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Parameters

The parameters utility provides high-level functions to retrieve one or multiple parameter values from AWS Systems Manager Parameter Store, AWS Secrets Manager, AWS AppConfig, Amazon DynamoDB, or bring your own.

Key features

  • Retrieve one or multiple parameters from the underlying provider
  • Cache parameter values for a given amount of time (defaults to 5 seconds)
  • Transform parameter values from JSON or base 64 encoded strings
  • Bring Your Own Parameter Store Provider

Getting started

By default, we fetch parameters from System Manager Parameter Store, secrets from Secrets Manager, and application configuration from AppConfig.

IAM Permissions

This utility requires additional permissions to work as expected.

Different parameter providers require different permissions

Provider Function/Method IAM Permission
SSM Parameter Store get_parameter, SSMProvider.get ssm:GetParameter
SSM Parameter Store get_parameters, SSMProvider.get_multiple ssm:GetParametersByPath
Secrets Manager get_secret, SecretsManager.get secretsmanager:GetSecretValue
DynamoDB DynamoDBProvider.get dynamodb:GetItem
DynamoDB DynamoDBProvider.get_multiple dynamodb:Query
App Config AppConfigProvider.get_app_config, get_app_config appconfig:GetConfiguration

Fetching parameters

You can retrieve a single parameter using get_parameter high-level function.

For multiple parameters, you can use get_parameters and pass a path to retrieve them recursively.

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from aws_lambda_powertools.utilities import parameters

def handler(event, context):
    # Retrieve a single parameter
    value = parameters.get_parameter("/my/parameter")

    # Retrieve multiple parameters from a path prefix recursively
    # This returns a dict with the parameter name as key
    values = parameters.get_parameters("/my/path/prefix")
    for k, v in values.items():
        print(f"{k}: {v}")

Fetching secrets

You can fetch secrets stored in Secrets Manager using get_secrets.

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from aws_lambda_powertools.utilities import parameters

def handler(event, context):
    # Retrieve a single secret
    value = parameters.get_secret("my-secret")

Fetching app configurations

New in 1.10.0

You can fetch application configurations in AWS AppConfig using get_app_config.

The following will retrieve the latest version and store it in the cache.

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from aws_lambda_powertools.utilities import parameters

def handler(event, context):
    # Retrieve a single configuration, latest version
    value: bytes = parameters.get_app_config(name="my_configuration", environment="my_env", application="my_app")

Advanced

Adjusting cache TTL

By default, we cache parameters retrieved in-memory for 5 seconds.

You can adjust how long we should keep values in cache by using the param max_age, when using get() or get_multiple() methods across all providers.

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from aws_lambda_powertools.utilities import parameters
from botocore.config import Config

config = Config(region_name="us-west-1")
ssm_provider = parameters.SSMProvider(config=config)

def handler(event, context):
    # Retrieve a single parameter
    value = ssm_provider.get("/my/parameter", max_age=60) # 1 minute

    # Retrieve multiple parameters from a path prefix
    values = ssm_provider.get_multiple("/my/path/prefix")
    for k, v in values.items():
        print(f"{k}: {v}")

Always fetching the latest

If you'd like to always ensure you fetch the latest parameter from the store regardless if already available in cache, use force_fetch param.

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from aws_lambda_powertools.utilities import parameters

def handler(event, context):
    # Retrieve a single parameter
    value = parameters.get_parameter("/my/parameter", force_fetch=True)

Built-in provider class

For greater flexibility such as configuring the underlying SDK client used by built-in providers, you can use their respective Provider Classes directly.

This can be used to retrieve values from other regions, change the retry behavior, etc.

SSMProvider

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from aws_lambda_powertools.utilities import parameters
from botocore.config import Config

config = Config(region_name="us-west-1")
ssm_provider = parameters.SSMProvider(config=config)

def handler(event, context):
    # Retrieve a single parameter
    value = ssm_provider.get("/my/parameter")

    # Retrieve multiple parameters from a path prefix
    values = ssm_provider.get_multiple("/my/path/prefix")
    for k, v in values.items():
        print(f"{k}: {v}")

The AWS Systems Manager Parameter Store provider supports two additional arguments for the get() and get_multiple() methods:

Parameter Default Description
decrypt False Will automatically decrypt the parameter.
recursive True For get_multiple() only, will fetch all parameter values recursively based on a path prefix.

Example

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from aws_lambda_powertools.utilities import parameters

ssm_provider = parameters.SSMProvider()

def handler(event, context):
    decrypted_value = ssm_provider.get("/my/encrypted/parameter", decrypt=True)

    no_recursive_values = ssm_provider.get_multiple("/my/path/prefix", recursive=False)

SecretsProvider

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from aws_lambda_powertools.utilities import parameters
from botocore.config import Config

config = Config(region_name="us-west-1")
secrets_provider = parameters.SecretsProvider(config=config)

def handler(event, context):
    # Retrieve a single secret
    value = secrets_provider.get("my-secret")

DynamoDBProvider

The DynamoDB Provider does not have any high-level functions, as it needs to know the name of the DynamoDB table containing the parameters.

Local testing with DynamoDB Local

You can initialize the DynamoDB provider pointing to DynamoDB Local using endpoint_url parameter:

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from aws_lambda_powertools.utilities import parameters

dynamodb_provider = parameters.DynamoDBProvider(table_name="my-table", endpoint_url="http://localhost:8000")

DynamoDB table structure for single parameters

For single parameters, you must use id as the partition key for that table.

id value
my-parameter my-value

Example

With this table, the return value of dynamodb_provider.get("my-param") call will be my-value.

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from aws_lambda_powertools.utilities import parameters

dynamodb_provider = parameters.DynamoDBProvider(table_name="my-table")

def handler(event, context):
    # Retrieve a value from DynamoDB
    value = dynamodb_provider.get("my-parameter")

DynamoDB table structure for multiple values parameters

If you want to be able to retrieve multiple parameters at once sharing the same id, your table needs to contain a sort key name sk.

For example, if you want to retrieve multiple parameters having my-hash-key as ID:

id sk value
my-hash-key param-a my-value-a
my-hash-key param-b my-value-b
my-hash-key param-c my-value-c

With this table, the return of dynamodb_provider.get_multiple("my-hash-key") call will be a dictionary like:

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{
    "param-a": "my-value-a",
    "param-b": "my-value-b",
    "param-c": "my-value-c"
}

Example

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from aws_lambda_powertools.utilities import parameters

dynamodb_provider = parameters.DynamoDBProvider(table_name="my-table")

def handler(event, context):
    # Retrieve multiple values by performing a Query on the DynamoDB table
    # This returns a dict with the sort key attribute as dict key.
    values = dynamodb_provider.get_multiple("my-hash-key")
    for k, v in values.items():
        print(f"{k}: {v}")

Additional arguments

The DynamoDB provider supports four additional arguments at initialization. These can be used if you require a custom table structure:

Parameter Mandatory Default Description
table_name Yes (N/A) Name of the DynamoDB table containing the parameter values.
key_attr No id Hash key for the DynamoDB table.
sort_attr No sk Range key for the DynamoDB table. You don't need to set this if you don't use the get_multiple() method.
value_attr No value Name of the attribute containing the parameter value.

Example

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from aws_lambda_powertools.utilities import parameters

dynamodb_provider = parameters.DynamoDBProvider(
    table_name="my-table",
    key_attr="MyKeyAttr",
    sort_attr="MySortAttr",
    value_attr="MyvalueAttr"
)

def handler(event, context):
    value = dynamodb_provider.get("my-parameter")

AppConfigProvider

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from aws_lambda_powertools.utilities import parameters
from botocore.config import Config

config = Config(region_name="us-west-1")
appconf_provider = parameters.AppConfigProvider(environment="my_env", application="my_app", config=config)

def handler(event, context):
    # Retrieve a single secret
    value: bytes = appconf_provider.get("my_conf")

Create your own provider

You can create your own custom parameter store provider by inheriting the BaseProvider class, and implementing both _get() and _get_multiple() methods to retrieve a single, or multiple parameters from your custom store.

All transformation and caching logic is handled by the get() and get_multiple() methods from the base provider class.

Here is an example implementation using S3 as a custom parameter store:

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import copy

from aws_lambda_powertools.utilities import BaseProvider
import boto3

class S3Provider(BaseProvider):
    bucket_name = None
    client = None

    def __init__(self, bucket_name: str):
        # Initialize the client to your custom parameter store
        # E.g.:

        self.bucket_name = bucket_name
        self.client = boto3.client("s3")

    def _get(self, name: str, **sdk_options) -> str:
        # Retrieve a single value
        # E.g.:

        sdk_options["Bucket"] = self.bucket_name
        sdk_options["Key"] = name

        response = self.client.get_object(**sdk_options)
        return

    def _get_multiple(self, path: str, **sdk_options) -> Dict[str, str]:
        # Retrieve multiple values
        # E.g.:

        list_sdk_options = copy.deepcopy(sdk_options)

        list_sdk_options["Bucket"] = self.bucket_name
        list_sdk_options["Prefix"] = path

        list_response = self.client.list_objects_v2(**list_sdk_options)

        parameters = {}

        for obj in list_response.get("Contents", []):
            get_sdk_options = copy.deepcopy(sdk_options)

            get_sdk_options["Bucket"] = self.bucket_name
            get_sdk_options["Key"] = obj["Key"]

            get_response = self.client.get_object(**get_sdk_options)

            parameters[obj["Key"]] = get_response["Body"].read().decode()

        return parameters

Deserializing values with transform parameter

For parameters stored in JSON or Base64 format, you can use the transform argument for deserialization.

The transform argument is available across all providers, including the high level functions

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from aws_lambda_powertools.utilities import parameters

def handler(event, context):
    value_from_json = parameters.get_parameter("/my/json/parameter", transform="json")

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from aws_lambda_powertools.utilities import parameters

ssm_provider = parameters.SSMProvider()

def handler(event, context):
    # Transform a JSON string
    value_from_json = ssm_provider.get("/my/json/parameter", transform="json")

    # Transform a Base64 encoded string
    value_from_binary = ssm_provider.get("/my/binary/parameter", transform="binary")

Partial transform failures with get_multiple()

If you use transform with get_multiple(), you can have a single malformed parameter value. To prevent failing the entire request, the method will return a None value for the parameters that failed to transform.

You can override this by setting the raise_on_transform_error argument to True. If you do so, a single transform error will raise a TransformParameterError exception.

For example, if you have three parameters, /param/a, /param/b and /param/c, but /param/c is malformed:

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from aws_lambda_powertools.utilities import parameters

ssm_provider = parameters.SSMProvider()

def handler(event, context):
    # This will display:
    # /param/a: [some value]
    # /param/b: [some value]
    # /param/c: None
    values = ssm_provider.get_multiple("/param", transform="json")
    for k, v in values.items():
        print(f"{k}: {v}")

    # This will raise a TransformParameterError exception
    values = ssm_provider.get_multiple("/param", transform="json", raise_on_transform_error=True)

Passing additional SDK arguments

You can use arbitrary keyword arguments to pass it directly to the underlying SDK method.

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from aws_lambda_powertools.utilities import parameters

secrets_provider = parameters.SecretsProvider()

def handler(event, context):
    # The 'VersionId' argument will be passed to the underlying get_secret_value() call.
    value = secrets_provider.get("my-secret", VersionId="e62ec170-6b01-48c7-94f3-d7497851a8d2")

Here is the mapping between this utility's functions and methods and the underlying SDK:

Provider Function/Method Client name Function name
SSM Parameter Store get_parameter ssm get_parameter
SSM Parameter Store get_parameters ssm get_parameters_by_path
SSM Parameter Store SSMProvider.get ssm get_parameter
SSM Parameter Store SSMProvider.get_multiple ssm get_parameters_by_path
Secrets Manager get_secret secretsmanager get_secret_value
Secrets Manager SecretsManager.get secretsmanager get_secret_value
DynamoDB DynamoDBProvider.get dynamodb (Table resource)
DynamoDB DynamoDBProvider.get_multiple dynamodb (Table resource)
App Config get_app_config appconfig get_configuration
Last update: 2021-04-05