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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!

John Rotenstein
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Vinayak Rao
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2 Answers2

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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.

tino1b2be
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  • I believe the questioner wanted to resolve this inside AWS Lambda – Akber Iqbal Apr 14 '22 at 03:36
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    AWS Lambda doesn't provide the cryptography library for python so you have to package the library with your Lambda function, which means you have to package/compile it somewhere outside Lambda and then import it into Lambda. You can do it using some sort of CI/CD pipeline in or outside AWS but it can't be done inside AWS Lambda itself. – tino1b2be Apr 15 '22 at 14:11
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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

priyanshu kumar
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