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"AWS Lambda Python Function Error: 'cryptography package is required for sha256_password or caching_sha2_password auth methods' - Function Stopped Working After Several Days"

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I'm writing a Python Lambda function in AWS Lambda. However, I'm getting an error that says 'cryptography package is required for sha256_password or caching_sha2_password auth methods'. The Lambda is defined in CDK, and the Layers Path structure is 'layers/common_layer/python/cryptography'. Libraries including pymysql and cryptography are installed. What's most puzzling is that the Lambda function was initially working fine, but it stopped working after 2-3 days. I downloaded the layer from the AWS Console's layer menu, and the libraries in it appeared to be properly configured. I'm asking because I'm unable to identify what the problem might be.

  • Blowfish
    a year ago

    After that, on AWS EC2 (Amazon Linux 2023), I installed pymysql and cryptography and regenerated _cffi_backend.cpython-312-x86_64-linux-gnu.so. I then correctly placed this in Layers and deployed it using CDK. Initially, the error disappeared, and it seemed to run normally. However, a day later, running it under the exact same conditions, the same error reappeared, and I have absolutely no idea why. What could be the possible causes for this?

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asked a year ago955 views

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The error you're encountering suggests that the Lambda function is unable to find or load the cryptography package, which is required for certain authentication methods when connecting to a database (likely MySQL in this case). The fact that it worked initially but stopped after a few days points to a potential issue with how the Lambda environment is handling your layer or dependencies.

Here are a few potential reasons and solutions to consider:

  1. Layer incompatibility: Ensure that the Python version used to create the layer matches the runtime of your Lambda function. If there's a mismatch, it could lead to compatibility issues.

  2. Layer size limits: Check if your layer size is within the Lambda limits. If it's too large, it might not be applied correctly.

  3. Lambda caching: Lambda may cache parts of your function for performance reasons. Sometimes, this caching can cause issues with dependencies. Try redeploying your function or updating it to force a fresh environment.

  4. Incorrect layer structure: Verify that your layer structure is correct. The cryptography package should be in the python/lib/python3.x/site-packages/ directory within your layer zip file.

  5. Permissions: Ensure that your Lambda function has the necessary permissions to access the layer.

  6. Lambda updates: AWS occasionally updates the Lambda execution environment. These updates could potentially affect how your dependencies are loaded.

To troubleshoot:

  1. Double-check your layer structure and ensure it's correctly zipped.
  2. Try including the cryptography package directly in your Lambda deployment package instead of using a layer.
  3. Update your Lambda function (even with a minor change) to force a redeployment.
  4. Check your function's logs for any additional error messages that might provide more context.
  5. Verify that the cryptography package version in your layer is compatible with your Python runtime and other dependencies.

If the issue persists, you might want to consider using a Lambda container image instead of layers. This approach gives you more control over the execution environment and can help avoid some of the complexities associated with layers.

Sources
Unable to import module 'lambda_function': No module named 'requests | AWS re:Post
Why am I unable to install any dependencies to Lambda Via Layers? | AWS re:Post
Troubleshoot deployment issues in Lambda - AWS Lambda

answered a year ago

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