how to access AWS S3 from Lambda in VPC

0 votes

Overall, I'm pretty confused by using AWS Lambda within a VPC. The problem is Lambda is timing out while trying to access an S3 bucket. The solution seems to be a VPC Endpoint

I've added the Lambda function to a VPC so it can access an RDS hosted database (not shown in the code below, but functional). However, now I can't access S3 and any attempt to do so times out.

I tried creating a VPC S3 Endpoint, but nothing has changed.

VPC Configuration

I'm using a simple VPC created by default whenever I first made an EC2 instance. It has four subnets, all created by default.

VPC Route Table

_Destination - Target - Status - Propagated_ - local - Active - No

pl-63a5400a ( - vpce-b44c8bdd - Active - No - igw-325e6a56 - Active - No

Simple S3 Download Lambda:

import boto3
import pymysql
from StringIO import StringIO

def lambda_handler(event, context):
    s3Obj = StringIO()

    return boto3.resource('s3').Bucket('marineharvester').download_fileobj('Holding - Midsummer/sample', s3Obj)

Sep 28, 2018 in AWS by bug_seeker
• 14,980 points

1 answer to this question.

Your answer

Your name to display (optional):
Privacy: Your email address will only be used for sending these notifications.
0 votes

With boto3, the S3 urls are virtual by default, which then require internet access to be resolved to region specific urls. This causes the hanging of the Lambda function until timeout.

To resolve this requires use of a Config object when creating the client, which tells boto3 to create path based S3 urls instead:

import boto3 import botocore.config

client = boto3.client('s3', 'ap-southeast-2, config=botocore.config.Config(s3={'addressing_style':'path'}))

Note that the region in the call must be the region to which you are deploying the lambda and VPC Endpoint.

Then you will be able to use the pl-xxxxxx prefix list for the VPC Endpoint within the Lambda's security group, and still access S3.

Here is a working CloudFormation script that demonstrates this. It creates an S3 bucket, a lambda (that puts records into the bucket) associated to a VPC containing only private subnets and the VPC Endpoint, and necessary IAM roles.

answered Sep 28, 2018 by Priyaj
• 56,140 points

Related Questions In AWS

0 votes
2 answers

How to access files in S3 bucket from R?

You can take a look at the ...READ MORE

answered Aug 10, 2018 in AWS by Deepthi
• 300 points
0 votes
2 answers

How to create a VPC from scratch in AWS Console?

Creating a VPC from scratch is bit ...READ MORE

answered Feb 20 in AWS by Priyaj
• 56,140 points
+1 vote
1 answer
0 votes
2 answers
0 votes
1 answer
0 votes
1 answer
0 votes
1 answer

© 2018 Brain4ce Education Solutions Pvt. Ltd. All rights Reserved.
"PMP®","PMI®", "PMI-ACP®" and "PMBOK®" are registered marks of the Project Management Institute, Inc. MongoDB®, Mongo and the leaf logo are the registered trademarks of MongoDB, Inc.