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Embargo: network fault testing with Docker

Project description

Embargo is a fork of blockade. We have decided to fork blockade because the original project has not been maintained for years. The main difference between the original and this fork is that support for python 2 is dropped and python 3.6 and 3.7 should be supported. More changes should be on the way.

Embargo is a utility for testing network failures and partitions in distributed applications. Embargo uses Docker containers to run application processes and manages the network from the host system to create various failure scenarios.

A common use is to run a distributed application such as a database or cluster and create network partitions, then observe the behavior of the nodes. For example in a leader election system, you could partition the leader away from the other nodes and ensure that the leader steps down and that another node emerges as leader.

Check out the full documentation for details.

Embargo features:

  • A flexible YAML format to describe the containers in your application
  • Support for dependencies between containers, using named links
  • A CLI tool for managing and querying the status of your embargo
  • Creation of arbitrary partitions between containers
  • Giving a container a flaky network connection to others (drop packets)
  • Giving a container a slow network connection to others (latency)
  • While under partition or network failure control, containers can freely communicate with the host system – so you can still grab logs and monitor the application.

Blockade was originally developed by the Dell Cloud Manager (formerly Enstratius) team. Blockade was inspired by the excellent Jepsen series.

Requirements

  • docker (>= 1.4.0 due to docker-py)
  • iproute2 tools (ip and tc specifically)

Configuration

Embargo expects a embargo.yaml file in the current directory which describes the containers to launch, how they are linked, and various parameters for the embargo modes. Example:

containers:
  c1:
    image: my_docker_image
    command: /bin/myapp
    volumes:
      "/opt/myapp": "/opt/myapp_host"
    expose: [80]
    environment:
      "IS_MASTER": 1
    ports:
      81: 80

  c2:
    image: my_docker_image
    command: /bin/myapp
    volumes: ["/data"]
    expose: [80]
    links:
      c1: master

  c3:
    image: my_docker_image
    command: /bin/myapp
    expose: [80]
    links:
      c1: master

network:
  flaky: 30%
  slow: 75ms 100ms distribution normal

Embargo stores transient information in a local .embargo/ directory. This directory will be cleaned up automatically when you run the embargo destroy command.

Usage

Embargo may be used from the command line manually. The commands are also intended to be easy to wrap and automate within tests, etc.

Commands

embargo up

Start the containers and link them together, if necessary.

embargo destroy

Destroys all containers and restore networks.

embargo status

Print the status of the containers and embargo.

embargo flaky n1

embargo flaky n1 n2

Make network flaky to one or more containers.

embargo slow n1

Make network slow to one or more containers.

embargo duplicate n1

Toggle sporadic duplicate packets in the network of one or more containers.

embargo fast n1

Restore network speed and reliability to one or more containers.

embargo partition n1,n2

embargo partition n1,n2 n3,n4

Create one or more network partitions. Each partition is specified as a comma-separated list. Containers may not exist in more than one partition. Containers not specified are grouped into an implicit partition. Each partition command replaces any previous partition or block rules.

embargo join

Remove all partitions between containers.

embargo random-partition

Introduce one or many random partitions among the configured nodes.

License

Embargo is offered under the Apache License 2.0.

Development

Install test dependencies with pip install embargo[test].

You can run integration tests in a Vagrant VM using the included Vagrantfile. Run vagrant up and Docker will be installed in your VM and tests run. You can rerun them with vagrant provision, or SSH into the VM and run them yourself, from /vagrant.

Embargo documentation is built with Sphinx and is found under docs/. To build:

$ pip install -r requirements_docs.txt
$ cd docs/
$ make html

HTML output will be under docs/_build/html/.

The documentation is also hosted online.

Changelog

0.1.1 (2019-05-01)

  • Added updated maintainers.
  • Refactored code (renamed blockade to embargo in code).
  • Updated README.md

0.1.0 (2019-05-01)

  • Initial release of Embargo!

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