Request to add graph for InnoDB History List Length to CloudWatch Metrics for RDS MySQL Databases

The InnoDB History List Length is an important metric to monitor to ensure that Disk I/O is sufficient for an instance. See Baron Schwartz excellent article about what it is.

When the InnoDB purge process is not able to keep up, it can lead to very unexpected behavior, such as otherwise unexplainable high disk I/O, and slow performance. example

It would be useful for the community to have this metric monitored automatically with CloudWatch for all MySQL instances. You can obtain the value easily with the command

SELECT count
FROM information_schema.innodb_metrics
WHERE name = 'trx_rseg_history_len'

Since InnoDB is the default storage engine on MySQL and Aurora/MySQL instances, this would help customer understand if their write capacity is insufficient, and provide a starting point for investigating more complex issues.