AWS Lambda python function 从 S3 解析 json 并存储在 DynamoDB

Question

I'm trying to write a lambda function that is triggered whenever a json file is uploaded to an s3 bucket. The function is supposed to parse the file and store it immediately in DynamoDB. I created a table called 'data' with the primary key set as 'date'. Here's what I have for the function so far:

import boto3
import json
s3_client = boto3.client('s3')
dynamodb = boto3.resource('dynamodb')

def lambda_handler(event, context): 
   bucket = event['Records'][0]['s3']['bucket']['name']
   json_file_name = event['Records'][0]['s3']['object']['key']
   json_object = s3.Bucket(bucket).Object(json_file_name)
   jsonFileReader = json_object['Body'].read()
   jsonDict = json.loads(jsonFileReader)
   table = dynamodb.Table('data')
   table.put_item(Item = jsonDict)

Here is an example of a json file I'm trying to use:

{
 "date": "2020-06-07 21:00:34.284421",
 "ConfirmedCases": 7062067,
 "ActiveCases": 3206573,
 "RecoveredCases": 3450965,
 "Deaths": 404529
}

Unfortunately, whenever I test the code, it throws this error:

[[ERROR] TypeError: string indices must be integers
Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 7, in lambda_handler
    bucket = event'Records'][0]['s3']['bucket']['name']]

Does anyone know how to resolve this issue? I've wasted so much time trying to figure this out and I still am unable to:/

Answer 1

Your error is from either of these lines.

bucket = event['Records'][0]['s3']['bucket']['name']
json_file_name = event['Records'][0]['s3']['object']['key']

However, they are correct . This is the valid way of access bucket name and object key from the event generated by S3 Notifications.

It seems to me that something else is trigger your function . Either you use Test option in the console and provide incorrect event object, or there is some other event that triggers the lambda with non-S3 event.

As a quick fix, you can do the following. The code below will finish if event object does not contain Records :

def lambda_handler(event, context): 

    if 'Records' not in event:
        print(event) # good to check what event you get  
        return

    # and the rest of code