# 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                                                                                                                          | Type       | Value   |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------------------ | ---------- | ------- |
| `replicas`         | Number of Postgres replicas.                                                                                                         | `int`      | `2`     |
| `resources`        | Explicit CPU and memory configuration for each PostgreSQL replica. When omitted, the preset defined in `resourcesPreset` is applied. | `object`   | `{}`    |
| `resources.cpu`    | CPU available to each replica.                                                                                                       | `quantity` | `""`    |
| `resources.memory` | Memory (RAM) available to each replica.                                                                                              | `quantity` | `""`    |
| `resourcesPreset`  | Default sizing preset used when `resources` is omitted.                                                                              | `string`   | `micro` |
| `size`             | Persistent Volume Claim size available for application data.                                                                         | `quantity` | `10Gi`  |
| `storageClass`     | StorageClass used to store the data.                                                                                                 | `string`   | `""`    |
| `external`         | Enable external access from outside the cluster.                                                                                     | `bool`     | `false` |


### Application-specific parameters

| Name                                    | Description                                                      | Type     | Value |
| --------------------------------------- | ---------------------------------------------------------------- | -------- | ----- |
| `postgresql`                            | PostgreSQL server configuration.                                 | `object` | `{}`  |
| `postgresql.parameters`                 | PostgreSQL server parameters.                                    | `object` | `{}`  |
| `postgresql.parameters.max_connections` | Maximum number of concurrent connections to the database server. | `int`    | `100` |


### Quorum-based synchronous replication

| Name                     | Description                                                                        | Type     | Value |
| ------------------------ | ---------------------------------------------------------------------------------- | -------- | ----- |
| `quorum`                 | Quorum configuration for synchronous replication.                                  | `object` | `{}`  |
| `quorum.minSyncReplicas` | Minimum number of synchronous replicas required for commit.                        | `int`    | `0`   |
| `quorum.maxSyncReplicas` | Maximum number of synchronous replicas allowed (must be less than total replicas). | `int`    | `0`   |


### Users configuration

| Name                      | Description                                  | Type                | Value   |
| ------------------------- | -------------------------------------------- | ------------------- | ------- |
| `users`                   | Users configuration map.                     | `map[string]object` | `{}`    |
| `users[name].password`    | Password for the user.                       | `string`            | `""`    |
| `users[name].replication` | Whether the user has replication privileges. | `bool`              | `false` |


### Databases configuration

| Name                             | Description                              | Type                | Value |
| -------------------------------- | ---------------------------------------- | ------------------- | ----- |
| `databases`                      | Databases configuration map.             | `map[string]object` | `{}`  |
| `databases[name].roles`          | Roles assigned to users.                 | `object`            | `{}`  |
| `databases[name].roles.admin`    | List of users with admin privileges.     | `[]string`          | `[]`  |
| `databases[name].roles.readonly` | List of users with read-only privileges. | `[]string`          | `[]`  |
| `databases[name].extensions`     | List of enabled PostgreSQL extensions.   | `[]string`          | `[]`  |


### Backup parameters

| Name                     | Description                                            | Type     | Value                               |
| ------------------------ | ------------------------------------------------------ | -------- | ----------------------------------- |
| `backup`                 | Backup configuration.                                  | `object` | `{}`                                |
| `backup.enabled`         | Enable regular backups.                                | `bool`   | `false`                             |
| `backup.schedule`        | Cron schedule for automated backups.                   | `string` | `0 2 * * * *`                       |
| `backup.retentionPolicy` | Retention policy (e.g. "30d").                         | `string` | `30d`                               |
| `backup.destinationPath` | Destination path for backups (e.g. s3://bucket/path/). | `string` | `s3://bucket/path/to/folder/`       |
| `backup.endpointURL`     | S3 endpoint URL for uploads.                           | `string` | `http://minio-gateway-service:9000` |
| `backup.s3AccessKey`     | Access key for S3 authentication.                      | `string` | `<your-access-key>`                 |
| `backup.s3SecretKey`     | Secret key for S3 authentication.                      | `string` | `<your-secret-key>`                 |


### Bootstrap (recovery) parameters

| Name                     | Description                                                         | Type     | Value   |
| ------------------------ | ------------------------------------------------------------------- | -------- | ------- |
| `bootstrap`              | Bootstrap configuration.                                            | `object` | `{}`    |
| `bootstrap.enabled`      | Whether to restore from a backup.                                   | `bool`   | `false` |
| `bootstrap.recoveryTime` | Timestamp (RFC3339) for point-in-time recovery; empty means latest. | `string` | `""`    |
| `bootstrap.oldName`      | Previous cluster name before deletion.                              | `string` | `""`    |


## 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        
```