Chalice

class Chalice(app_name)

This class represents a chalice application. It provides:

  • The ability to register routes using the route() method.
  • Within a view function, the ability to introspect the current request using the current_request attribute which is an instance of the Request class.
app_name

The name of the Chalice app. This corresponds to the value provided when instantiating a Chalice object.

current_request

An object of type Request. This value is only set when a view function is being called. This attribute can be used to introspect the current HTTP request.

api

An object of type APIGateway. This attribute can be used to control how apigateway interprets Content-Type headers in both requests and responses.

lambda_context

A Lambda context object that is passed to the invoked view by AWS Lambda. You can find out more about this object by reading the lambda context object documentation.

Note

This is only set on @app.route handlers. For other handlers it will be None. Instead the event parameter will have a context property. For example S3Event.context.

debug

A boolean value that enables debugging. By default, this value is False. If debugging is true, then internal errors are returned back to the client. Additionally, debug log messages generated by the framework will show up in the cloudwatch logs. Example usage:

from chalice import Chalice

app = Chalice(app_name="appname")
app.debug = True
websocket_api

An object of type WebsocketAPI. This attribute can be used to send messages to websocket clients connected through API Gateway.

route(path, **options)

Register a view function for a particular URI path. This method is intended to be used as a decorator for a view function. For example:

from chalice import Chalice

app = Chalice(app_name="appname")

@app.route('/resource/{value}', methods=['PUT'])
def viewfunction(value):
    pass
Parameters:
  • path (str) – The path to associate with the view function. The path should only contain [a-zA-Z0-9._-] chars and curly braces for parts of the URL you would like to capture. The path should not end in a trailing slash, otherwise a validation error will be raised during deployment.
  • methods (list) – Optional parameter that indicates which HTTP methods this view function should accept. By default, only GET requests are supported. If you only wanted to support POST requests, you would specify methods=['POST']. If you support multiple HTTP methods in a single view function (methods=['GET', 'POST']), you can check the app.current_request.method attribute to see which HTTP method was used when making the request. You can provide any HTTP method supported by API Gateway, which includes: GET, POST, PUT, PATCH, HEAD, OPTIONS, and DELETE.
  • name (str) – Optional parameter to specify the name of the view function. You generally do not need to set this value. The name of the view function is used as the default value for the view name.
  • authorizer (Authorizer) – Specify an authorizer to use for this view. Can be an instance of CognitoUserPoolAuthorizer, CustomAuthorizer or IAMAuthorizer.
  • content_types (str) – A list of content types to accept for this view. By default application/json is accepted. If this value is specified, then chalice will reject any incoming request that does not match the provided list of content types with a 415 Unsupported Media Type response.
  • api_key_required (boolean) – Optional parameter to specify whether the method required a valid API key.
  • cors – Specify if CORS is supported for this view. This can either by a boolean value, None, or an instance of CORSConfig. Setting this value is set to True gives similar behavior to enabling CORS in the AWS Console. This includes injecting the Access-Control-Allow-Origin header to have a value of * as well as adding an OPTIONS method to support preflighting requests. If you would like more control over how CORS is configured, you can provide an instance of CORSConfig.
authorizer(name, **options)

Register a built-in authorizer.

from chalice import Chalice, AuthResponse

app = Chalice(app_name="appname")

@app.authorizer(ttl_seconds=30)
def my_auth(auth_request):
    # Validate auth_request.token, and then:
    return AuthResponse(routes=['/'], principal_id='username')

@app.route('/', authorizer=my_auth)
def viewfunction(value):
    pass
Parameters:
  • ttl_seconds – The number of seconds to cache this response. Subsequent requests that require this authorizer will use a cached response if available. The default is 300 seconds.
  • execution_role – An optional IAM role to specify when invoking the Lambda function associated with the built-in authorizer.
schedule(expression, name=None)

Register a scheduled event that’s invoked on a regular schedule. This will create a lambda function associated with the decorated function. It will also schedule the lambda function to be invoked with a scheduled CloudWatch Event.

See Scheduled Events for more information.

@app.schedule('cron(15 10 ? * 6L 2002-2005)')
def cron_handler(event):
    pass

@app.schedule('rate(5 minutes)')
def rate_handler(event):
    pass

@app.schedule(Rate(5, unit=Rate.MINUTES))
def rate_obj_handler(event):
    pass

@app.schedule(Cron(15, 10, '?', '*', '6L', '2002-2005'))
def cron_obj_handler(event):
    pass
Parameters:
  • expression – The schedule expression to use for the CloudWatch event rule. This value can either be a string value or an instance of type ScheduleExpression, which is either a Cron or Rate object. If a string value is provided, it will be provided directly as the ScheduleExpression value in the PutRule API call.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_cw_event(pattern, name=None)

Create a lambda function and configure it to be invoked whenever an event that matches the given pattern flows through CloudWatch Events or Event Bridge.

Parameters:
  • pattern – The event pattern to use to filter subscribed events. See the CloudWatch Events docs for examples https://amzn.to/2OlqZso
  • name – The name of the function to create. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_s3_event(bucket, events=None, prefix=None, suffix=None, name=None)

Create a lambda function and configure it to be automatically invoked whenever an event happens on an S3 bucket.

Warning

You can’t use the chalice package command when using the on_s3_event decorator. This is because CFN does not support configuring an existing S3 bucket.

See S3 Events for more information.

This example shows how you could implement an image resizer that’s triggered whenever an object is uploaded to the images/ prefix of an S3 bucket (e.g s3://mybucket/images/house.jpg).

@app.on_s3_event('mybucket', events=['s3:ObjectCreated:Put'],
                 prefix='images/', suffix='.jpg')
def resize_image(event):
    with tempfile.NamedTemporaryFile('w') as f:
        s3.download_file(event.bucket, event.key, f.name)
        resize_image(f.name)
        s3.upload_file(event.bucket, 'resized/%s' % event.key, f.name)
Parameters:
  • bucket – The name of the S3 bucket. This bucket must already exist.
  • events – A list of strings indicating the events that should trigger the lambda function. See Supported Event Types for the full list of strings you can provide. If this option is not provided, a default of ['s3:ObjectCreated:*'] is used, which will configure the lambda function to be invoked whenever a new object is created in the S3 bucket.
  • prefix – An optional key prefix. This specifies that the lambda function should only be invoked if the key starts with this prefix (e.g. prefix='images/'). Note that this value is not a glob (e.g. images/*), it is a literal string match for the start of the key.
  • suffix – An optional key suffix. This specifies that the lambda function should only be invoked if the key name ends with this suffix (e.g. suffix='.jpg'). Note that this value is not a glob (e.g. *.txt), it is a literal string match for the end of the key.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_sns_message(topic, name=None)

Create a lambda function and configure it to be automatically invoked whenever an SNS message is published to the specified topic.

See SNS Events for more information.

This example prints the subject and the contents of the message whenever something publishes to the sns topic of mytopic. In this example, the input parameter is of type SNSEvent.

app.debug = True

@app.on_sns_message(topic='mytopic')
def handler(event):
    app.log.info("SNS subject: %s", event.subject)
    app.log.info("SNS message: %s", event.message)
Parameters:
  • topic – The name or ARN of the SNS topic you want to subscribe to.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_sqs_message(queue, batch_size=1, name=None)

Create a lambda function and configure it to be automatically invoked whenever a message is published to the specified SQS queue.

The lambda function must accept a single parameter which is of type SQSEvent.

If the decorated function returns without raising any exceptions then Lambda will automatically delete the SQS messages associated with the SQSEvent. You don’t need to manually delete messages. If any exception is raised, Lambda won’t delete any messages, and the messages will become available once the visibility timeout has been reached. Note that for batch sizes of more than one, either the entire batch succeeds and all the messages in the batch are deleted by Lambda, or the entire batch fails. The default batch size is 1. See the Using AWS Lambda with Amazon SQS for more information on how Lambda integrates with SQS.

See the SQS Events topic guide for more information on using SQS in Chalice.

app.debug = True

@app.on_sqs_message(queue='myqueue')
def handler(event):
    app.log.info("Event: %s", event.to_dict())
    for record in event:
        app.log.info("Message body: %s", record.body)
Parameters:
  • queue – The name of the SQS queue you want to subscribe to. This is the name of the queue, not the ARN or Queue URL.
  • batch_size – The maximum number of messages to retrieve when polling for SQS messages. The event parameter can have multiple SQS messages associated with it. This is why the event parameter passed to the lambda function is iterable. The batch size controls how many messages can be in a single event.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_kinesis_record(stream, batch_size=100, starting_position='LATEST', name=None)

Create a lambda function and configure it to be automatically invoked whenever data is published to the specified Kinesis stream.

The lambda function must accept a single parameter which is of type KinesisEvent.

If the decorated function raises an exception, Lambda retries the batch until processing succeeds or the data expires.

See Using AWS Lambda with Amazon Kinesis for more information on how Lambda integrates with Kinesis.

app.debug = True

@app.on_kinesis_record(stream='mystream')
def handler(event):
    app.log.info("Event: %s", event.to_dict())
    for record in event:
        app.log.info("Message body: %s", record.data)
Parameters:
  • stream – The name of the Kinesis stream you want to subscribe to. This is the name of the data stream, not the ARN.
  • batch_size – The maximum number of messages to retrieve when polling for Kinesis messages. The event parameter can have multiple Kinesis records associated with it. This is why the event parameter passed to the lambda function is iterable. The batch size controls how many messages can be in a single event.
  • starting_position

    Specifies where to start processing records. This can have the following values:

    • LATEST - Process new records that are added to the stream.
    • TRIM_HORIZON - Process all records in the stream.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
on_dynamodb_record(stream_arn, batch_size=100, starting_position='LATEST', name=None)

Create a lambda function and configure it to be automatically invoked whenever data is written to a DynamoDB stream.

The lambda function must accept a single parameter which is of type DynamoDBEvent.

If the decorated function raises an exception, Lambda retries the batch until processing succeeds or the data expires.

See Using AWS Lambda with Amazon DynamoDB for more information on how Lambda integrates with DynamoDB Streams.

app.debug = True

@app.on_dynamodb_record(stream_arn='arn:aws:dynamodb:...:stream')
def handler(event):
    app.log.info("Event: %s", event.to_dict())
    for record in event:
        app.log.info("New: %s", record.new_image)
Parameters:
  • stream_arn – The name of the DynamoDB stream ARN you want to subscribe to. Note that, unlike other event handlers that accept the resource name, you must provide the stream ARN when subscribing to the DynamoDB stream ARN.
  • batch_size – The maximum number of messages to retrieve when polling for DynamoDB messages. The event parameter can have multiple DynamoDB records associated with it. This is why the event parameter passed to the lambda function is iterable. The batch size controls how many messages can be in a single event.
  • starting_position

    Specifies where to start processing records. This can have the following values:

    • LATEST - Process new records that are added to the stream.
    • TRIM_HORIZON - Process all records in the stream.
  • name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
lambda_function(name=None)

Create a pure lambda function that’s not connected to anything.

See Pure Lambda Functions for more information.

Parameters:name – The name of the function to use. This name is combined with the chalice app name as well as the stage name to create the entire lambda function name. This parameter is optional. If it is not provided, the name of the python function will be used.
register_blueprint(blueprint, name_prefix=None, url_prefix=None)

Register a Blueprint to a Chalice app. See Blueprints for more information.

Parameters:
  • blueprint – The Blueprint to register to the app.
  • name_prefix – An optional name prefix that’s added to all the resources specified in the blueprint.
  • url_prefix – An optional url prefix that’s added to all the routes defined the Blueprint. This allows you to set the root mount point for all URLs in a Blueprint.
on_ws_connect(event)

Create a Websocket API connect event handler.

Parameters:event – The WebsocketEvent received to indicate a new connection has been registered with API Gateway. The identifier of this connection is under the WebsocketEvent.connection_id attribute.

see Websockets for more information.

on_ws_message(event)

Create a Websocket API message event handler.

Parameters:event – The WebsocketEvent received to indicate API Gateway received a message from a connected client. The identifier of the client that sent the message is under the WebsocketEvent.connection_id attribute. The content of the message is available in the WebsocketEvent.body attribute.

see Websockets for more information.

on_ws_disconnect(event)

Create a Websocket API disconnect event handler.

Parameters:event – The WebsocketEvent received to indicate an existing connection has been disconnected from API Gateway. The identifier of this connection is under the WebsocketEvent.connection_id attribute.

see Websockets for more information.

middleware(event_type='all')

Register a middleware with a Chalice application. This decorator will register a function as Chalice middleware, which will be automatically invoked as part of the request/response cycle for a Lambda invocation. You can provide the event_type argument to indicate what type of lambda events you want to register with. The default value, all, indicates that the middleware will be called for all Lambda functions defined in your Chalice app. Supported values are:

The decorated function must accept two arguments, event and get_response. The event is the input event associated with the Lambda invocation, and get_response is a callable that takes an input event and will invoke the next middleware in the chain, and eventually the original Lambda handler. Below is a noop middleware that shows the minimum needed to write middleware:

@app.middleware('all')
def mymiddleware(event, get_response):
    return get_response(event)

See Middleware for more information on writing middleware.

register_middleware(func, event_type='all')

Register a middleware with a Chalice application. This is the same behavior as the Chalice.middleware() decorator and is useful if you want to register middleware for pre-existing functions:

import thirdparty

app.register_middleware(thirdparty.func, 'all')
class ConvertToMiddleware(lambda_wrapper)

This class is used to convert a function that wraps/proxies a Lambda function into middleware. This allows this wrapper to automatically be applied to every function in your app. For example, if you had the following logging decorator:

def log_invocation(func):
    def wrapper(event, context):
        logger.debug("Before lambda function.")
        response = func(event, context)
        logger.debug("After lambda function.")
    return wrapper

@app.lambda_function()
@log_invocation
def myfunction(event, context):
    logger.debug("In myfunction().")

Rather than decorate every Lambda function with the @log_invocation decorator, you can instead use ConvertToMiddleware to automatically apply this wrapper to every Lambda function in your app.

app.register_middleware(ConvertToMiddleware(log_invoation))

Request

class Request

A class that represents the current request. This is mapped to the app.current_request object.

@app.route('/objects/{key}', methods=['GET', 'PUT'])
def myobject(key):
    request = app.current_request  # type: Request
    if request.method == 'PUT':
        # handle PUT request
        pass
    elif request.method == 'GET':
        # handle GET request
        pass
path

The path of the HTTP request.

query_params

A MultiDict of the query params for the request. This value is None if no query params were provided in the request. The MultiDict acts like a normal dictionary except that you can call the method getlist() to get multiple keys from the same query string parameter

request = app.current_request
# Raises an exception if key doesn't exist, usual Python behavior.
single_param = request.query_params['single']

# None if key doesn't exist, usual Python behavior
another_param = request.query_params.get('another_param')

# A List of all parameters named multi_param, Throws an exception if
# key doesn't exist
multi_param_list = request.query_params.getlist('multi_param')
headers

A dict of the request headers.

uri_params

A dict of the captured URI params. This value is None if no URI params were provided in the request.

method

The HTTP method as a string.

json_body

The parsed JSON body (json.loads(raw_body)). This value will only be non-None if the Content-Type header is application/json, which is the default content type value in chalice.

raw_body

The raw HTTP body as bytes. This is useful if you need to calculate a checksum of the HTTP body.

context

A dict of additional context information.

stage_vars
A dict of configuration for the API Gateway stage.
lambda_context

A Lambda context object that is passed to the invoked view by AWS Lambda. You can find out more about this object by reading the lambda context object documentation.

to_dict()

Convert the Request object to a dictionary. This is useful for debugging purposes. This dictionary is guaranteed to be JSON serializable so you can return this value from a chalice view.

Response

class Response(body, headers=None, status_code=200)

A class that represents the response for the view function. You can optionally return an instance of this class from a view function if you want complete control over the returned HTTP response.

from chalice import Chalice, Response

app = Chalice(app_name='custom-response')


@app.route('/')
def index():
    return Response(body='hello world!',
                    status_code=200,
                    headers={'Content-Type': 'text/plain'})

New in version 0.6.0.

body

The HTTP response body to send back. This value must be a string.

headers

An optional dictionary of HTTP headers to send back. This is a dictionary of header name to header value, e.g {'Content-Type': 'text/plain'}

status_code

The integer HTTP status code to send back in the HTTP response.

Authorization

Each of these classes below can be provided using the authorizer argument for an @app.route(authorizer=...) call:

authorizer = CognitoUserPoolAuthorizer(
    'MyPool', header='Authorization',
    provider_arns=['arn:aws:cognito:...:userpool/name'])

@app.route('/user-pools', methods=['GET'], authorizer=authorizer)
def authenticated():
    return {"secure": True}
class CognitoUserPoolAuthorizer(name, provider_arns, header='Authorization')

New in version 0.8.1.

name

The name of the authorizer.

provider_arns

The Cognito User Pool arns to use.

header

The header where the auth token will be specified.

class IAMAuthorizer

New in version 0.8.3.

class CustomAuthorizer(name, authorizer_uri, ttl_seconds, header='Authorization')

New in version 0.8.1.

name

The name of the authorizer.

authorizer_uri

The URI of the lambda function to use for the custom authorizer. This usually has the form arn:aws:apigateway:{region}:lambda:path/2015-03-31/functions/{lambda_arn}/invocations.

ttl_seconds

The number of seconds to cache the returned policy from a custom authorizer.

header

The header where the auth token will be specified.

Built-in Authorizers

These classes are used when defining built-in authorizers in Chalice.

class AuthRequest(auth_type, token, method_arn)

An instance of this class is passed as the first argument to an authorizer defined via @app.authorizer(). You generally do not instantiate this class directly.

auth_type

The type of authentication

token

The authorization token. This is usually the value of the Authorization header.

method_arn

The ARN of the API gateway being authorized.

class AuthResponse(routes, principal_id, context=None)
routes

A list of authorized routes. Each element in the list can either by a string route such as “/foo/bar” or an instance of AuthRoute. If you specify the URL as a string, then all supported HTTP methods will be authorized. If you want to specify which HTTP methods are allowed, you can use AuthRoute. If you want to specify that all routes and HTTP methods are supported you can use the wildcard value of "*": AuthResponse(routes=['*'], ...)

principal_id

The principal id of the user.

context

An optional dictionary of key value pairs. This dictionary will be accessible in the app.current_request.context in all subsequent authorized requests for this user.

class AuthRoute(path, methods)

This class be used in the routes attribute of a AuthResponse instance to get fine grained control over which HTTP methods are allowed for a given route.

path

The allowed route specified as a string

methods

A list of allowed HTTP methods.

APIGateway

class APIGateway

This class is used to control how API Gateway interprets Content-Type headers in both requests and responses.

There is a single instance of this class attached to each Chalice object under the api attribute.

cors

Global cors configuration. If a route-level cors configuration is not provided, or is None then this configuration will be used. By default it is set to False. This can either be True, False, or an instance of the CORSConfig class. This makes it easy to enable CORS for your entire application by setting app.api.cors = True.

New in version 1.12.1.

default_binary_types

The value of default_binary_types are the Content-Types that are considered binary by default. This value should not be changed, instead you should modify the binary_types list to change the behavior of a content type. Its value is: application/octet-stream, application/x-tar, application/zip, audio/basic, audio/ogg, audio/mp4, audio/mpeg, audio/wav, audio/webm, image/png, image/jpg, image/jpeg, image/gif, video/ogg, video/mpeg, video/webm.

binary_types

The value of binary_types controls how API Gateway interprets requests and responses as detailed below.

If an incoming request has a Content-Type header value that is present in the binary_types list it will be assumed that its body is a sequence of raw bytes. You can access these bytes by accessing the app.current_request.raw_body property.

If an outgoing response from Chalice has a header Content-Type that matches one of the binary_types its body must be a bytes type object. It is important to note that originating request must have the Accept header for the same type as the Content-Type on the response. Otherwise a 400 error will be returned.

This value can be modified to change what types API Gateway treats as binary. The easiest way to do this is to simply append new types to the list.

app.api.binary_types.append('application/my-binary-data')

Keep in mind that there can only be a total of 25 binary types at a time and Chalice by default has a list of 16 types. It is recommended if you are going to make extensive use of binary types to reset the list to the exact set of content types you will be using. This can easily be done by reassigning the whole list.

app.api.binary_types = [
    'application/octet-stream',
    'application/my-binary-data',
]

Implementation Note: API Gateway and Lambda communicate through a JSON event which is encoded using UTF-8. The raw bytes are temporarily encoded using base64 when being passed between API Gateway and Lambda. In the worst case this encoding can cause the binary body to be inflated up to 4/3 its original size. Lambda only accepts an event up to 6mb, which means even if your binary data was not quite at that limit, with the base64 encoding it may exceed that limit. This will manifest as a 502 Bad Gateway error.

WebsocketAPI

class WebsocketAPI

This class is used to send messages to websocket clients connected to an API Gateway Websocket API.

session

A boto3 Session that will be used to send websocket messages to clients. Any custom configuration can be set through a botocore session. This must be manually set before websocket features can be used.

import botocore
from boto3.session import Session
from chalice import Chalice

app = Chalice('example')
session = botocore.session.Session()
session.set_config_variable('retries', {'max_attempts': 0})
app.websocket_api.session = Session(botocore_session=session)
configure(domain_name, stage)

Configure prepares the WebsocketAPI to call the send() method. Without first calling this method calls to send() will fail with the message WebsocketAPI needs to be configured before sending messages.. This is because a boto3 apigatewaymanagementapi client must be created from the session with a custom endpoint in order to properly communicate with our API Gateway WebsocketAPI. This method is called on your behalf before each of the websocket handlers: on_ws_connect, on_ws_message, on_ws_disconnect. This ensures that the send() method is available in each of those handlers.

send(connection_id, message)

requires boto3>=1.9.91

Method to send a message to a client. The connection_id is the unique identifier of the socket to send the message to. The message must be a utf-8 string.

If the socket is disconnected it raises a WebsocketDisconnectedError error.

close(connection_id)

requires boto3>=1.9.221

Method to close a WebSocket connection. The connection_id is the unique identifier of the socket to close.

If the socket is already disconnected it raises a WebsocketDisconnectedError error.

info(connection_id)

requires boto3>=1.9.221

Method to get info about a WebSocket. The connection_id is the unique identifier of the socket to get info about.

The following is an example of the format this method returns:

{
    'ConnectedAt': datetime(2015, 1, 1),
    'Identity': {
        'SourceIp': 'string',
        'UserAgent': 'string'
    },
    'LastActiveAt': datetime(2015, 1, 1)
}

If the socket is disconnected it raises a WebsocketDisconnectedError error.

class WebsocketDisconnectedError

An exception raised when a message is sent to a websocket that has disconnected.

connection_id

The unique identifier of the websocket that was disconnected.

CORS

class CORSConfig(allow_origin='*', allow_headers=None, expose_headers=None, max_age=None, allow_credentials=None)

CORS configuration to attach to a route, or globally on app.api.cors.

from chalice import CORSConfig
cors_config = CORSConfig(
    allow_origin='https://foo.example.com',
    allow_headers=['X-Special-Header'],
    max_age=600,
    expose_headers=['X-Special-Header'],
    allow_credentials=True
)

@app.route('/custom_cors', methods=['GET'], cors=cors_config)
def supports_custom_cors():
    return {'cors': True}

New in version 0.8.1.

allow_origin

The value of the Access-Control-Allow-Origin to send in the response. Keep in mind that even though the Access-Control-Allow-Origin header can be set to a string that is a space separated list of origins, this behavior does not work on all clients that implement CORS. You should only supply a single origin to the CORSConfig object. If you need to supply multiple origins you will need to define a custom handler for it that accepts OPTIONS requests and matches the Origin header against a whitelist of origins. If the match is successful then return just their Origin back to them in the Access-Control-Allow-Origin header.

allow_headers

The list of additional allowed headers. This list is added to list of built in allowed headers: Content-Type, X-Amz-Date, Authorization, X-Api-Key, X-Amz-Security-Token.

expose_headers

A list of values to return for the Access-Control-Expose-Headers:

max_age

The value for the Access-Control-Max-Age

allow_credentials

A boolean value that sets the value of Access-Control-Allow-Credentials.

Event Sources

New in version 1.0.0b1.

class Rate(value, unit)

An instance of this class can be used as the expression value in the Chalice.schedule() method:

@app.schedule(Rate(5, unit=Rate.MINUTES))
def handler(event):
    pass

Examples:

# Run every minute.
Rate(1, unit=Rate.MINUTES)

# Run every 2 hours.
Rate(2, unit=Rate.HOURS)
value

An integer value that presents the amount of time to wait between invocations of the scheduled event.

unit

The unit of the provided value attribute. This can be either Rate.MINUTES, Rate.HOURS, or Rate.DAYS.

MINUTES, HOURS, DAYS

These values should be used for the unit attribute.

class Cron(minutes, hours, day_of_month, month, day_of_week, year)

An instance of this class can be used as the expression value in the Chalice.schedule() method.

@app.schedule(Cron(15, 10, '?', '*', '6L', '2002-2005'))
def handler(event):
    pass

It provides more capabilities than the Rate class. There are a few limits:

  • You can’t specify day_of_month and day_of_week fields in the same Cron expression. If you specify a value in one of the fields, you must use a ? in the other.
  • Cron expressions that lead to rates faster than 1 minute are not supported.

For more information, see the API docs page.

Examples:

# Run at 10:00am (UTC) every day.
Cron(0, 10, '*', '*', '?', '*')

# Run at 12:15pm (UTC) every day.
Cron(15, 12, '*', '*', '?', '*')

# Run at 06:00pm (UTC) every Monday through Friday.
Cron(0, 18, '?', '*', 'MON-FRI', '*')

# Run at 08:00am (UTC) every 1st day of the month.
Cron(0, 8, 1, '*', '?', '*')

# Run every 15 minutes.
Cron('0/15', '*', '*', '*', '?', '*')

# Run every 10 minutes Monday through Friday.
Cron('0/10', '*', '?', '*', 'MON-FRI', '*')

# Run every 5 minutes Monday through Friday between
# 08:00am and 5:55pm (UTC).
Cron('0/5', '8-17', '?', '*', 'MON-FRI', '*')
class CloudWatchEvent

This is the input argument for a scheduled or CloudWatch events.

@app.schedule('rate(1 hour)')
def every_hour(event: CloudWatchEvent):
    pass

In the code example above, the event argument is of type CloudWatchEvent, which will have the following attributes.

version

By default, this is set to 0 (zero) in all events.

account

The 12-digit number identifying an AWS account.

region

Identifies the AWS region where the event originated.

detail

For CloudWatch events this will be the event payload. For scheduled events, this will be an empty dictionary.

detail_type

For scheduled events, this value will be "Scheduled Event".

source

Identifies the service that sourced the event. All events sourced from within AWS will begin with “aws.” Customer-generated events can have any value here as long as it doesn’t begin with “aws.” We recommend the use of java package-name style reverse domain-name strings.

For scheduled events, this will be aws.events.

time

The event timestamp, which can be specified by the service originating the event. If the event spans a time interval, the service might choose to report the start time, so this value can be noticeably before the time the event is actually received.

event_id

A unique value is generated for every event. This can be helpful in tracing events as they move through rules to targets, and are processed.

resources

This JSON array contains ARNs that identify resources that are involved in the event. Inclusion of these ARNs is at the discretion of the service.

For scheduled events, this will include the ARN of the CloudWatch rule that triggered this event.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the CloudWatchEvent object. Example:

{'account': '123457940291',
 'detail': {},
 'detail-type': 'Scheduled Event',
 'id': '12345678-b9f1-4667-9c5e-39f98e9a6113',
 'region': 'us-west-2',
 'resources': ['arn:aws:events:us-west-2:123457940291:rule/testevents-dev-every_minute'],
 'source': 'aws.events',
 'time': '2017-06-30T23:28:38Z',
 'version': '0'}
class S3Event

This is the input argument for an S3 event.

@app.on_s3_event(bucket='mybucket')
def event_handler(event: S3Event):
    app.log.info("Event received for bucket: %s, key %s",
                 event.bucket, event.key)

In the code example above, the event argument is of type S3Event, which will have the following attributes.

bucket

The S3 bucket associated with the event.

key

The S3 key name associated with the event. The original key name in the S3 event payload is URL encoded. However, this key attribute automatically URL decodes the key name for you. If you need access to the original URL encoded key name, you can access it through the to_dict() method.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the S3Event object. Note that this event is not modified in any way. This means that the key name of the S3 object is URL encoded, which is the way that S3 sends this value to Lambda.

class SNSEvent

This is the input argument for an SNS event handler.

@app.on_sns_message(topic='mytopic')
def event_handler(event: SNSEvent):
    app.log.info("Message received with subject: %s, message: %s",
                 event.subject, event.message)

In the code example above, the event argument is of type SNSEvent, which will have the following attributes.

subject

The subject of the SNS message that was published.

message

The string value of the SNS message that was published.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the SNSEvent object.

class SQSEvent

This is the input argument for an SQS event handler.

@app.on_sqs_message(queue='myqueue')
def event_handler(event: SQSEvent):
    app.log.info("Event: %s", event.to_dict())

In the code example above, the event argument is of type SQSEvent. An SQSEvent can have multiple sqs messages associated with it. To access the multiple messages, you can iterate over the SQSEvent.

__iter__()

Iterate over individual SQS messages associated with the event. Each element in the iterable is of type SQSRecord.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the SQSEvent object.

class SQSRecord

Represents a single SQS record within an SQSEvent.

body

The body of the SQS message.

receipt_handle

The receipt handle associated with the message. This is useful if you need to manually delete an SQS message to account for partial failures.

context

A Lambda context object that is passed to the handler by AWS Lambda.

to_dict()

Return the original dictionary associated with the given message. This is useful if you need direct access to the lambda event.

class KinesisEvent

This is the input argument for a Kinesis data stream event handler.

@app.on_kinesis_record(stream='mystream')
def event_handler(event: KinesisEvent):
    app.log.info("Event: %s", event.to_dict())

In the code example above, the event argument is of type KinesisEvent. A KinesisEvent can have multiple messages associated with it. To access the multiple messages, you can iterate over the KinesisEvent.

__iter__()

Iterate over individual Kinesis records associated with the event. Each element in the iterable is of type KinesisRecord.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the SQSEvent object.

class KinesisRecord

Represents a single Kinesis record within a KinesisEvent.

data

The payload data for the Kinesis record. This data is automatically base64 decoded for you and will be a bytes type.

sequence_number

The unique identifier of the record within its shard.

partition_key

Identifies which shard in the stream the data record is assigned to.

schema_version

Schema version for the record.

timestamp

The approximate time that the record was inserted into the stream. This is automatically converted to a datetime.datetime object.

context

A Lambda context object that is passed to the handler by AWS Lambda.

to_dict()

Return the original dictionary associated with the given message. This is useful if you need direct access to the lambda event.

class DynamoDBEvent

This is the input argument for a DynamoDB stream event handler.

@app.on_dynamodb_record(stream_arn='arn:aws:us-west-2:.../stream')
def event_handler(event: DynamoDBEvent):
    app.log.info("Event: %s", event.to_dict())
    for record in event:
        app.log.info(record.to_dict())

In the code example above, the event argument is of type DynamoDBEvent. A DynamoDBEvent can have multiple messages associated with it. To access the multiple messages, you can iterate over the DynamoDBEvent.

__iter__()

Iterate over individual DynamoDB records associated with the event. Each element in the iterable is of type DynamoDBRecord.

context

A Lambda context object that is passed to the handler by AWS Lambda. This is useful if you need the AWS request ID for tracing, or any other data in the context object.

to_dict()

Return the original event dictionary provided from Lambda. This is useful if you need direct access to the lambda event, for example if a new key is added to the lambda event that has not been mapped as an attribute to the SQSEvent object.

class DynamoDBRecord

Represents a single DynamoDB record within a DynamoDBEvent.

timestamp

The approximate time that the record was the stream record was created. This is automatically converted to a datetime.datetime object.

keys

The primary key attribute(s) for the DynamoDB item that was modified.

new_image

The item in the DynamoDB table as it appeared after it was modified.

old_image

The item in the DynamoDB table as it appeared before it was modified.

sequence_number

The sequence number of the stream record.

size_bytes

The size of the stream record, in bytes.

stream_view_type

The type of data from the modified DynamoDB item.

aws_region

The region associated with the event.

event_id

A unique identifier for the event.

event_name

The type of data modification that was performed on the DynamoDB table. This can be: INSERT, MODIFY, or DELETE.

event_source_arn

The ARN of the DynamoDB stream.

table_name

The name of the DynamoDB table associated with the stream. This value is computed from the event_source_arn parameter and will be an empty string if Chalice is unable to parse the table name from the event source ARN.

context

A Lambda context object that is passed to the handler by AWS Lambda.

to_dict()

Return the original dictionary associated with the given message. This is useful if you need direct access to the lambda event.

class LambdaFunctionEvent

This is the input argument of middleware registered to a pure Lambda function (@app.lambda_function()).

event

The original input event dictionary.

context

A Lambda context object that is passed to the handler by AWS Lambda.

Blueprints

class Blueprint(import_name)

An object used for grouping related handlers together. This is primarily used as a mechanism for organizing your lambda handlers. Any decorator methods defined in the Chalice object are also defined on a Blueprint object. You can register a blueprint to a Chalice app using the Chalice.register_blueprint() method.

The import_name is the module in which the Blueprint is defined. It is used to construct the appropriate handler string when creating the Lambda functions associated with a Blueprint. This is typically the __name__ attribute:mybp = Blueprint(__name__).

See Blueprints for more information.

# In ./app.py

from chalice import Chalice
from chalicelib import myblueprint

app = Chalice(app_name='blueprints')
app.register_blueprint(myblueprint)

# In chalicelib/myblueprint.py

from chalice import Blueprint

myblueprint = Blueprint(__name__)

@myblueprint.route('/')
def index():
    return {'hello': 'world'}

Websockets

class WebsocketEvent

Event object event that is passed as the sole arugment to any handler function decorated with one of the three websocket related handlers: on_ws_connect, on_ws_disconnect, on_ws_message.

domain_name

The domain name of the endpoint for the API Gateway Websocket API.

stage

The API Gateway stage of the Websocket API.

connection_id

A handle that uniquely identifies a connection with API Gateway.

body

The message body received. This is only populated on the on_ws_message otherwise it will be set to None.

json_body

The parsed JSON body (json.loads(body)) of the message. If the body is not JSON parsable then using this attribute will raise a ValueError.

See Websockets for more information.

Testing

class Client(app, stage_name='dev', project_dir='.')

A test client used to write tests for Chalice apps. It allows you to test Lambda function invocation as well as REST APIs. Depending on what you want to test, you’ll access the various attributes of this class. You can use this class as a context manager. When entering the context manager, any environment variables specified for your function will be set. The original environment variables are put back when the block is exited:

from chalice.test import Client

with Client(app) as client:
    result = client.http.post("/my-data")

See the Testing documentation for more details on testing your Chalice app.

lambda_

Returns the Lambda test client TestLambdaClient.

http

Returns the test client for REST APIs TestHTTPClient.

events

Returns the test client for generating Lambda events TestEventsClient.

class TestLambdaClient(import_name)

Test client for invoking Lambda functions. This class should not be instantiated directly, and instead should be accessed via the Client.lambda_ attribute:

@app.lambda_function()
def myfunction(event, context):
    return {"hello": "world"}

with Client(app) as client:
    result = client.lambda_.invoke("myfunction")
    assert result.payload == {"hello": "world"}
invoke(function_name, payload=None)

Invoke a Lambda function by name. The name should match the resource name of the function. This is typically the name of the python function unless an explicit name= kwarg is provided when registering the function.

Returns an InvokeResponse instance.

class TestHTTPClient(import_name)

Test client for REST APIs. This class should not be instantiated directly, and instead should be accessed via the Client.http attribute:

with Client(app) as client:
    response = client.http.get("/my-route")
request(method, path, headers=None, body=b'')

Makes a test HTTP request to your REST API. Returns an HTTPResponse. You can also use the methods below to make a request with a specific HTTP method instead of using this method directly, e.g. client.http.get("/foo") instead of client.http.request("GET", "/foo").

get(path, **kwargs)

Makes an HTTP GET request.

post(path, **kwargs)

Makes an HTTP POST request.

put(path, **kwargs)

Makes an HTTP PUT request.

patch(path, **kwargs)

Makes an HTTP PATCH request.

options(path, **kwargs)

Makes an HTTP OPTIONS request.

delete(path, **kwargs)

Makes an HTTP DELETE request.

head(path, **kwargs)

Makes an HTTP HEAD request.

class TestEventsClient(import_name)

Test client for generating Lambda events. This class should not be instantiated directly, and instead should be accessed via the Client.events attribute:

with Client(app) as client:
    result = client.lambda_.invoke(
        "my_sns_handler",
        client.events.generate_sns_event("Hello world")
    )
generate_sns_event(message, subject='')

Generates a sample SNS event.

generate_s3_event(message, subject='')

Generates a sample S3 event.

generate_sqs_event(message, subject='')

Generates a sample SQS event.

generate_cw_event(message, subject='')

Generates a sample CloudWatch event.

class HTTPResponse
body

The body of the HTTP response, in bytes.

headers

A dictionary of HTTP headers in the resopnse.

status_code

The status code of the HTTP response.

class InvokeResponse(payload)
payload

The response payload of Lambda invocation.

Sample Applications →