it is possible to call a lambda function that lives within a VPC from another lambda in another VPC.
I'm trying to do it with an AWS VPC Endpoint but I can't do it. It marks error 403. I am following these steps: https://aws.amazon.com/es/blogs/compute/introducing-amazon-api-gateway-private-endpoints/.
And https://cedrus.digital/aws-privatelink-with-api-gateway-and-lambda-functions/
I am not sure, if the VPC Endpoint should be created in the VPC where the lambda will be called or where it will receive the request.
Even, the API Gateway Resource Policies has put it like this:
{
"Statement": [
{
"Principal": "*",
"Action": [
"execute-api:Invoke"
],
"Effect": "Allow",
"Resource": "*"
}
]
}
And the VPC endpoint policy to Full access.
To invoke an AWS Lambda function via an API call, the calling entity must have access to the Internet. It doesn't matter whether the calling entity is in the same VPC, a different VPC, or even not in a VPC. All that matters is that the request can be sent to the AWS Lambda API endpoint.
If the calling Lambda function is in a VPC, make sure that it has access to the Internet. This typically requires:
The Lambda function is in a private subnet
There is a NAT Gateway in a public subnet
The Route Table for the private subnet directs 0.0.0.0/0 traffic to the NAT Gateway
Alternatively, if the calling Lambda function is not connected to a VPC, then it automatically receives access to the Internet.
It also does not matter to what the "called" Lambda function is connected (VPC or not). The control plane that activates this Lambda function is on the Internet, which is unrelated to where the Lambda function itself is connected.
There are few ways that you can invoke a lambda from another lambda.
Lambda invokes other lambda directly
when you invoke a lambda(caller) from another lambda(callee) using aws-sdk's invoke function, as mentioned on a answer already, the lambda(caller) should have internet connectivity. because aws-sdk calls are by default made over the internet.
Therefore either the lambda should be deployed on a public subnet (not recommended) or you should have a Nat Gateway (or Nat instance is cheaper), so that the lambda can invoke the other lambda over the internet.
Lambda invokes the other lambda through Api Gateway
You don't even need to consider this option if the calling lambda has internet connectivity.
You can indeed create a private VPC endpoint for api gateway in the destination lambda end. Then the calling lambda can make a https call via the VPC endpoint's dns url.
For this to work, your VPC endpoint should be accessible from the other VPC from where you are going to make the http call.
therefore a vpc peering between the VPCs will make it possible. The good news is VPC endpoints are now accessible through vpc peering.
Hope this helps.
Reference:
https://aws.amazon.com/about-aws/whats-new/2019/03/aws-privatelink-now-supports-access-over-vpc-peering/
Related
I have a Lambda function deployed into a public subnet in a VPC and I’m trying to connect to a Lambda function outside of a VPC and I’m running into connectivity issues.
I believe the security group settings and IAM policies will permit the connection, but I'm not sure if there's an issue with connecting to an out-of-VPC Lambda from an in-VPC one.
Is there a tool in AWS Console, AWS CLI or anywhere else that I can use to troubleshoot where the connection is failing? I’ve used the Reachability Analyzer before but it only works on a handful of resource types like EC2 instances.
I've tried invoking the out-of-VPC Lambda from inside my in-VPC Lambda, but the request doesn't work and I don't see any helpful information about what happened. I tried running the Reachability Analyzer, but it doesn't allow you to test if Lambda functions are reachable.
I was expecting the request to work, but I'm not sure if I need to configure a VPC interface endpoint because I'm connecting from an in-VPC Lambda to an out-of-VPC Lambda.
I’m new to networking and would appreciate any help.
I have a Lambda function deployed into a public subnet in a VPC and I’m trying to connect to a Lambda function outside of a VPC and I’m running into connectivity issues.
The Lambda function in the VPC never gets a public IP assigned to it. So it can't connect to anything outside of the VPC. It can't use the Internet Gateway attached to the public subnet because it doesn't have a public IP.
By "connect to a Lambda function outside of a VPC" what you are really doing is connecting to the AWS API outside of the VPC. You never "connect" to a Lambda function, because Lambda functions aren't running and just sitting around idle waiting for your request. Lambda functions don't really exist until a request comes in to the AWS Lambda Invoke API, at which point AWS spins up an instance of the Lambda function and passes it the invocation payload.
To fix this connectivity issue, you either need to create an AWS Lambda VPC Endpoint in your VPC, to handle requests to the Lambda API originating in your VPC. Or you need to move the VPC Lambda function to a private subnet, with a route to a NAT Gateway. Lambda functions in private subnets can access things outside the VPC by having their requests routed through the NAT Gateway.
I was expecting the request to work, but I'm not sure if I need to configure a VPC interface endpoint because I'm connecting from an in-VPC Lambda to an out-of-VPC Lambda.
That's not how VPC Interface Endpoints work. The entire purpose of VPC Interface Endpoints is to allow a resource inside your VPC to access part of the AWS API that exists outside the VPC. A VPC Interface Endpoint will absolutely allow your Lambda function running in the VPC to access the Lambda Invoke API, in order to trigger an execution of your out-of-VPC Lambda function.
Given an AWS Lambda that does not need access to resources within a VPC, the well architected serverless lens recommends not putting the function in a VPC.
However, my Lambda will sit behind an APIGateway to facilitate a REST endpoint that needs to be accessed by servers that do sit within a VPC.
How can a VPC-less Lambda sit behind an APIGateway that itself is accessible within a VPC?
I would prefer that my APIGateway not be exposed to the public internet, therefore instantiating a public APIGateway and calling that public IP address from within my VPC via Nat gateway is not an acceptable solution.
Thank you in advance for your consideration and response.
Invoking an AWS Lambda function will always be done via the public AWS API. It doesn't matter if the Lambda function is configured to run in the VPC once it is invoked, it still has to be invoked via the public AWS API.
AWS Lambda functions do not sit running idle in your VPC waiting for an invocation request to come in. The whole point of Lambda functions is that they do not exist at all until they are needed to process a request, at which point the AWS infrastructure creates an instance of your function, and then passes it the request info to process.
If you add an AWS Lambda function to your VPC, all that does is attach an ENI from your VPC to the Lambda function at the time it is executing, so that it can use the network connection provided by that ENI to access resources inside your VPC.
The API Gateway service itself also does not run inside your VPC. Both API Gateway and Lambda exist outside your VPC, and API Gateway will have no problems accessing the public AWS API to invoke a Lambda function.
When you make your API Gateway VPC only, the API Gateway service (servers) still exists outside the VPC, it just makes the API Gateway accessible at a private address inside your VPC, via a network gateway to the API Gateway service.
I have lambda function which needs to access RDS in isolated private subnet.
And lambda function also need to access internet endpoint and be invoked from internet.
In this case,
put lambda in private subnet (with Nat gateway)
lambda can access internet from nat gateway
However ,,, is it possible to invoke lambda function in private subnet from internet?
(I can set API gateway to the lambda in private subnet?)
"However ,,, is it possible to invoke lambda function in private
subnet from internet?"
Yes, you always invoke Lambda from the AWS API, which is on the public Internet. Then AWS creates an instance of your Lambda function to handle the invocation. You never make a direct network connection to a Lambda function. It doesn't matter if your Lambda function is configured to run inside your VPC, you still invoke it the same way.
I have a lambda function that calls the parameter store to retrieve a credential. The code is as follows:
import boto3
ssm = boto3.client('ssm')
parameter = ssm.get_parameter(Name='credentials', WithDecryption=True)
print(parameter['Parameter']['Value'])
I have given AmazonSSMFullAccess to the lambda role. The lambda has a VPC which later I'll use it to connect to a Redshift database without public access. The inbound and outbound rules are as follows:
There is a post AWS Lambda cannot connect to Parameter Store which mentions that if the lambda requires VPC, then add a NAT gateway.
In the lambda subnet route table: , there seems to be already a route that goes to the internet?
But I am still getting lambda time-out errors :(
there seems to be already a route that goes to the internet?
Sadly, it does not. It seems you placed your lambda in a public subnet with route to internet gateway (IGW). However, you have to use private subnet with a route to NAT gateway. IGW and NAT are two different things. Have a look at this AWS guide how to make it work:
How do I give internet access to a Lambda function that's connected to an Amazon VPC?
Alternatively, you can setup VPC interface endpoint for Paramter store. Then you don't need internet access for your Lambda function.
I've been trying to connect to S3 bucket from a lambda residing in a private subnet. I did the exact same thing for Ec2 instance and it worked like a charm, I'm not sure why with lambda it's such an issue. My lambda times out after a certain defined interval.
Here's my lambda's VPC configuration
Here's the security group output configuration:
Below are the outbound rules of the subnet associated with lambda
As you can see, I created a VPC endpoint to route my traffic through the VPC but it doesn't work. I'm not sure what am I missing here. Below is the VPC Endpoint configuration.
I've given full access to S3 in policy like this:
{
"Statement": [
{
"Action": "*",
"Effect": "Allow",
"Resource": "*",
"Principal": "*"
}
]
}
When I run my lambda code, I get timeout error as below:
You can access Amazon S3 objects using VPC endpoint only when the S3 objects are in the same Region as the Amazon S3 gateway VPC endpoint. Confirm that your objects and endpoint are in the same Region.
To reproduce your situation, I performed the following steps:
Created an AWS Lambda function that calls ListBuckets(). Tested it without attaching to a VPC. It worked fine.
Created a VPC with just a private subnet
Added an Amazon S3 Endpoint Gateway to the VPC and subnet
Reconfigured the Lambda function to use the VPC and subnet
Tested the Lambda function -- it worked fine
I suspect your problem might lie with the Security Group attached to the Lambda function. I left my Outbound rules as "All Traffic 0.0.0.0/0" rather than restricting it. Give that a try and see if it makes things better.