AWS Lambda (sdk) Encountering AliasNotFoundException when trying to access a Lambda function alias.

Understanding AWS Lambda

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. It executes your code only when needed and scales automatically, from a few requests per day to thousands per second. Lambda is designed to handle a variety of workloads, including data processing, real-time file processing, and more.

Identifying the Symptom

When working with AWS Lambda, you might encounter an error message stating AliasNotFoundException. This error typically occurs when you attempt to access a Lambda function using an alias that does not exist. The error message might look like this:

{ "errorMessage": "Alias not found", "errorType": "AliasNotFoundException"}

Explaining the Issue

The AliasNotFoundException is an error that arises when the specified alias for a Lambda function cannot be found. An alias in AWS Lambda is a pointer to a specific version of a Lambda function, allowing you to manage different environments (e.g., development, testing, production) more effectively. If the alias you are trying to use does not exist, AWS Lambda cannot resolve it to a function version, resulting in this exception.

Common Causes

• The alias name is misspelled or incorrect.
• The alias has been deleted or never created.
• The function name associated with the alias is incorrect.

Steps to Resolve AliasNotFoundException

To resolve the AliasNotFoundException, follow these steps:

Step 1: Verify Alias Existence

First, ensure that the alias you are trying to use actually exists. You can list all aliases for a specific Lambda function using the AWS CLI:

aws lambda list-aliases --function-name

Replace <your-function-name> with the name of your Lambda function. This command will return a list of aliases associated with the function. Verify that the alias you are trying to use is listed.

Step 2: Check Alias Spelling

Ensure that the alias name is spelled correctly in your code or configuration. Even a small typo can lead to the AliasNotFoundException.

Step 3: Create the Alias if Missing

If the alias does not exist, you need to create it. Use the following AWS CLI command to create a new alias:

aws lambda create-alias --function-name --name --function-version

Replace <alias-name> with your desired alias name and <version-number> with the version of the Lambda function you want the alias to point to.

Step 4: Update Alias if Necessary

If the alias exists but points to the wrong version, update it using:

aws lambda update-alias --function-name --name --function-version

This command updates the alias to point to the correct function version.

Additional Resources

For more information on managing Lambda aliases, refer to the AWS Lambda Developer Guide. If you need further assistance, consider visiting the AWS Lambda Forum for community support.