Bug: parameters confusing is combining get_parameter and get_parameters results

[beck3905]

Expected Behaviour

Given SSM parameters:

• /foo/bar/param1
• /foo/bar/param2
• /foo/bar/param3

Calling parameters.get_parameters("/foo/bar") should return a dictionary of all 3 parameters.
Calling parameters.get_parameter("/foo/bar") should ALWAYS raise a GetParameterError. This error should be raised even if the get_parameter call comes after the get_parameters call.

Current Behaviour

Given the same parameters as above:

If I call parameters.get_parameters("/foo/bar") all 3 parameters are cached under the parameter /foo/bar and returned as a dictionary.
If I subsequently call parameters.get_parameter("/foo/bar") it returns the same dictionary as the get_parameters call instead of raising the GetParameterError.

Code snippet

# Update paths below to PATH of actual SSM parameters in your account and not parameter NAMES.


from aws_lambda_powertools.utilities import parameters

print(parameters.get_parameters(path="/foo/bar"))
print(parameters.get_parameter("/foo/bar"))

Possible Solution

• Cache get_parameter results separately from get_parameters results.
• Note in the cache whether the values being cached are from get_parameter or get_parameters.

Steps to Reproduce

1. Add multiple SSM parameters to parameter store under the same path.
2. Run Code Snippet above referencing the SSM parameters' path.

Powertools for AWS Lambda (Python) version

latest

AWS Lambda function runtime

3.9

Packaging format used

Lambda Layers

Debugging logs

No response

[rubenfonseca]

Looking at this now

[rubenfonseca]

I have a couple of ideas, and will follow up tomorrow morning

[rubenfonseca]

@beck3905 I'm looking at this again, and I'm wondering what's the use case that requires you to use both get_parameters and get_parameter with the same key. Can you expand a little on what are you trying to achieve? I need to understand the problem a little bit better in order to help the best way possible :)

[beck3905]

@beck3905 I'm looking at this again, and I'm wondering what's the use case that requires you to use both get_parameters and get_parameter with the same key. Can you expand a little on what are you trying to achieve? I need to understand the problem a little bit better in order to help the best way possible :)

@rubenfonseca I have a config class in my code that reads all my parameters from SSM on load and adds them as attributes of my config class. The code that loads the SSM parameters reads both individual parameters by name or multiple parameters by path. It does this by wrapping the get_parameter call in a try/except and then in the except block calling get_parameters.

For example, let's say I have an SSM path of /dev/auth and I have SSM parameters /dev/auth/client-id and /dev/auth/client-secret. The config class would look up all parameters under /dev/auth by first attempting to get_parameter("/dev/auth"). This would raise an exception and then the config class would call get_parameters("/dev/auth"). Once it receives the parameters it loops through them and adds them as attributes of the class so that I can call config.auth_client_id and config.auth_client_secret.

I ran into this issue because multiple modules will load the config class and get different values. So the first module to load the config class will go through the process above and get the correct parameter values to use locally. However, the second module to load the config class will call get_parameter("/dev/auth") and get the dictionary {"client-id": ..., "client-secret": ...} instead of raising an exception. Then the individual parameters under /dev/auth do not get added correctly as attributed to my config class in that second module.

[leandrodamascena]

Hi @beck3905! Thanks for explaining in detail your use case and what we can to help you.

We agree that we should split caching between single fetch and multi fetch to avoid errors like this one. Do you have the bandwidth to send a PR fixing this? It would be awesome to have your code contribution to the Powertools project.