Enable regular backups                                     | `false`                             |
| `backup.schedule`        | Cron schedule for automated backups                        | `0 2 * * * *`                       |
| `backup.retentionPolicy` | Retention policy                                           | `30d`                               |
| `backup.destinationPath` | Path to store the backup (i.e. s3://bucket/path/to/folder) | `s3://bucket/path/to/folder/`       |
| `backup.endpointURL`     | S3 Endpoint used to upload data to the cloud               | `http://minio-gateway-service:9000` |
| `backup.s3AccessKey`     | Access key for S3, used for authentication                 | `oobaiRus9pah8PhohL1ThaeTa4UVa7gu`  |
| `backup.s3SecretKey`     | Secret key for S3, used for authentication                 | `ju3eum4dekeich9ahM1te8waeGai0oog`  |

### Bootstrap (recovery) parameters

| Name                     | Description                                                                                                          | Value   |
| ------------------------ | -------------------------------------------------------------------------------------------------------------------- | ------- |
| `bootstrap.enabled`      | Restore database cluster from a backup                                                                               | `false` |
| `bootstrap.recoveryTime` | Timestamp (PITR) up to which recovery will proceed, expressed in RFC 3339 format. If left empty, will restore latest | `""`    |
| `bootstrap.oldName`      | Name of database cluster before deleting                                                                             | `""`    |

## Parameter examples and reference

### resources and resourcesPreset

`resources` sets explicit CPU and memory configurations for each replica.
When left empty, the preset defined in `resourcesPreset` is applied.

```yaml
resources:
  cpu: 4000m
  memory: 4Gi
```

`resourcesPreset` sets named CPU and memory configurations for each replica.
This setting is ignored if the corresponding `resources` value is set.

| Preset name | CPU    | memory  |
|-------------|--------|---------|
| `nano`      | `250m` | `128Mi` |
| `micro`     | `500m` | `256Mi` |
| `small`     | `1`    | `512Mi` |
| `medium`    | `1`    | `1Gi`   |
| `large`     | `2`    | `2Gi`   |
| `xlarge`    | `4`    | `4Gi`   |
| `2xlarge`   | `8`    | `8Gi`   |

### users

```yaml
users:
  user1:
    password: strongpassword
  user2:
    password: hackme
  airflow:
    password: qwerty123
  debezium:
    replication: true
```

### databases

```yaml
databases:          
  myapp:            
    roles:          
      admin:        
      - user1       
      - debezium    
      readonly:     
      - user2       
  airflow:          
    roles:          
      admin:        
      - airflow     
    extensions:     
    - hstore        
```