AWS RDSのインスタンス追加時にクラスターのタグを引継ぐ

TODO

• コンソール上、急ぎリーダーを追加すると、タグ登録漏れに気付かない。
• 別途タグ未登録監視をしているが、できれば監視を減らしたい。

対策

• LambdaでRDSのCreateイベントを拾い、タグ登録する

Lambda

lambda_handler Python3.9

import json
import boto3
from botocore import response

def lambda_handler(event, context):
    tagkey = "project" #必須タグ
    dBClusterIdentifier = event["detail"]["responseElements"]["dBClusterIdentifier"]
    dBInstanceArn = event["detail"]["responseElements"]["dBInstanceArn"]

    client = boto3.client('rds')
    response = client.describe_db_clusters(
        DBClusterIdentifier = dBClusterIdentifier
    )
    
    dBClusterArn = response['DBClusters'][0]['DBClusterArn']
    clst_tags = client.list_tags_for_resource(ResourceName = dBClusterArn)
    clst_tag_list = clst_tags['TagList']

    clst_tag = next(iter(filter(lambda tag: tag['Key'] == tagkey, clst_tag_list)), None)
    tagvalue = clst_tag['Value']

    instance_tags = client.list_tags_for_resource(ResourceName = dBInstanceArn)
    tag_list = instance_tags['TagList']
    tag = next(iter(filter(lambda tag: tag['Key'] == tagkey and (tag['Value'] is not None and tag['Value'] != ''), tag_list)), None)
    
    # すでに登録済みはスルー
    if tag is not None:
        print('The tag is already registered.')
        return

    response = client.add_tags_to_resource(
        ResourceName = dBInstanceArn,
        Tags=[{
            'Key': tagkey,
            'Value': tagvalue
        }]
    )
    print(response)

    return {
        'statusCode': 200,
        'body': json.dumps('done')
    }

EventBridge (CloudWatch Events)

name: rds-create-instance
Service principal: events.amazonaws.com
url: events/home#/rules/rds-create-instance
イベントバス: default
イベントパターン:
{
  "source": [
    "aws.rds"
  ],
  "detail-type": [
    "AWS API Call via CloudTrail"
  ],
  "detail": {
    "eventSource": [
      "rds.amazonaws.com"
    ],
    "eventName": [
      "CreateDBInstance",
      "CreateDBInstanceReadReplica"
    ]
  }
}

参考

• https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/rds.html#RDS.Client.describe_db_clusters