aws-cdk-lib/aws-rds/DatabaseInstance: Get log group of cloudwatchLogsExports

[Korbi10]

Describe the feature

As software developer I would like to get the new created log group of an DatabaseInstance if the DatabaseInstance has the cloudwatchLogsExport property set, so that I can build metric filter based on that log group and I do not have to calculate the naming behavior like AWS does

Use Case

Currently in our database stack we get the log group of the DatabaseInstance by calculating the name by ourself which looks for the Metric filter Like this:

new MetricFilter(this, 'SomeID', {
logGroup: LogGroup.fromLogGroupName(this, 'SomeID', /aws/rds/instance/${this.databaseInstance.instanceIdentifier}/postgresql),
filterPattern: FilterPattern.anyTerm('ERROR', 'Caused by', 'error'),
metricName: logMetrics.metricName,
metricNamespace: logMetrics.namespace,
defaultValue: 0,
metricValue: '1',
});

this indicates, that we always knew the DatabaseInstance identifier and the used engine. Also we rely here on the naming convention of AWS. This seems dangerous to me.

Proposed Solution

The DatabaseInstance has a method or Property which contains the log group name or ARN so that we can get it in other services.

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.23.0

Environment details (OS name and version, etc.)

Windows 10, Typescript

[peterwoodworth]

Currently you could access these log groups through escape hatches, by selecting the proper child from the DatabaseInstance.node.findChild(). I would suggest looking at the synthesized construct tree (cdk.out/tree.json) to know which log groups you want to access

We create the log groups here

aws-cdk/packages/@aws-cdk/aws-rds/lib/instance.ts

Lines 765 to 775 in 83f1668

	protected setLogRetention() {
	if (this.cloudwatchLogsExports && this.cloudwatchLogsRetention) {
	for (const log of this.cloudwatchLogsExports) {
	new logs.LogRetention(this, `LogRetention${log}`, {
	logGroupName: `/aws/rds/instance/${this.instanceIdentifier}/${log}`,
	retention: this.cloudwatchLogsRetention,
	role: this.cloudwatchLogsRetentionRole,
	});
	}
	}
	}

I don't see why we couldn't expose these directly from the DatabaseInstance. Leaving this up as a good first issue for anyone to submit a PR for 🙂

[GavinZZ]

I noticed that the previous PR was closed due to inactivity. Going to give it another attempt to address this issue.
Also noticed that the same issue is happening on RDS Cluster, adding log group access to cluster instance as well.

[GavinZZ]

This is now supported (pending release), detail usage can be found in README