aws cli lambda `update-function-configuration` deletes existing environment variables - amazon-web-services

Question

The documentation on the AWS cil lambda states that
...You provide only the parameters you want to change...
Which I assume means that the rest of the settings would still remain the same.
However, say my lambda function has environment variables :
var1=old_val1
var2=old_val2
var3=old_val3
and then when I try doing something like this :
aws lambda update-function-configuration --function-name dummy_fun --environment '{"Variables":{"var1":"new_val1","var2":"new_val2"}}'
with the intention of updating the variables :
var1 and var2 with the new values new_val1 and new_val2 respectively, although these 2 variables DO get updated, but the third one, var3, gets deleted !
Am I doing something wrong ? Or is there a way to make sure this doesn't happen?
I can definitely handle it using a workaround wherein I can fetch the current config and then update the env variables locally and then push the entire updated config, all of this through a python code etc.
But, is that the only way to do it ? Or can there be a simpler way of doing it?

Answer 1

You are misinterpreting the intention of the documentation.
You provide only the parameters you want to change.
--environment is the (singular) "parameter" that you are specifying should be changed -- not the individual variables.
The environment variables are configured en bloc so there is no concept of specifying only certain environment variables that you want to be different.

Answer 2

aws lambda update-function-configuration --function-name my-function-name --environment Variables="{VAR1=variable_value, VAR2=variable_value}"
Description:Above Command will update the environment variables for the lambda function in aws.

Answer 3

It seems not easy to partially update the environment variables for a lambda with awscli.
But with the usage of the built-in JSON-based client-side filtering that uses the JMESPath syntax, I found a way to achieve what I needed to do.
NEW_ENVVARS=$(aws lambda get-function-configuration --function-name your-func-name --query "Environment.Variables | merge(#, \`{\"ENV_VAR_TO_UPDATE\":\"value_here\"}\`)")
aws lambda update-function-configuration --function-name your-func-name --environment "{ \"Variables\": $NEW_ENVVARS }"
Of course, you can update more than one environment variable with that trick.

Answer 4

I had the same problem where I wanted to update only one env variable of a function and not touch the rest.
I ended up writing a script in node and publishing it:
https://www.npmjs.com/package/aws-lambda-update-env
It is pretty simple to use:
update-lambda-env KEY "My New Test Value" --stack-name myApplicationStack
This will only change the variable KEY in the functions located in the stack
myApplicationStack
A better solution might be to use AWS Parameter Store if your variable is going to change often.
https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-paramstore.html