Key Concepts
This page explains how instance groups, instances, backups, failover, volumes, and parameter groups are structured and operated in the PostgreSQL service. For how to create and manage each resource, see the relevant How-to Guides.
| Concept | Description |
|---|---|
| Instance group | Unit that manages instance and backup lifecycles |
| Instance | VM (Virtual Machine) unit included in an instance group. It has a Primary or Standby role depending on the availability configuration |
| Instance type | Virtualized resource specifications composed of vCPU and memory |
| Backup | Data copy created by instance group and used for restore |
| Failover | High availability feature that switches to a Standby instance when the Primary instance fails or when a manual request is made |
| Volume | Block Storage-based storage space that provides the PostgreSQL database |
| Network and security | Network and security configuration for accessing PostgreSQL instances in a VPC environment |
| Parameter group | Object that manages PostgreSQL configuration parameters by version and group |
Instance group
An instance group is an object that manages the lifecycle of instances and backups.
PostgreSQL instance groups have various status values, including operational and terminated states, which users can check and use to manage instance groups.
Instance group lifecycle and status values
When you create a PostgreSQL instance group, it starts in the Pending state and transitions through Provisioning and Primary Available to the Available state. A PostgreSQL instance group in the Available state can be accessed through the endpoint and port of the network selected by the user. The default ports for a PostgreSQL instance group are 5432(Primary) and 5433(Standby), and you can specify a desired port in the 1024-65535 range during creation.
Instance group lifecycle
PostgreSQL instance group lifecycle
| Status | Description |
|---|---|
Pending | Preparing to configure the instance group - An instance group starts in the Pending state when first created |
Provisioning | Creating instances in the instance group and configuring required packages |
Primary Available | Resources for Standby instances are being allocated and configured, while the Primary instance is available for normal use - High availability configuration itself is maintained, and the Primary instance is available - Example: Standby instance Provisioning, Standby instance failure or interruption |
Switching | Manual or automatic failover is in progress |
Available | All instances in the instance group are in the Running state, and users can use the group normally- Access through the Endpoint IP and port of the selected network - Ports can be specified in the 1024-65535 range. Default ports are 5432(Primary), 5433(Standby) |
Terminating | Terminating all instances in the instance group and deleting all resources, including backups performed in the instance group |
Terminated | All resources in the instance group have been deleted |
Error | Some instances in the instance group have errors and are temporarily unavailable |
Storage-Full | Log or Data disk usage of an instance in the PostgreSQL instance group is 85% or higher, or available capacity is 30 GB or less - If there is an instance in the Storage-Error state, requests other than volume expansion are unavailable |
Fatal | An error occurred while configuring the instance group, making transition to a normal state impossible - Example: VM creation failure |
Instance
An instance is a VM (Virtual Machine) managed by an instance group.
PostgreSQL instances are virtualized databases that include CPU and memory, and they are included in PostgreSQL instance groups. Each PostgreSQL instance has a status value, and its role is determined as Primary or Standby based on the availability configuration.
For how to view and manage instances, see Manage instances.
Instance roles
| Instance role | Description |
|---|---|
| Primary | Instance generally used by users for reads and writes - Users can access the PostgreSQL instance through the endpoint |
| Standby | Instance for high availability in case of Primary failure - Created when instance availability is selected as High availability - Also acts as a read-only replica |
Instance types
The PostgreSQL service supports selecting optimized instance types based on usage purpose and expected workload.
For each instance type in a PostgreSQL instance group, the managed database specifications and settings are determined. You can select an instance type when creating a PostgreSQL instance group, and charges are based on resource usage.
m2a (general purpose), r2a (memory optimized) types
| PostgreSQL instance type | Default vCPU | Memory (GiB) |
|---|---|---|
| m2a.large | 2 | 8 |
| m2a.xlarge | 4 | 16 |
| m2a.2xlarge | 8 | 32 |
| m2a.4xlarge | 16 | 64 |
| m2a.8xlarge | 32 | 128 |
| m2a.12xlarge | 48 | 192 |
| m2a.16xlarge | 64 | 256 |
| m2a.24xlarge | 96 | 384 |
| r2a.large | 2 | 16 |
| r2a.xlarge | 4 | 32 |
| r2a.2xlarge | 8 | 64 |
| r2a.4xlarge | 16 | 128 |
| r2a.8xlarge | 32 | 256 |
| r2a.12xlarge | 48 | 384 |
| r2a.16xlarge | 64 | 512 |
| r2a.24xlarge | 96 | 768 |
Instance lifecycle and status values
Instances start in the Pending state and transition through Starting to the Running state.
PostgreSQL instance lifecycle
| Status | Description |
|---|---|
Pending | Preparing to configure the instance. Initial state |
Starting | Creating resources for instance configuration |
Restarting | Restarting the instance, caused by the user's restart request |
Warning | Service communication for the instance is possible, but some features are restricted |
Storage-Warning | Log or Data disk usage of the instance is 85% or higher, or available capacity is 30 GB or less - After capacity is secured, the state changes after waiting 5 minutes when transitioning to Running |
Volume-Extending | Expanding the volume size of the Log or Data disk connected to the instance, caused by the user's volume expansion request |
Running | The instance is running and the PostgreSQL service is operating normally |
Terminating | Terminating and returning the instance, and deleting resources |
Terminated | The instance has been terminated and all resources have been deleted |
Error | The instance has an error and service use is difficult * Example: VM internal process issue |
Storage-Error | Log or Data disk usage of the instance is 95% or higher, or available capacity remains 10 GB or less for more than 5 minutes |
Fatal | Instance creation failed and transition to a normal state is difficult |
Availability and roles
| Availability mode | Instance count | Description |
|---|---|---|
| Single | 1 | Creates only a Primary instance |
| High Availability (HA) | Up to 6 | Creates 1 Primary and 1-5 Standby instances |
Availability status
Availability status refers to the state of data replication between PostgreSQL instances. It applies only to instance groups whose instance availability is selected as high availability.
PostgreSQL instance availability status
| Availability status | Description |
|---|---|
Configuring | Data replication settings for PostgreSQL instances are being configured |
Configured | Data replication for PostgreSQL instances is operating normally |
Unavailable | Data replication for PostgreSQL instances has stopped |
Backup
Backups are managed by PostgreSQL instance group.
For how to view and manage backups, see Manage backups.
Backup lifecycle and status values
Backups start in the Pending state, transition through Processing, and complete when they reach the Available state.
PostgreSQL backup lifecycle
| Status | Description |
|---|---|
Pending | Backup request has been submitted |
Processing | Backup is in progress |
Available | Backup is complete and available |
Restoring | Backup is being used for restore. It cannot be deleted. |
Deleting | Backup is being deleted |
Deleted | Backup has been fully deleted |
Error | Backup failed and cannot be used |
Fatal | Backup creation failed completely |
Failover
PostgreSQL supports high availability (HA). If high availability is selected for the instance group availability, multiple Standby instances can be created. If a failure makes normal service difficult, failover can be performed. The PostgreSQL service supports both automatic and manual failover.
For how to perform manual failover, see Manual instance failover.
Failover may cause temporary service interruption.
Failover status
| Status | Description |
|---|---|
SWITCHING | Failover is in progress. PostgreSQL service cannot be used. |
PRIMARY-AVAILABLE | Standby instances are being configured. |
Volume
PostgreSQL service provides databases by using volumes, which are Block Storage devices. Users do not need to create or configure Block Storage directly.
For how to expand volumes, see Expand PostgreSQL instance group volumes.
Network and security
All PostgreSQL instances are provided in a VPC environment. You can build a logically isolated service environment by using VPC network and security features. For more information, see VPC.
Parameter group
You can create and manage PostgreSQL parameter values by group.
For how to create and modify parameter groups, see Manage parameter groups. For how to change the parameter group applied to an instance group, see Change parameter group.
Parameter application status
Parameter group application status
| Status | Description |
|---|---|
Pending | Waiting for parameter application |
Applying | Applying parameters to the instance group |
In-Sync | Parameters have been applied normally to the instance group |
Partial-Sync | Parameters have been applied to only some instances in the instance group - Occurs when parameter application fails because the instance group is in Provisioning or some instances are not in a normal state |
Error-Sync | Failed to apply parameters to the instance group - You can retry parameter application, and the status changes to Applying when retried |
Suspended | Waiting for the next task because the previous instance group failed parameter application during sequential application - Waiting instance groups change from Pending to Suspended, and parameter application can be retried- When retried, the status changes to Applying |