aurora_global_db_status - Amazon Aurora
SyntaxArgumentsReturn typeUsage notesExamples

aurora_global_db_status

Displays information about various aspects of Aurora global database lag, specifically, lag of the underlying Aurora storage (so called durability lag) and lag between the recovery point objective (RPO).

Syntax

aurora_global_db_status()

Arguments

None.

Return type

SETOF record with the following columns:

  • aws_region – The AWS Region that this DB cluster is in. For a complete listing of AWS Regions by engine, see Regions and Availability Zones.

  • highest_lsn_written – The highest log sequence number (LSN) that currently exists on this DB cluster. A log sequence number (LSN) is a unique sequential number that identifies a record in the database transaction log. LSNs are ordered such that a larger LSN represents a later transaction.

  • durability_lag_in_msec – The difference in the timestamp values between the highest_lsn_written on a secondary DB cluster and the highest_lsn_written on the primary DB cluster. A value of -1 identifies the primary DB cluster of the Aurora global database.

  • rpo_lag_in_msec – The recovery point objective (RPO) lag. The RPO lag is the time it takes for the most recent user transaction COMMIT to be stored on a secondary DB cluster after it's been stored on the primary DB cluster of the Aurora global database. A value of -1 denotes the primary DB cluster (and thus, lag isn't relevant).

    In simple terms, this metric calculates the recovery point objective for each Aurora PostgreSQL DB cluster in the Aurora global database, that is, how much data might be lost if there were an outage. As with lag, RPO is measured in time.

  • last_lag_calculation_time – The timestamp that specifies when values were last calculated for durability_lag_in_msec and rpo_lag_in_msec. A time value such as 1970-01-01 00:00:00+00 means this is the primary DB cluster.

  • feedback_epoch – The epoch that the secondary DB cluster uses when it generates hot standby information. A hot standby is a DB instance that supports connections and queries while the primary DB is in recovery or standby mode. The hot standby information includes the epoch (point in time) and other details about the DB instance that's being used as a hot standby. For more information, see Hot Standby in the PostgreSQL documentation.

  • feedback_xmin – The minimum (oldest) active transaction ID used by a secondary DB cluster.

Usage notes

This function shows replication statistics for an Aurora global database. It shows one row for each DB cluster in an Aurora PostgreSQL global database. You can run this function from any instance in your Aurora PostgreSQL global database.

To evaluate Aurora global database replication lag, which is the visible data lag, see aurora_global_db_instance_status.

To learn more about using aurora_global_db_status and aurora_global_db_instance_status to monitor Aurora global database lag, see Monitoring Aurora PostgreSQL-based global databases. For more information about Aurora global databases, see Overview of Amazon Aurora Global Database.

Examples

This example shows how to display cross-region storage statistics.

=> SELECT CASE 
          WHEN '-1' = durability_lag_in_msec THEN 'Primary'
          ELSE 'Secondary'
       END AS global_role,
       *
  FROM aurora_global_db_status();
 global_role | aws_region | highest_lsn_written | durability_lag_in_msec | rpo_lag_in_msec | last_lag_calculation_time  | feedback_epoch | feedback_xmin
-------------+------------+---------------------+------------------------+-----------------+----------------------------+----------------+---------------
 Primary     | eu-west-1  |           131031557 |                     -1 |              -1 | 1970-01-01 00:00:00+00     |              0 |             0
 Secondary   | eu-west-2  |           131031554 |                    410 |               0 | 2021-06-01 18:59:36.124+00 |              0 |         12640
 Secondary   | eu-west-3  |           131031554 |                    410 |               0 | 2021-06-01 18:59:36.124+00 |              0 |         12640