I am trying to have an architecture with:
Route53 <-> API gateway <-> Lambda <-> RDS and DynamoDB.
I am confused about some networking aspects here!
From most of the documentation, what I understand is that Lambda is by default launched in default VPC and can access internet from there but no resources inside a "VPC". And this 2nd VPC (in quotes) refers to non-default VPCs in most discussions. But what is not clear is what if I placed the Lambda and RDS both in default VPC, lambda in a public subnet with --vpc-config info and RDS in a private subnet, will my Lambda have the internet connection?
Even when everything is in default subnet, should I put my lambda function in to a private subnet with Internet access through an Amazon VPC NAT gateway?
I know it is a theoretical question - documents are confusing me by not explicitly mentioning what cannot be done!
From most of the documentation, what I understand is that Lambda is by
default launched in default VPC and can access internet from there but
no resources inside a "VPC".
That is incorrect. By default Lambda is not launched in a VPC at all. Or if it is in a VPC it is in one that you cannot see because it doesn't exist in your AWS account.
what if I placed the Lambda and RDS both in default VPC, lambda in a
public subnet with --vpc-config info and RDS in a private subnet, will
my Lambda have the internet connection?
No, your Lambda function will not have internet access, even in a public subnet. This is because it is never assigned a public IP address. Once you place a Lambda function inside a VPC you have to have a NAT gateway in order to for the Lambda function to access anything outside the VPC.
Even when everything is in default subnet, should I put my lambda
function in to a private subnet with Internet access through an Amazon
VPC NAT gateway?
Yes, that is the correct way to provide a Lambda function with access to both a VPC and resources that exist outside the VPC.
Also note that DynamoDB (and the AWS API) does not run in your VPC. So if you place a Lambda function inside your VPC that needs to access DynamoDB, or anything else that is accessed via the AWS API, you will have to add a NAT gateway to the VPC.
Note that the "Default VPC" is the term for a the VPC that is setup for you when you first create your AWS account. You can see this VPC in your account in the VPC service console. Aside from it being created for you with default settings, you should just think of this as another VPC in your account. The Default VPC is not used by Lambda when you don't specify a VPC, and it is not used by other services like DynamoDB that exist outside your VPC network.
Related
I have the following AWS VPC configuration:
2 public subnets
2 private subnets
Cloudfront is in front of the load balancer. The load balancer is linked to the public subnets and my RDS database reside in the private subnets.
What i want to accomplish is:
Create an API Gateway (publicly accessible) but restricted to only a specific IP address that can access it. The API Gateway is connected to a lambda function that, when called/triggered, the function must update some table data of my (private) RDS Postgres instance.
From my understanding the first step would be to create an IAM role for the lambda function to be only accessible by the IP address mentioned above.
Now what is the best way to access a private RDS from that lambda connected to API Gateway? Especially without using Nat Gateway because of the crazy cost associated to it.
Can someone help me just figure out how to do it, i am referring to the high level understanding how to do it?
As Norman said in their comment, you can control access to your API in API Gateway, and limit it to certain IP addresses, with API Gateway Resource Policies. This will at the same time control access to your Lambda that's behind that API.
You can then edit the Lambdas Configuration -> VPC setting and add it to a subnet that has access to your RDS database (and put it either in the same subnet as the database, or another subnet that has access permissions to the RDS subnet). To connect your Lambda to a VPC, the Lambda execution role will need the following permissions
ec2:CreateNetworkInterface
ec2:DescribeNetworkInterfaces
ec2:DeleteNetworkInterface
They are for example included in the managed policy AWSLambdaVPCAccessExecutionRole. Here you can read more about configuring a Lambda for VPC access.
I have a VPC containing 2 Lambda functions A & B:
A is on 2 public subnets
B is on 2 private subnets with a RDS Database instance
The VPC itself has Internet access via the NAT instance.
I need a 3rd party API to communicate with B, but B is in a private subnet. Now I was wondering whether API Gateway solves this problem or whether it requires more work.
Thanks in advance
If you want the 3rd-party to invoke the Lambda function and pass data to it, then AWS API Gateway is correct for the task. That is exactly what API Gateway is designed to do.
See: Using AWS Lambda with Amazon API Gateway - AWS Lambda
Alternatively, you could use an Elastic Load Balancer and have it invoke the Lambda function.
From: Using AWS Lambda with an Application Load Balancer - AWS Lambda
You also mention that you have an AWS Lambda "on 2 public subnets". AWS Lambda functions should not be configured to connect to public subnets. They should either be configured to use "No VPC" (in which case they can directly access the Internet), or they should be connected to private subnets (and can use a NAT Gateway or NAT Instance to access the Internet if required).
See: Configuring a Lambda function to access resources in a VPC - AWS Lambda:
Connect your function to private subnets to access private resources. If your function needs internet access, use network address translation (NAT). Connecting a function to a public subnet doesn't give it internet access or a public IP address.
As the title suggests, I placed my Lambda function in a private subnet and now It cannot access or timeout when scanning the DB. Prior to this, it could access and scan the DB. What should I do?
Your DynamoDB resources are not in your VPC. Since you've configured your Lambda functions to connect to your VPC, you need to setup a NAT Gateway or NAT Instance to allow your private resources to access the internet. As the docs state:
AWS Lambda uses the VPC information you provide to set up ENIs that
allow your Lambda function to access VPC resources. Each ENI is
assigned a private IP address from the IP address range within the
Subnets you specify, but is not assigned any public IP addresses.
Therefore, if your Lambda function requires Internet access (for
example, to access AWS services that don't have VPC endpoints), you
can configure a NAT instance inside your VPC or you can use the Amazon
VPC NAT gateway. You cannot use an Internet gateway attached to your
VPC, since that requires the ENI to have public IP addresses.
AWS Lambda Doc
Validate the following:
The route table for the Lambda has a NAT Gateway for internet traffic that resides in public subnet.
DynamoDB Gateway endpoint exists? Check its policy to ensure that it is not limited to specific sources
Outbound access is allowed via the security group and NACL
I have an AWS lambda function that makes a request to the internet. When it makes the request with NO VPC, it's ok, but when I add it to the VPC, it stops working. I've attached an Internet Gateway to the VPC and created a NAT Gateway with RT to use outbound 0.0.0.0/0, but it stills not working.
With the 15seconds timeout, it's always throwing TO.
Could you please help me?
I've already followed these sites:
https://gist.github.com/reggi/dc5f2620b7b4f515e68e46255ac042a7
http://derpturkey.com/lambda-vpc-and-internet-access-configuration/
Everything seems to be well configured.
Lambda configuration
Route Table configuration
IGW attached to VPC
There are three ways to grant Internet access to an AWS Lambda function:
Do not assign it a VPC, or
Assign it to a VPC and attach an Elastic IP Address to the ENI (Elastic Network Interface) that is created in the VPC, or
Assign it to a private subnet in a VPC and use a NAT Gateway to grant the private subnet access to the Internet
If you have already verified the network configurtions like VPC setup, Subnets, Route Table, IG/NAG gate way. And associated the Lambda with current subnet and security groups.
Then the last thing to verify would be:
For Lambda functions to work into custom or User Defined VPC, Adding Lambda to the VPC would require AWSLambdaVPCAccessExecutionRole in addition to AWSLambdaBasicExecutionRole.
Ensure that the associated role has the above permissions.
Source:
https://docs.aws.amazon.com/lambda/latest/dg/vpc-rds-create-iam-role.html
My setup is:
S3 (website) -> API Gateway -> Lambda -> RDS
-> S3 (configuration)
-> Shopify
-> Transactional Mail
I have an Internet Gateway set up to allow access to my S3 configurations and I need to hook up a NAT to allow me to make my calls out to 3rd parties. I've attempted to only use the NAT (per this question) by changing my Routing Table entry for 0.0.0.0/0 -> {my NAT}, but that just results in not being able to access my S3 configuration bucket.
Any help would be greatly appreciated!
Edit: To be clear I've read the documentation, what I'm having issues understanding is the relationships between the Security Group my Lambdas and RDS share, and the Subnets they're associated with.
When I configure my lambda to be part of the security group my RDS instances is in, I need to associate it with at least 2 subnets... Should those be new subnets, and not the ones associated with my RDS instances? AKA does a lambda need to share a subnet with an RDS in order to access it?
If the Lambda function only needs to access VPC resources and S3, then the easiest way to configure this is to add an S3 Endpoint to your VPC. If your Lambda function needs to access VPC resources plus other resources besides S3 and DynamoDB (the only 2 services that currently support VPC endpoints) then your Lambda function has to be in a private subnet with a NAT Gateway.
Instances in a public subnet have the option of having a public IP address, but it isn't a requirement. Lambda functions in a VPC do not ever get public IP addresses, which is why Lambda functions inside a VPC have to be in a private subnet with NAT gateway in order to have Internet access.
The only time Lambda functions get a public IP is when they are not in a VPC at all. In that instance they can access anything except resources in your VPC.
A note about your "same security group" comment: Being in the same security group does not allow resources to access each other. The Lambda function needs to be in a security group that the RDS security group has granted access to. Regarding subnets, the Lambda simply needs to be in any subnet in the same VPC, it does not need to be in the same subnet as the RDS instance.