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Wednesday 23 May 2018

LocalStack - A fully functional local AWS cloud stack

A fully functional local AWS cloud stack. Develop and test your cloud apps offline!


LocalStack provides an easy-to-use test/mocking framework for developing Cloud applications.
Currently, the focus is primarily on supporting the AWS cloud stack.

Announcements

  • 2018-01-10: Help wanted! Please fill out this survey to support a research study on the usage of Serverless and Function-as-a-Service (FaaS) services, conducted at Chalmers University of Technology. The survey only takes 5-10 minutes of your time. Many thanks for your participation!!
  • 2017-08-27: We need your support! LocalStack is growing fast, we now have thousands of developers using the platform on a regular basis. Last month we have recorded a staggering 100k test runs, with 25k+ DynamoDB tables, 20k+ SQS queues, 15k+ Kinesis streams, 13k+ S3 buckets, and 10k+ Lambda functions created locally - for 0$ costs (more details to be published soon). Bug and feature requests are pouring in, and we now need some support from you to keep the open source version actively maintained. Please check out Open Collective and become a backer or supporter of the project today! Thanks everybody for contributing. ♥
  • 2017-07-20: Please note: Starting with version 0.7.0, the Docker image will be pushed and kept up to date under the new name localstack/localstack. (This means that you may have to update your CI configurations.) Please refer to the updated End-User License Agreement (EULA) for the new versions. The old Docker image (atlassianlabs/localstack) is still available but will not be maintained any longer.

Overview

LocalStack spins up the following core Cloud APIs on your local machine:
Additionally, LocalStack provides a powerful set of tools to interact with the cloud services, including a fully featured KCL Kinesis client with Python binding, simple setup/teardown integration for nosetests, as well as an Environment abstraction that allows to easily switch between local and remote Cloud execution.

Why LocalStack?

LocalStack builds on existing best-of-breed mocking/testing tools, most notably kinesalite/dynalite and moto. While these tools are awesome (!), they lack functionality for certain use cases. LocalStack combines the tools, makes them interoperable, and adds important missing functionality on top of them:
  • Error injection: LocalStack allows to inject errors frequently occurring in real Cloud environments, for instance ProvisionedThroughputExceededException which is thrown by Kinesis or DynamoDB if the amount of read/write throughput is exceeded.
  • Actual HTTP REST services: All services in LocalStack allow actual HTTP connections on a TCP port. In contrast, moto uses boto client proxies that are injected into all methods annotated with @mock_sqs. These client proxies do not perform an actual REST call, but rather call a local mock service method that lives in the same process as the test code.
  • Language agnostic: Although LocalStack is written in Python, it works well with arbitrary programming languages and environments, due to the fact that we are using the actual REST APIs via HTTP.
  • Isolated processes: All services in LocalStack run in separate processes. The overhead of additional processes is negligible, and the entire stack can easily be executed on any developer machine and CI server. In moto, components are often hard-wired in RAM (e.g., when forwarding a message on an SNS topic to an SQS queue, the queue endpoint is looked up in a local hash map). In contrast, LocalStack services live in isolation (separate processes available via HTTP), which fosters true decoupling and more closely resembles the real cloud environment.
  • Pluggable services: All services in LocalStack are easily pluggable (and replaceable), due to the fact that we are using isolated processes for each service. This allows us to keep the framework up-to-date and select best-of-breed mocks for each individual service.

Requirements

  • make
  • python (both Python 2.x and 3.x supported)
  • pip (python package manager)
  • npm (node.js package manager)
  • java/javac (Java 8 runtime environment and compiler)
  • mvn (Maven, the build system for Java)

Installing

The easiest way to install LocalStack is via pip:
pip install localstack
Once installed, run the infrastructure using the following command:
localstack start
Note: Please do not use sudo or the root user - LocalStack should be installed and started entirely under a local non-root user. If you have problems with permissions in MacOS X Sierra, install with pip install --user localstack

Running in Docker

You can also spin up LocalStack in Docker:
localstack start --docker
(Note that on MacOS you may have to run TMPDIR=/private$TMPDIR localstack start --docker if $TMPDIR contains a symbolic link that cannot be mounted by Docker.)
Or using docker-compose (you need to clone the repository first):
docker-compose up
(Note that on MacOS you may have to run TMPDIR=/private$TMPDIR docker-compose up if $TMPDIR contains a symbolic link that cannot be mounted by Docker.)

Configurations

You can pass the following environment variables to LocalStack:
  • SERVICES: Comma-separated list of service names and (optional) ports they should run on. If no port is specified, a default port is used. Service names basically correspond to the service names of the AWS CLI (kinesis, lambda, sqs, etc), although LocalStack only supports a subset of them. Example value: kinesis,lambda:4569,sqs:4570 to start Kinesis on the default port, Lambda on port 4569, and SQS on port 4570.
  • DEFAULT_REGION: AWS region to use when talking to the API (defaults to us-east-1).
  • HOSTNAME: Name of the host to expose the services internally (defaults to localhost). Use this to customize the framework-internal communication, e.g., if services are started in different containers using docker-compose.
  • HOSTNAME_EXTERNAL: Name of the host to expose the services externally (defaults to localhost). This host is used, e.g., when returning queue URLs from the SQS service to the client.
  • USE_SSL: Whether to use https://... URLs with SSL encryption (defaults to false).
  • KINESIS_ERROR_PROBABILITY: Decimal value between 0.0 (default) and 1.0 to randomly inject ProvisionedThroughputExceededException errors into Kinesis API responses.
  • DYNAMODB_ERROR_PROBABILITY: Decimal value between 0.0 (default) and 1.0 to randomly inject ProvisionedThroughputExceededException errors into DynamoDB API responses.
  • LAMBDA_EXECUTOR: Method to use for executing Lambda functions. Possible values are:
    • local: run Lambda functions in a temporary directory on the local machine
    • docker: run each function invocation in a separate Docker container
    • docker-reuse: create one Docker container per function and reuse it across invocations
    For docker and docker-reuse, if LocalStack itself is started inside Docker, then the docker command needs to be available inside the container (usually requires to run the container in privileged mode). Default is docker, fallback to local if Docker is not available.
  • LAMBDA_REMOTE_DOCKER determines whether Lambda code is copied or mounted into containers. Possible values are:
    • true (default): your Lambda function definitions will be passed to the container by copying the zip file (potentially slower). It allows for remote execution, where the host and the client are not on the same machine.
    • false: your Lambda function definitions will be passed to the container by mounting a volume (potentially faster). This requires to have the Docker client and the Docker host on the same machine.
  • DATA_DIR: Local directory for saving persistent data (currently only supported for these services: Kinesis, DynamoDB, Elasticsearch, S3). Set it to /tmp/localstack/data to enable persistence (/tmp/localstack is mounted into the Docker container), leave blank to disable persistence (default).
  • PORT_WEB_UI: Port for the Web user interface (dashboard). Default is 8080.
  • <SERVICE>_BACKEND: Custom endpoint URL to use for a specific service, where <SERVICE> is the uppercase service name (currently works for: APIGATEWAY, CLOUDFORMATION, DYNAMODB, ELASTICSEARCH, KINESIS, S3, SNS, SQS). This allows to easily integrate third-party services into LocalStack.
  • FORCE_NONINTERACTIVE: when running with Docker, disables the --interactive and --tty flags. Useful when running headless.
Additionally, the following read-only environment variables are available:
  • LOCALSTACK_HOSTNAME: Name of the host where LocalStack services are available. This is needed in order to access the services from within your Lambda functions (e.g., to store an item to DynamoDB or S3 from Lambda). The variable LOCALSTACK_HOSTNAME is available for both, local Lambda execution (LAMBDA_EXECUTOR=local) and execution inside separate Docker containers (LAMBDA_EXECUTOR=docker).

Accessing the infrastructure via CLI or code

You can point your aws CLI to use the local infrastructure, for example:
aws --endpoint-url=http://localhost:4568 kinesis list-streams
{
    "StreamNames": []
}
NEW: Check out awslocal, a thin CLI wrapper that runs commands directly against LocalStack (no need to specify --endpoint-url anymore). Install it via pip install awscli-local, and then use it as follows:
awslocal kinesis list-streams
{
    "StreamNames": []
}
UPDATE: Use the environment variable $LOCALSTACK_HOSTNAME to determine the target host inside your Lambda function. See Configurations section for more details.

Client Libraries

from  https://github.com/localstack/localstack
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