AWS Lambda: cannot import name 'asn1'

Question

I am using pysftp to connect to a sFTP site from a python function. This is working fine from my local that is running as file_track.py. But when I deploy that on AWS lambda it is failing with –

{
  "error Message": "Unable to import module 'lambda function': cannot import name 'asn1' from 'cryptography.hazmat.bindings._rust' (unknown location)",
  "error Type": "Runtime.ImportModuleError",
  "requestId": "0235edb8-25a3-4570-a1ea-2a2696a7dd04",
  "stack Trace": []
}

Please help me out!

Answer 1

I experienced this error even after following the AWS guide on how to compile lambda functions with extra dependencies. After getting stuck for hours, it turns out to be a difference in the CPU architecture between my personal laptop and the lambda function's runtime environment. My personal laptop is an Asus TUF A15 which is using an x64 AMD Ryzen 7 4800H CPU. However, my Lambda function's runtime was Python 3.8 on x86_64 which is an Intel CPU. The cryptography library packages I was downloading and packaging on my AMD CPU are not compatible with the Intel CPU. Most other libraries work fine though but apparently not the cryptography library.

Solution:

I launched a temporary m5.large EC2 instance running x86_64 AMI for Amazon Linux 2022 (can be a T2, I don't think it matters as long as it's x86_64), then followed the same steps specified on this doc and my function executed successfully without any issues.

Answer 2

I seems that you have not packed your pysftp python package with your lambda function hence it is unable to find the bindings you can try forming layers this is a similar type of issue that might help you

pysftp library not working in AWS lambda layer