AWSLambda：如何在python中处理SNS事件

Question

如何从SNS事件中获取bucket名称？

S3存储桶将事件发布到SNS主题。此主题触发Lambda。我需要SNS，因为其他进程也会监听此事件。所以我不能直接从S3触发Lambda

在lambda函数中，我得到两个参数：event和context 我需要从事件中删除bucket名称。我本想做这样的事情：

bucket = event['Records'][0]['s3']['bucket']['name']

但这不起作用，因为根据Cloudwatch，事件参数如下所示：

{
    "Records":[
        {
            "EventSource":"aws:sns",
            "EventVersion":"1.0",
            "EventSubscriptionArn":"arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5",
            "Sns":{
                "Type":"Notification",
                "MessageId":"2330809c-29c4-5826-910d-d64a7ab22247",
                "TopicArn":"arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1",
                "Subject":"None",
                "Message":"{\\'Records\\': [{\\'EventSource\\': \\'aws:sns\\', \\'EventVersion\\': \\'1.0\\', \\'EventSubscriptionArn\\': \\'arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5\\', \\'Sns\\': {\\'Type\\': \\'Notification\\', \\'MessageId\\': \\'b611d3b2-a0d4-55fe-af0f-85648ffc2a59\\', \\'TopicArn\\': \\'arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1\\', \\'Subject\\': \\'None\\', \\'Message\\': \\'{\\n   \"Records\":[\\n      {\\n         \"EventSource\":\"aws:sns\",\\n         \"EventVersion\":\"1.0\",\\n         \"EventSubscriptionArn\":\"arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5\",\\n         \"Sns\":{\\n            \"Type\":\"Notification\",\\n            \"MessageId\":\"906fd69c-ee31-50f2-8b9d-804910f6fdcd\",\\n            \"TopicArn\":\"arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1\",\\n            \"Subject\":\"Amazon S3 Notification\",\\n            \"Message\":\"{\\\\\"Service\\\\\":\\\\\"Amazon S3\\\\\",\\\\\"Event\\\\\":\\\\\"s3:TestEvent\\\\\",\\\\\"Time\\\\\":\\\\\"2020-03-01T18:18:46.898Z\\\\\",\\\\\"Bucket\\\\\":\\\\\"s3-dam-poc-dev-inbox\\\\\",\\\\\"RequestId\\\\\":\\\\\"9534F72BD9216CA8\\\\\",\\\\\"HostId\\\\\":\\\\\"hSPdeBzns8wjrMHqkFJgw1UPMv0aZ/VOsAxw/z9wtboR+TOy8sKSKElDYxm9kszokgPsBU9T1nU=\\\\\"}\",\\n            \"Timestamp\":\"2020-03-01T18:18:47.036Z\",\\n            \"SignatureVersion\":\"1\",\\n            \"Signature\":\"FuoBKJczUXuKJ58d5SdddqnOjMwjxzG2aN+sef/0M5MFsAjRMyCNknvaXVVRrhujK39HouoOoDqyJNFzDWYR3WTYAM0Sqws9wJK9zBV9mxmMYdIurfDmVj4xsF4xuSeaMy4y/VfU2r75DxqhE3MPmA02IuGInGJsmw9CTk+Ao+kdnk/6rJT+Bt3EKK7uKj3kIWYehPDCYKYdzCsDcaP+Aaj2qEhEbkZxdaopB+pHRkMsLhZS/vHcc0Vd1eyZkRYHkxrG4FeKXVZdJT5OGuyixOSWq9YdCBJhWRnq7cRlQnk05WfswWdukOw9yjBkidsT1pJoiBQ==\",\\n            \"SigningCertUrl\":\"https://sns.eu-central-1.amazonaws.com/SimpleNotificationService-a86cb10b4e1f29c941702d7371d28f7b6.pem\",\\n            \"UnsubscribeUrl\":\"https://sns.eu-central-1.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5\",\\n            \"MessageAttributes\":{\\n\\n            }\\n         }\\n      }\\n   ]\\n}\\', \\'Timestamp\\': \\'2020-03-01T21:45:12.192Z\\', \\'SignatureVersion\\': \\'1\\', \\'Signature\\': \\'pt7Mkfo+CB5rsHAnWWB7Kb/LtgBCZSJWc2fLTB84FhZ9/MFUK0pOYmou97dAgn1hdo48JEXnQKpnMN5flmxwGEmG6SPHklnSAgE18a0Bv0qQgzQ1KF9PIY2ulRJiebbuE0gToTlDCgiUGd0OJpZ5Cdr4TSZgOpT4AcDD4NcpGCBKMTRwTcllaQDTNWF2mko9y6iqLp08ptq14qm4ppu9hrdGUU3klxE77Psn+7El6Cv3R8/asdfasdfaksdjhfiqwezhfknabsdfiugasdkf33==\\', \\'SigningCertUrl\\': \\'https://sns.eu-central-1.amazonaws.com/SimpleNotificationService-ashk38dn298djhxo8he2lknfO.pem\\', \\'UnsubscribeUrl\\': \\'https://sns.eu-central-1.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5\\', \\'MessageAttributes\\': {}}}]}",
                "Timestamp":"2020-03-02T00:20:06.458Z",
                "SignatureVersion":"1",
                "SigningCertUrl":"https://sns.eu-central-1.amazonaws.com/SimpleNotificationService-d3iiiffndoendii3mmmdi3.pem",
                "UnsubscribeUrl":"https://sns.eu-central-1.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-central-1:123456:sns-topic-dam-poc-new-import1:823baaf4-93b6-499a-944e-c99e1a6b1fb5",
                "MessageAttributes":{

                }
            }
        }
    ]
}

我可以在Message中看到bucket名称 这是我的python代码：

import boto3
def newImportHandler(event, context):
    print("__________")
    print(event)
    print("__________")
    simple1 = event['Records'][0]['Sns']['Message']
    print('Simple 1 '+simple1)
    simple2 = simple1['Records'][0]
    print('Simple 2 '+simple2)

simple1是一个字符串！所以这个代码失败了

Answer 1

为了再现你的情况，我做了以下工作：

• 创建了一个亚马逊S3 bucket
• 创建了一个Amazon SNS主题，并修改了权限以接受来自bucket的请求（取自Example Walkthrough: Configure a Bucket for Notifications）
• 创建了一个AWS Lambda函数，并订阅了SNS主题
• 在bucket上配置了一个Amazon S3事件，以向SNS主题发送消息
• 通过将文件上载到bucket进行测试

Lambda代码对我来说运行良好：

import json

def lambda_handler(event, context):
    
    message = json.loads(event['Records'][0]['Sns']['Message'])
    bucket = message['Records'][0]['s3']['bucket']['name']
    key = message['Records'][0]['s3']['object']['key']
    ...

Answer 2

我也收到了一个错误，根据AWS处理包含SNS消息的lambda事件的文档，这段代码应该是一个起点：

def lambda_handler(event, context):
    #print("Received event: " + json.dumps(event, indent=2))
    message = event['Records'][0]['Sns']['Message']
    print("From SNS: " + message)
    return message

但是，在我写这篇文章时，事件的实际格式要求访问如下消息：

string_msg = event['Records'][0]['Sns']['Message']
sns_msg = json.loads(string_msg)

然后，对于S3事件数据：

s3_event_data = sns_msg['Records'][0]['s3']

事件字典中的实际“Message”条目仍然是字符串化的JSON，需要加载它才能获得实际的S3事件数据