Containerizers

Motivation

Containerizers are used to run tasks in ‘containers’, which in turn are used to:

• Isolate a task from other running tasks.
• ‘Contain’ tasks to run in limited resource runtime environment.
• Control a task’s resource usage (e.g., CPU, memory) programatically.
• Run software in a pre-packaged file system image, allowing it to run in different environments.

Types of containerizers

Mesos plays well with existing container technologies (e.g., docker) and also provides its own container technology. It also supports composing different container technologies (e.g., docker and mesos).

Mesos implements the following containerizers:

• Composing
• Docker
• Mesos (default)

User can specify the types of containerizers to use via the agent flag --containerizers.

### Composing containerizer

This feature allows multiple container technologies to play together. It is enabled when you configure the --containerizers agent flag with multiple comma seperated containerizer names (e.g., --containerizers=mesos,docker). The order of the comma separated list is important as the first containerizer that supports the task’s container configuration will be used to launch the task.

Use cases:

• For testing tasks with different types of resource isolations. Since ‘mesos’ containerizers have more isolation abilities, a framework can use composing containerizer to test a task using ‘mesos’ containerizer’s controlled environment and at the same time test it to work with ‘docker’ containers by just changing the container parameters for the task.

### Docker containerizer

Docker containerizer allows tasks to be run inside docker container. This containerizer is enabled when you configure the agent flag as --containerizers=docker.

Use cases:

• If a task needs to be run with the tooling that comes with the docker package.
• If Mesos agent is running inside a docker container.

For more details, see Docker Containerizer.

### Mesos containerizer

This containerizer allows tasks to be run with an array of pluggable isolators provided by Mesos. This is the native Mesos containerizer solution and is enabled when you configure the agent flag as --containerizers=mesos.

Use cases:

• Allow Mesos to control the task’s runtime environment without depending on other container technologies (e.g., docker).
• Want fine grained operating system controls (e.g., cgroups/namespaces provided by Linux).
• Want Mesos’s latest container technology features.
• Need additional resource controls like disk usage limits, which might not be provided by other container technologies.
• Want to add custom isolation for tasks.

For more details, see Mesos Containerizer.

References

• Containerizer Internals for implementation details of containerizers.