Configuration File

Whenever you create a new project using chalice new-project, a .chalice directory is created for you. In this directory is a config.json file that you can use to control what happens when you chalice deploy:

$ tree -a
.
├── .chalice
│   └── config.json
├── app.py
└── requirements.txt

1 directory, 3 files

Stage Specific Configuration

As of version 0.7.0 of chalice, you can specify configuration that is specific to a chalice stage as well as configuration that should be shared across all stages. See the Chalice Stages doc for more information about chalice stages.

  • stages - This value of this key is a mapping of chalice stage name to stage configuration. Chalice assumes a default stage name of dev. If you run the chalice new-project command on chalice 0.7.0 or higher, this key along with the default dev key will automatically be created for you. See the examples section below for some stage specific configurations.

The following config values can either be specified per stage config or as a top level key which is not tied to a specific key. Whenever a stage specific configuration value is needed, the stages mapping is checked first. If no value is found then the top level keys will be checked.

  • api_gateway_stage - The name of the API gateway stage. This will also be the URL prefix for your API (https://endpoint/prefix/your-api).
  • manage_iam_role - true/false. Indicates if you want chalice to create and update the IAM role used for your application. By default, this value is true. However, if you have a pre-existing role you’ve created, you can set this value to false and a role will not be created or updated. "manage_iam_role": false means that you are responsible for managing the role and any associated policies associated with that role. If this value is false you must specify an iam_role_arn, otherwise an error is raised when you try to run chalice deploy.
  • iam_role_arn - If manage_iam_role is false, you must specify this value that indicates which IAM role arn to use when configuration your application. This value is only used if manage_iam_role is false.
  • autogen_policy - A boolean value that indicates if chalice should try to automatically generate an IAM policy based on analyzing your application source code. The default value is true. If this value is false then chalice will load try to a local file in .chalice/policy-<stage-name>.json instead of auto-generating a policy from source code analysis.
  • iam_policy_file - When autogen_policy is false, chalice will try to load an IAM policy from disk instead of auto-generating one based on source code analysis. The default location of this file is .chalice/policy-<stage-name>.json, e.g .chalice/policy-dev.json, .chalice/policy-prod.json, etc. You can change the filename by providing this iam_policy_file config option. This filename is relative to the .chalice directory.
  • environment_variables - A mapping of key value pairs. These key value pairs will be set as environment variables in your application. All environment variables must be strings. If this key is specified in both a stage specific config option as well as a top level key, the stage specific environment variables will be merged into the top level keys. See the examples section below for a concrete example.
  • lambda_timeout - An integer representing the function execution time, in seconds, at which AWS Lambda should terminate the function. The default lambda_timeout is 60 seconds.
  • lambda_memory_size - An integer representing the amount of memory, in MB, your Lambda function is given. AWS Lambda uses this memory size to infer the amount of CPU allocated to your function. The default lambda_memory_size value is 128. The value must be a multiple of 64 MB.
  • tags - A mapping of key value pairs. These key value pairs will be set as the tags on the resources running your deployed application. All tag keys and values must be strings. Similar to environment_variables, if a key is specified in both a stage specific config option as well as a top level key, the stage specific tags will be merged into the top level keys. By default, all chalice deployed resources are tagged with the key 'aws-chalice' whose value is 'version={chalice-version}:stage={stage-name}:app={app-name}'. Currently only the following chalice deployed resources are tagged: Lambda functions.
  • subnet_ids - A list of subnet ids for VPC configuration. This value can be provided per stage as well as per Lambda function. In order for this value to take effect, you must also provide the security_group_ids value. When both values are provided and autogen_policy is True, chalice will automatically update your IAM role with the necessary permissions to create, describe, and delete ENIs. If you are managing the IAM role policy yourself, make sure to update your permissions accordingly, as described in the AWS Lambda VPC documentation.
  • security_group_ids - A list of security groups for VPC configuration. This value can be provided per stage as well as per Lambda function. In order for this value to take effect, you must also provide the subnet_ids value.
  • reserved_concurrency - An integer representing each function’s reserved concurrency. This value can be provided per stage as well as per Lambda function. AWS Lambda reserves this value of concurrency to each lambda deployed in this stage. If the value is set to 0, invocations to this function are blocked. If the value is unset, there will be no reserved concurrency allocations. For more information, see AWS Documentation on managing concurrency.

Lambda Specific Configuration

In addition to a chalice stage, there are also some configuration values that can be specified per Lambda function. A chalice app can have many stages, and a stage can have many Lambda functions. To configure per lambda configuration, you add a lambda_functions key in your stage configuration:

{
  "version": "2.0",
  "app_name": "app",
  "stages": {
    "dev": {
      "lambda_functions": {
        "foo": {
          "lambda_timeout": 120
        }
      }
    }
  }
}

Each key in the lambda_functions dictionary is the name of a Lambda function in your app. The value is a dictionary of configuration that will be applied to that function. These are the configuration options that can be applied per function:

  • iam_policy_file
  • lambda_memory_size
  • lambda_timeout
  • iam_role_arn
  • manage_iam_role
  • autogen_policy
  • environment_variables
  • tags
  • subnet_ids
  • security_group_ids
  • reserved_concurrency

See the Stage Specific Configuration section above for a description of these config options.

Examples

Below are examples that show how you can configure your chalice app.

IAM Roles and Policies

Here’s an example for configuring IAM policies across stages:

{
  "version": "2.0",
  "app_name": "app",
  "stages": {
    "dev": {
      "autogen_policy": true,
      "api_gateway_stage": "dev"
    },
    "beta": {
      "autogen_policy": false,
      "iam_policy_file": "beta-app-policy.json"
    },
    "prod": {
      "manage_iam_role": false,
      "iam_role_arn": "arn:aws:iam::...:role/prod-role"
    }
  }
}

In this config file we’re specifying three stages, dev, beta, and prod. In the dev stage, chalice will automatically generate an IAM policy based on analyzing the application source code. For the beta stage, chalice will load the .chalice/beta-app-policy.json file and use it as the policy to associate with the IAM role for that stage. In the prod stage, chalice won’t modify any IAM roles. It will just set the IAM role for the Lambda function to be arn:aws:iam::...:role/prod-role.

Here’s an example that show config precedence:

{
  "version": "2.0",
  "app_name": "app",
  "api_gateway_stage": "api",
  "stages": {
    "dev": {
    },
    "beta": {
    },
    "prod": {
      "api_gateway_stage": "prod",
      "manage_iam_role": false,
      "iam_role_arn": "arn:aws:iam::...:role/prod-role"
    }
  }
}

In this config file, both the dev and beta stage will have an API gateway stage name of api because they will default to the top level api_gateway_stage key. However, the prod stage will have an API gateway stage name of prod because the api_gateway_stage is specified in {"stages": {"prod": ...}} mapping.

Environment Variables

In the following example, environment variables are specified both as top level keys as well as per stage. This allows us to provide environment variables that all stages should have as well as stage specific environment variables:

{
  "version": "2.0",
  "app_name": "app",
  "environment_variables": {
    "SHARED_CONFIG": "foo",
    "OTHER_CONFIG": "from-top"
  },
  "stages": {
    "dev": {
      "environment_variables": {
        "TABLE_NAME": "dev-table",
        "OTHER_CONFIG": "dev-value"
      }
    },
    "prod": {
      "environment_variables": {
        "TABLE_NAME": "prod-table",
        "OTHER_CONFIG": "prod-value"
      }
    }
  }
}

For the above config, the dev stage will have the following environment variables set:

{
  "SHARED_CONFIG": "foo",
  "TABLE_NAME": "dev-table",
  "OTHER_CONFIG": "dev-value",
}

The prod stage will have these environment variables set:

{
  "SHARED_CONFIG": "foo",
  "TABLE_NAME": "prod-table",
  "OTHER_CONFIG": "prod-value",
}

Per Lambda Examples

Suppose we had the following chalice app:

from chalice import Chalice

app = Chalice(app_name='demo')

@app.lambda_function()
def foo(event, context):
    pass

@app.lambda_function()
def bar(event, context):
    pass

Given these two functions, we’d like to configure the functions as follows:

  • Both functions should have an environment variable OWNER with value dev-team.
  • The foo function should have an autogenerated IAM policy managed by chalice.
  • The foo function should be run in a VPC with subnet ids sn-1 and sn-2, with security groups sg-10 and sg-11. Chalice should also automatically configure the IAM policy with permissions to modify EC2 network interfaces.
  • The bar function should use a pre-existing IAM role that was created outside of chalice. Chalice should not perform an IAM role management for the bar function.
  • The bar function should have an environment variable TABLE_NAME with value mytable.

We can accomplish all this with this config file:

{
  "stages": {
    "dev": {
      "environment_variables": {
        "OWNER": "dev-team"
      }
      "api_gateway_stage": "api",
      "lambda_functions": {
        "foo": {
          "subnet_ids": ["sn-1", "sn-2"],
          "security_group_ids": ["sg-10", "sg-11"],
        },
        "bar": {
          "manage_iam_role": false,
          "iam_role_arn": "arn:aws:iam::my-role-name",
          "environment_variables": {"TABLE_NAME": "mytable"}
        }
      }
    }
  },
  "version": "2.0",
  "app_name": "demo"
}