embargo 0.1.1
Embargo: network fault testing with Docker

********
EMBARGO
********

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 <http://www.docker.io>`_
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 <http://blockade.readthedocs.org>`_
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 <http://aphyr.com/tags/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:

.. code-block:: yaml

    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:

.. code-block:: bash

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

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

The documentation is also `hosted online <http://blockade.readthedocs.org>`_.


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!