Metadata-Version: 2.1
Name: domovoi
Version: 2.0.1
Summary: AWS Lambda event handler manager
Home-page: https://github.com/kislyuk/domovoi
Author: Andrey Kislyuk
Author-email: kislyuk@gmail.com
License: Apache Software License
Platform: MacOS X
Platform: Posix
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: MacOS :: MacOS X
Classifier: Operating System :: POSIX
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.3
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Requires-Dist: boto3 (<2,>=1.7.19)
Requires-Dist: chalice (<2,>=1.3.0)
Requires-Dist: enum34 (<2,>=1.1.6) ; python_version == "2.7"

Domovoi: AWS Lambda event handler manager
=========================================

*Domovoi* is an extension to `AWS Chalice <https://github.com/awslabs/chalice>`_ to handle `AWS Lambda
<https://aws.amazon.com/lambda/>`_ `event sources
<http://docs.aws.amazon.com/lambda/latest/dg/invoking-lambda-function.html#intro-core-components-event-sources>`_ other
than HTTP requests through API Gateway. Domovoi lets you easily configure and deploy a Lambda function to serve HTTP
requests through `ALB <https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html>`_,
on a schedule, or in response to a variety of events like an `SNS <https://aws.amazon.com/sns/>`_
or `SQS <https://aws.amazon.com/sqs/>`_ message, S3 event, or custom
`state machine <https://aws.amazon.com/step-functions/>`_ transition:

.. code-block:: python

    import json, boto3, domovoi

    app = domovoi.Domovoi()

    @app.alb_target()
    def serve(event, context):
        return dict(statusCode=200,
                    statusDescription="200 OK",
                    isBase64Encoded=False,
                    headers={"Content-Type": "application/json"},
                    body=json.dumps({"hello": "world"}))

    @app.scheduled_function("cron(0 18 ? * MON-FRI *)")
    def foo(event, context):
        context.log("foo invoked at 06:00pm (UTC) every Mon-Fri")
        return dict(result=True)

    @app.scheduled_function("rate(1 minute)")
    def bar(event, context):
        context.log("bar invoked once a minute")
        boto3.resource("sns").create_topic(Name="bartender").publish(Message=json.dumps({"beer": 1}))
        return dict(result="Work work work")

    @app.sns_topic_subscriber("bartender")
    def tend(event, context):
        message = json.loads(event["Records"][0]["Sns"]["Message"])
        context.log(dict(beer="Quadrupel", quantity=message["beer"]))

    # SQS messages are deleted upon successful exit, requeued otherwise.
    # See https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html
    @app.sqs_queue_subscriber("my_queue", batch_size=64)
    def process_queue_messages(event, context):
        message = json.loads(event["Records"][0]["body"])
        message_attributes = event["Records"][0]["messageAttributes"]
        # You can colocate a state machine definition with an SQS handler to launch a SFN driven lambda from SQS.
        return app.state_machine.start_execution(**message)["executionArn"]

    @app.cloudwatch_event_handler(source=["aws.ecs"])
    def monitor_ecs_events(event, context):
        message = json.loads(event["Records"][0]["Sns"]["Message"])
        context.log("Got an event from ECS: {}".format(message))

    @app.s3_event_handler(bucket="myS3bucket", events=["s3:ObjectCreated:*"], prefix="foo", suffix=".bar")
    def monitor_s3(event, context):
        context.log("Got an event from S3: {}".format(event))

    # Set use_sns=False, use_sqs=False to subscribe your Lambda directly to S3 events without forwarding them through an SNS-SQS bridge.
    # That approach has fewer moving parts, but you can only subscribe one Lambda function to events in a given S3 bucket.
    @app.s3_event_handler(bucket="myS3bucket", events=["s3:ObjectCreated:*"], prefix="foo", suffix=".bar", use_sns=False, use_sqs=False)
    def monitor_s3(event, context):
        context.log("Got an event from S3: {}".format(event))

    # DynamoDB event format: https://docs.aws.amazon.com/lambda/latest/dg/with-ddb.html
    @app.dynamodb_stream_handler(table_name="MyDynamoTable", batch_size=200)
    def handle_dynamodb_stream(event, context):
        context.log("Got {} events from DynamoDB".format(len(event["Records"])))
        context.log("First event: {}".format(event["Records"][0]["dynamodb"]))

    # Use the following command to log a CloudWatch Logs message that will trigger this handler:
    # python -c'import watchtower as w, logging as l; L=l.getLogger(); L.addHandler(w.CloudWatchLogHandler()); L.error(dict(x=8))'
    # See http://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/FilterAndPatternSyntax.html for the filter pattern syntax
    @app.cloudwatch_logs_sub_filter_handler(log_group_name="watchtower", filter_pattern="{$.x = 8}")
    def monitor_cloudwatch_logs(event, context):
        print("Got a CWL subscription filter event:", event)

    # See http://docs.aws.amazon.com/step-functions/latest/dg/concepts-amazon-states-language.html
    # See the "AWS Step Functions state machines" section below for a complete example of setting up a state machine.
    @app.step_function_task(state_name="Worker", state_machine_definition=state_machine)
    def worker(event, context):
        return {"result": event["input"] + 1, "my_state": context.stepfunctions_task_name}

Installation
------------
::

    pip install domovoi

Usage
-----
First-time setup::

    domovoi new-project

* Edit the Domovoi app entry point in ``app.py`` using examples above.
* Edit the IAM policy for your Lambda function in ``my_project/.chalice/policy-dev.json`` to add any permissions it
  needs.
* Deploy the event handlers::

    domovoi deploy

To stage files into the deployment package, use a ``domovoilib`` directory in your project where you would use
``chalicelib`` in Chalice. For example, ``my_project/domovoilib/rds_cert.pem`` becomes ``/var/task/domovoilib/rds_cert.pem``
with your function executing in ``/var/task/app.py`` with ``/var/task`` as the working directory. See the
`Chalice docs <http://chalice.readthedocs.io/>`_ for more information on how to set up Chalice configuration.

Supported event types
~~~~~~~~~~~~~~~~~~~~~
See `Supported Event Sources <http://docs.aws.amazon.com/lambda/latest/dg/invoking-lambda-function.html>`_ for an
overview of event sources that can be used to trigger Lambda functions. Domovoi supports the following event sources:

* `ALB HTTPS requests <https://docs.aws.amazon.com/lambda/latest/dg/lambda-services.html>`_
* `SNS subscriptions <https://docs.aws.amazon.com/lambda/latest/dg/with-sns.html>`_
* `SQS queues <https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html>`_
* CloudWatch Events rule targets, including
  `CloudWatch Scheduled Events <https://docs.aws.amazon.com/lambda/latest/dg/with-scheduled-events.html>`_ (see
  `CloudWatch Events Event Examples <http://docs.aws.amazon.com/AmazonCloudWatch/latest/events/EventTypes.html>`_ for a
  list of event types supported by CloudWatch Events)
* `S3 events <https://docs.aws.amazon.com/lambda/latest/dg/with-s3.html>`_
* AWS Step Functions state machine tasks
* `CloudWatch Logs filter subscriptions <https://docs.aws.amazon.com/lambda/latest/dg/services-cloudwatchlogs.html>`_
* `DynamoDB stream events <https://docs.aws.amazon.com/lambda/latest/dg/with-ddb.html>`_

Possible future event sources to support:

* Kinesis stream events
* SES (email) events

AWS Step Functions state machines
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Domovoi supports AWS Lambda integration with `AWS Step Functions
<https://aws.amazon.com/documentation/step-functions>`_. Step Functions state machines can be started using the
`StartExecution <http://docs.aws.amazon.com/step-functions/latest/apireference/API_StartExecution.html>`_ method or the
`API Gateway Step Functions integration
<http://docs.aws.amazon.com/step-functions/latest/dg/tutorial-api-gateway.html>`_.

See the `domovoi/examples <domovoi/examples>`_ directory for examples of Domovoi ``app.py`` apps using a state machine,
including a loop that restarts the Lambda when it's about to hit its execution time limit, and a threadpool pattern that
divides work between multiple Lambdas.

When creating a Step Functions State Machine driven Domovoi daemon Lambda, the State Machine assumes the same IAM role as
the Lambda itself. To allow the State Machine to invoke the Lambda, edit the IAM policy (under your app directory, in
``.chalice/policy-dev.json``) to include a statement allowing the "lambda:InvokeFunction" action on all resources, or on the
ARN of the Lambda itself.

Configuration
~~~~~~~~~~~~~

Dead Letter Queues
^^^^^^^^^^^^^^^^^^
To enable your Lambda function to forward failed invocation notifications to `dead letter queuees
<http://docs.aws.amazon.com/lambda/latest/dg/dlq.html>`_, set the configuration key ``dead_letter_queue_target_arn`` in
the file ``.chalice/config.json`` to the target DLQ ARN. For example::

  {
    "app_name": "my_app",
    ...
    "dead_letter_queue_target_arn": "arn:aws:sns:us-east-1:123456789012:my-dlq"
  }

You may need to update your Lambda IAM policy (``.chalice/policy-dev.json``) to give your Lambda access to SNS or SQS.

Concurrency Reservations
^^^^^^^^^^^^^^^^^^^^^^^^
For high volume Lambda invocations in accounts with multiple Lambdas, you may need to set `per-function concurrency
limits <https://docs.aws.amazon.com/lambda/latest/dg/concurrent-executions.html>`_ to partition the overall concurrency
quota and prevent one set of Lambdas from overloading another. In Domovoi, you can do so by setting the configuration
key ``reserved_concurrent_executions`` in the file ``.chalice/config.json`` to the desired concurrency reservation. For
example::

  {
    "app_name": "my_app",
    ...
    "reserved_concurrent_executions": 500
  }


Links
-----
* `Project home page (GitHub) <https://github.com/kislyuk/domovoi>`_
* `Documentation (Read the Docs) <https://domovoi.readthedocs.org/en/latest/>`_
* `Package distribution (PyPI) <https://pypi.python.org/pypi/domovoi>`_
* `Change log <https://github.com/kislyuk/domovoi/blob/master/Changes.rst>`_

Bugs
~~~~
Please report bugs, issues, feature requests, etc. on `GitHub <https://github.com/kislyuk/domovoi/issues>`_.

License
-------
Licensed under the terms of the `Apache License, Version 2.0 <http://www.apache.org/licenses/LICENSE-2.0>`_.

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