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What could be the cause of low network throughput on my AWS lambda?

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My AWS lambda is fetching files that are a few 100mb and it takes roughly 1s per 1mb which seems incredibly slow. Memory is at 20% (2048mb), CPU is at 30%. Both the source and the lambda are on AWS network. My Lambda is on a VPC, and it has an additional security group to force it to get it's own ENI.

On my home WiFi in the same City as the AWS region I'm getting at least 7x faster download down from the source.

While this is happening a small putObject to S3 on a 58kb file can take upwards 20s to complete. It's very odd.

Where can I find how much bandwidth is to the lambda and what can I do to increase it?

Topics
Networking & Content Delivery
Tags
Amazon VPCNetworking & Content Delivery
Language
English
Kit - CostCenter
asked a year ago864 views
2 Answers
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Have you created an Interface VPC endpoint to S3 in your VPC. If you haven't the calls to S3 from the lambda function will be made over the Internet. If you have then the calls will be made over the Amazon network and will therefore be of much lower latency - https://docs.aws.amazon.com/AmazonS3/latest/userguide/privatelink-interface-endpoints.html

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Indranil Banerjee AWS
answered a year ago
  • Kit - CostCenter
    a year ago

    Thanks that's helpful, but my question isn't actually about the S3 upload, it's just odd to me that it's slow. The actual issue is that I'm fetching a file from a third party over HTTP, and only seeing around 1mb/s down even though my home network is doing 7mb/s down.

  • Indranil Banerjee AWS EXPERT
    a year ago

    How much memory is allocated to your lambda function? You can try increasing the memory to see if you get better performance.

  • Kit - CostCenter
    a year ago

    At 1GB I get 1mb/s. At 2GB I get 2mb/s. At max 10GB I get 2mb/s. Also I've confirmed there is a VPC Endpoint Gateway setup for S3 already, and it's mapped to the private subnet and the lambda can reach the gateway endpoint according to the reachability analyser.

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Hello, Indranil is correct in his comment, you should really set up a private gateway to s3 (https://docs.aws.amazon.com/vpc/latest/privatelink/vpc-endpoints-s3.html). It does not cost you anything, and it will increase network throughput while offloading your NAT.

However, the architecture you have should allow for faster traffic than you get, so my best guess would be the client transfer config, this is the python example, but every SDK (and the CLI) has its own version. https://boto3.amazonaws.com/v1/documentation/api/latest/guide/s3.html

Hope it helps!

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Carl Ostrand
answered a year ago
  • Kit - CostCenter
    a year ago

    Thanks but the issue isn't the S3 upload for the small file, but rather the download over http from a third party seem to choke at 1mb/s. I'm streaming multipart uploads on S3 so that's taken care of.

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