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lambda-configuration.md

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Lambda Configuration

µServerless supports three methods to get configuration values: environment variables, SSM Parameter Store, and Noop

By default the lambda handlers require you to implement the methods defined in the LambdaConfiguration trait. You can satisfy this requirement by simply extending your function with one of the provided traits:

  • SsmLambdaConfig
  • EnvLambdaConfig
  • NoopLambdaConfig

Usage

Functions can retrieve configuration values using the following methods:

Get Values

getValue(name: String): Option[String]

Name is the fully qualified name and includes the hierarchy of the parameter path and name. For the env vars a value like /database/password will be converted to DATABASE_PASSWORD

Get Paths

getValues(path: String): Map[String, String]

Here the path is a partial path. This will return a map of values containing key -> values for all the elements in the hierarchy. For name like /database the method may return all the database related values such as /database/username, /database/password, etc.

EnvLambdaConfig

This trait comes bundled with µServerless and can be used by extending the EnvLambdaConfiguration trait like such

class TestFunction(snsClientMock: AmazonSNSAsync) extends LambdaHandler with EnvLambdaConfiguration {
  val foo: Option[String] = getValue("/foo")
  val barHierarchy: Map[String, String] = getValues("/bar/")
}

SsmLambdaConfig

This configuration gets values from the AWS SSM parameter store. Encrypted values will be automatically decrypted.

Unique values across stages

SSM Parameter Store could do a lookup of value names prepending a "stage name" e.g. prod, staging, dev. This is use to be able to create parameters with unique names and reference them in the function using a consistent name. For example the value /database/username for the stage name prod will result in a lookup of the parameter /prod/database/username.

The environment name is set via the environment variable STAGE_NAME.

Installation

SSM Parameter store configuration must be installed using the userverless-ssm-config package:

libraryDependencies += "io.onema" %% "userverless-ssm-config" % "<LATEST_VERSION>"

To use the SSM environment variable in your function simply extend from the SsmLambdaConfiguration trait like such

class TestFunction(snsClientMock: AmazonSNSAsync) extends LambdaHandler with SsmLambdaConfiguration {
  val foo: Option[String] = getValue("/foo")
  val barHierarchy: Map[String, String] = getValues("/bar/")
}

NoopLambdaConfig

This trait always returns None for getValue and Seq() for getValues.

Custom implementations

You may create your own custom implementations by extending the LambdaConfiguration trait and implementing getValue and getValues.