The blockade configuration file is conventionally named blockade.yaml and is used to describe the containers in your application. Here is an example:

    image: my_docker_image
    command: /bin/myapp
    volumes: {"/opt/myapp": "/opt/myapp_host"}
    expose: [80]
    ports: {8080: 80}
    environment: {"IS_MASTER": 1}

    image: my_docker_image
    command: /bin/myapp
    volumes: ["/data"]
    links: {c1: master}

    image: my_docker_image
    command: /bin/myapp
    links: {c1: master}

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

The format is YAML and there are two important sections: containers and network.


Containers are described as a map with the key as the Blockade container name (c1, c2, c3 in the example above). This key is used for commands to manipulate the Blockade and is also used as the hostname of the container.

Each entry in the containers section is a single Docker container in the Blockade. Each container parameter controls how the container is launched. Most are simply pass-throughs to Docker. Many valuable details can be found in the Docker run command documentation.


image is required and specifies the Docker image name to use for the container. The image must exist in your Docker installation.


command is optional and specifies the command to run within the container. If not specified, a default command must be part of the image you are using. You may include environment variables in this command, but to do so you must typically wrap the command in a shell, like sh -c "/bin/myapp $MYENV".


volumes is optional and specifies the volumes to mount in the container, from the host. Volumes can be specified as either a map or a list. In map form, the key is the path on the host to expose and the value is the mountpoint within the container. In list form, the host path and container mountpoint are assumed to be the same. See the Docker volumes documentation for details about how this works.


expose is optional and specifies ports to expose from the container. Ports must be exposed in order to use the Docker named links feature.


ports is optional and specifies ports published to the host machine. It is a dictionary from external port to internal container port.


environment is optional and specifies environment variables for command. See more details in command section above.


hostname is optional and gives the ability to redefine hostname of a container.


dns is optional and specifies a list of DNS-servers for container.


start_delay is optional and specifies a number of seconds to wait before starting a container. This can be used as a stopgap way to ensure a dependent service is running before starting a container.


count is optional and specifies the number of copies of the container to launch.


cap_add is optional and specifies additional root capabilities


container_name is optional and specifies a custom container name, instead of letting blockade generate one. Use caution with this setting, because Docker enforces uniqueness of names across all containers.

When this parameter is combined with count, an underscore and index will be suffixed to this name. For example “app” becomes “app_1”, “app_2”, etc.


The network configuration block controls the settings used for network filter commands like slow and flaky. If unspecified, defaults will be used. There are two parameters:


slow controls the amount and distribution of delay for network packets when a container is in the Blockade slow state. It is specified as an expression understood by the tc netem traffic control delay facility. See the man page for details, but the pattern is:

    [ distribution { uniform | normal | pareto |  paretonormal } ]

TIME and JITTER are expressed in milliseconds while CORRELATION is a percentage.


flaky controls the lossiness of network packets when a contrainer is in the Blockade flaky state. It is specified as an expression understood by the tc netem traffic control loss facility. See the man page for details, but the simplified pattern is:


PERCENT and CORRELATION are both expressed as percentages.


driver specifies docker network stack. default will use standard Docker networking, that allows to connect containers by links. Other option is udn. It will enable user defined network, that performs dns resolution of running containers and allows to create any-to-any communications. In case of udn network environment variables with links will not bet set.