Blockade
Blockade is a utility for testing network failures and partitions in distributed applications. Blockade 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.
Blockade 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 blockade
- 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 is written and maintained by the Dell Cloud Manager (formerly Enstratius) team and is used internally to test the behaviors of our software. We also release a number of other internal components as open source, most notably Dasein Cloud.
Inspired by the excellent Jepsen series.
Requirements
- docker (>= 1.4.0 due to docker-py)
- iproute2 tools (
ip
andtc
specifically)
Configuration
Blockade expects a blockade.yaml
file in the current directory which
describes the containers to launch, how they are linked, and various
parameters for the blockade 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
Blockade stores transient information in a local .blockade/
directory.
This directory will be cleaned up automatically when you run the
blockade destroy
command.
Usage
Blockade may be used from the command line manually. The commands are also intended to be easy to wrap and automate within tests, etc.
Commands
blockade up
Start the containers and link them together, if necessary.
blockade destroy
Destroys all containers and restore networks.
blockade status
Print the status of the containers and blockade.
blockade flaky n1
blockade flaky n1 n2
Make network flaky to one or more containers.
blockade slow n1
Make network slow to one or more containers.
blockade duplicate n1
Toggle sporadic duplicate packets in the network of one or more containers.
blockade fast n1
Restore network speed and reliability to one or more containers.
blockade partition n1,n2
blockade 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.
blockade join
Remove all partitions between containers.
blockade random-partition
Introduce one or many random partitions among the configured nodes.
License
Blockade is offered under the Apache License 2.0.
Development
Install test dependencies with pip install blockade[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
.
Blockade 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.