Unable to Access Environment Variables in Lambda Function

Question

I want to access environment variables from within my lambda function, however I've been having issues with accomplishing that.

I use serverless to manage the creation and deployment of my lambda functions. Within one of the function definitions in my serverless file I have defined 2 environment variables:

functions:
    update-item:
        handler: ...
        environment:
            FUNCTION_NAME: updateItemById
            TOPIC_NAME: ${self:custom.topicName}
        events: ...

Within my lambda function I access the environment variable TOPIC_NAME like so:

Optional<String> topicName = Optional.of(System.getenv("TOPIC_NAME"));

This code throws an exception every time the lambda function executes because the TOPIC_NAME environment variable doesn't exist. However, I can see that the environment variable exists in:

The serverless.yml file
The CloudFormation files that serverless generates
The CloudFormation files as shown in the AWS console
The lambda function as shown in the AWS console

Within the lambda function I use a small loop to print out all of the environment variables:

Map<String, String> envVars = System.getenv();
for (String s : envVars.keySet()) {
    System.out.println(s + " - " + envVars.get(s));
}

The FUNCTION_NAME environment variable is displayed, however the TOPIC_NAME variable is not. I've tried renaming, adding, and removing environment variables and there is no change to the output of this print loop. I've re-deployed my code numerous times, with and without code changes, with config file changes, I've manually added the environment variable through the console. I've verified that the latest version of the lambda function is running. Nothing I've done has worked.

Based on the behavior it seems like the container that my lambda function is running in is never being refreshed and thus always contains the old environment variables. However, this runs contrary to everything I've read and how I expect lambda containers to work.

Mike Vanbuskirk · Accepted Answer · 2020-08-12 19:35:17Z

3

${self:custom.topicName}

You need to make sure you have the following top-level reference configured in your serverless.yml:

...
provider: aws
custom:
  topicName: <some-topic-name>

answered Aug 12, 2020 at 19:35

Mike Vanbuskirk

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2 Comments

Puffin Over a year ago

This does exist in my serverless file. The environment variable is successfully generated by serverless; it's in the CloudFormation files and shows as being present on the Lambda function according to the AWS console. It just doesn't exist inside the lambda function itself.

Mike Vanbuskirk Over a year ago

@Puffin - so even manually adding the variable to the UI doesn't return an output from the loop? Can you link a paste to your complete serverless.yml(sensitive data obfuscated as needed).

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