当 AWS::CustomResource 具有列表类型输出时如何获取选择性项目

Question

我正在尝试在 Cloudformation 模板中创建 AWS 自定义资源以检索 MSK 代理 DNS 详细信息。

下面是我的示例 lambda 代码：

import json
import logging
import boto3
import subprocess
import shlex
import os
import time
from hashlib import md5
from crhelper import CfnResource
from time import sleep

logger = logging.getLogger(__name__)
helper = CfnResource(json_logging=True, log_level='DEBUG')




@helper.create
@helper.update
def create_handler(event, _):
    print('Received event: %s' % json.dumps(event))
    retry_timeout = 0
    if "Timeout" in event['ResourceProperties']:
        retry_timeout = int(event['ResourceProperties']["Timeout"])
    if retry_timeout > 600:
        retry_timeout = 600
    MskArn = event['ResourceProperties']['MskArn']
    kafkaClient = boto3.client('kafka', region_name=event['ResourceProperties']['aws-region'])
    while True:
        try:
            response = kafkaClient.list_nodes(
                ClusterArn=event['ResourceProperties']['MskArn']
            )
            r1=response['NodeInfoList']
            BrokerCount=len(r1)
            i = 0
            DNS=[]
            name = event['ResourceProperties']['Name']
            while i < BrokerCount:
                broker=response['NodeInfoList'][i]
                brokerDNS=broker['BrokerNodeInfo']['Endpoints'][0]
                DNS.append(brokerDNS)
                print(brokerDNS)
                i = i + 1
            return DNS
            outp = DNS
            break
        except Exception as e:
            if retry_timeout < 1:
                raise
            else:
                logging.error('Exception: %s' % e, exc_info=True)
                print("retrying until timeout...")
                time.sleep(5)
                retry_timeout = retry_timeout - 5
    response_data = {}
    if "ResponseKey" in event['ResourceProperties']:
        response_data[event['ResourceProperties']["ResponseKey"]] = outp
    if len(outp.encode('utf-8')) > 1000:
        outp = 'MD5-' + str(md5(outp.encode('utf-8')).hexdigest())
    helper.Data.update(response_data)
    return outp


def lambda_handler(event, context):
    helper(event, context)
    print(response_data)

以下是我的示例 AWS Cloudformation 模板：

---
AWSTemplateFormatVersion: '2010-09-09'
Description: 'To Get MSK Broker DNS CloudFormation Template'
Resources:
  GetMskBrokersDetails:
    Type: "Custom::GetMskDetails"
    Version: '1.0'
    Properties:
      Name: GetMskBrokerDNS
      ServiceToken: LAMBDA_ARN
      aws-region: !Sub "${AWS::Region}"
      MskArn: MSK_CLUSTER_ARN

Outputs:
  MskBrokerDns1:
    Description: Msk Broker DNS Records
    Value: !Ref GetMskBrokersDetails

以上工作正常。当我执行上述模板时，它会给出以下输出。

MskBrokerDns1   ['b-1.kafka.ap-south-1.amazonaws.com', 'b-2.kafka.ap-south-1.amazonaws.com']

由于上面的输出是列表，我们希望在两个单独的输出变量中获得上面的 DNS 详细信息。如下：

Outputs:
  MskBrokerDns1:
    Description: Msk Broker DNS Records
    Value: !Select [ 0, !Ref GetMskBrokersDetails ]
  MskBrokerDns2:
    Description: Msk Broker DNS Records
    Value: !Select [ 1, !Ref GetMskBrokersDetails ]

当我们尝试执行具有上述更改的模板时，我们得到以下错误：

模板错误：Fn::Select 需要一个包含两个元素的列表参数：一个整数索引和一个列表

所以我们请求社区支持，我们如何解决上述问题。

Answer 1

经过一些尝试和尝试，我们能够得到我们想要的响应。这可能不是有效的方法。 Lambda 代码：

import json
import logging
import boto3
import subprocess
import shlex
import os
import time
from hashlib import md5
from crhelper import CfnResource
from time import sleep

logger = logging.getLogger(__name__)
helper = CfnResource(json_logging=True, log_level='DEBUG')




@helper.create
@helper.update
def create_handler(event, _):
    print('Received event: %s' % json.dumps(event))
    retry_timeout = 0
    if "Timeout" in event['ResourceProperties']:
        retry_timeout = int(event['ResourceProperties']["Timeout"])
    if retry_timeout > 600:
        retry_timeout = 600
    MskArn = event['ResourceProperties']['MskArn']
    kafkaClient = boto3.client('kafka', region_name=event['ResourceProperties']['aws-region'])
    while True:
        try:
            response = kafkaClient.list_nodes(
                ClusterArn=event['ResourceProperties']['MskArn']
            )
            r1=response['NodeInfoList']
            BrokerCount=len(r1)
            i = 0
            DNS=[]
            name = event['ResourceProperties']['Name']
            while i < BrokerCount:
                broker=response['NodeInfoList'][i]
                brokerDNS=broker['BrokerNodeInfo']['Endpoints'][0]
                DNS.append(brokerDNS)
                i = i + 1
            outp = DNS
            break
        except Exception as e:
            if retry_timeout < 1:
                raise
            else:
                logging.error('Exception: %s' % e, exc_info=True)
                print("retrying until timeout...")
                time.sleep(5)
                retry_timeout = retry_timeout - 5
    response_data = {}
    response_data['BrokerDNS1'] = DNS[0]
    response_data['BrokerDNS2'] = DNS[1]
    print(response_data)
    helper.Data.update(response_data)

def lambda_handler(event, context):
    helper(event, context)

以下是 AWS Cloudformation 资源定义：

  GetMskBrokersDetails:
    Type: "Custom::GetMskDetails"
    Version: '1.0'
    Properties:
      Name: GetMskBrokerDNS
      ServiceToken: !Ref MskGetBrokerDnsLambdaArn
      aws-region: !Sub "${AWS::Region}"
      MskArn: !Ref MskCluster
Outputs:
  MskBrokerDns1:
    Description: Msk Broker DNS Records
    Value: !GetAtt GetMskBrokersDetails.BrokerDNS1
  MskBrokerDns2:
    Description: Msk Broker DNS Records
    Value: !GetAtt GetMskBrokersDetails.BrokerDNS2