Clusters

Flambé supports running remote Runnables where jobs can be distributed across a cluster of workers.

Overall remote architecture

Flambé will create the following cluster when running a Cluster:

../_images/remote-arch.png

Orchestrator

The Orchestrator is the main machine in the cluster. The Orchestrator might host websites, run docker containers, etc. It can also collect artifacts like checkpoints or logs.

Attention

This machine doesn’t need to contain a GPU as it does not perform heavy computations.

Factories

The factories are instances that are capable of doing heavy computational work and likely need to have GPU resources (for example, if you’re running an Experiment with PyTorch and CUDA).

Important

Orchestrator and Factories have private SSH connection with a pair of keys that are create and distributed specially for the specific Cluster. More information about this here.

Launching a cluster

Cluster is a special type of Runnable implementation that handles clusters of machines (e.g. AWS instances) that are capable of running distributed jobs. As with any Runnable, you can run a cluster by executing flambé with the YAML config as an argument:

flambe cluster.yaml

Attention

Cluster is an abstract class because it depends on the cloud service provider, so users will need to use one of the provided implementations or create a custom one by overriding the abstract methods.

Important

We currently provide a full cluster implementation for AWS; see Using AWS

Setting the cluster up

All implementations of Cluster support setting setup_cmds, which are a list of bash commands that will run on all instances after creating the cluster:

!XXXCluster

name: my_cluster

...

setup_cmds:
  - sshfs [email protected]:/path/to/remote /path/to/local/mount/point  # Mount a remote filesystem
  - pip config set index_url https://my-custom-pypi.com  # Configure PyPI

Note that all commands will run sequentially in all the hosts of the cluster.

Tip

This could be useful for mounting volumes, configuring tools or install binaries.

Attention

If you need more complex setup you can also create your own base images for the hosts. AWSCluster supports specifying AMIs for both the Orchestrator and factories.

Submitting Jobs to a Cluster

A cluster is able to run any ClusterRunnable implementation, for example Experiment (more information ` in Cluster Runnables).

Given an experiment.yaml config file, running it remotely is as easy as:

flambe experiment.yaml --cluster cluster.yaml [--force]

Flambé will take care of preparing the cluster to run the ClusterRunnable (in this case an Experiment).

Important

--force option is necessary when an existing execution is taking place in the same cluster and the user wants to override it.

Important

There is no need to run flambe cluster.yaml before running a ClusterRunnable in it. If it’s the first time using the cluster, flambé will create it for you!

Using AWS

We provide full AWS integration using the AWSCluster implementation. When using this cluster, flambé will take care of:

  • Building the cluster
  • Preparing all instances (e.g. installing the version of flambé that matches what the user has locally)
  • Automatically shutting the cluster down (if specified)

How to use AWSCluster?

A AWSCluster is like any flambé Runnable and therefore it can be specified in a YAML format:

!AWSCluster

name: name-of-the-cluster # Pick a unique identifier for the cluster

factories_num: 1  # The amount of factories

factories_type: g3.4xlarge  # The type of factories. GPU instances are recommended.
orchestrator_type: t3.large # The type of the orchestrator (GPU is not necessary).

orchestrator_timeout: -1  # # -1 means the orchestrator will have to be killed manually (recommended)
factories_timeout: -1 # Factories timeout after being unused for these many hours

creator: [email protected]
key_name: aws-key-name

tags:  # Extra tags to add to all instances
    company: my-company

key: /path/to/ssh/key

subnet_id: subnet-abcdef
volume_size: 100. # GBs of disk space for all instances

security_group: sg-0987654321

For a full description, see flambe.cluster.AWSCluster.

Automatic shutdown

This AWSCluster implementation provides a way of automatically shutting down all instances that have been created:

!AWSCluster

# rest of manager config

orchestrator_timeout: 5
factories_timeout: 0

These parameters specify how many hours the resources will persist with low CPU consumption.

In the above example, the Orchestrator will be terminated after 5 hours of low CPU usage. The Factories will be terminated as soon as CPU usage goes down.

Use -1 to keep the resources alive permanently, or until you manually stop them.

See also

For a full example of a configuration file for a Cluster, go here.

Intelligent versioning

When running ClusterRunnables remotely, the correct version of Flambé will be installed automatically, i.e. the version being used locally. For example, if the user has flambe==1.2 installed locally, then all instances (orchestrator and factories) will be using version 1.2!

Attention

This is also valid in developer mode. More on developer mode in Debugging.

Cluster Runnables

A ClusterRunnable is a special implementation of a Runnable that is able to execute on a flambé cluster.

The Experiment object, for example, is a ClusterRunnable.

Users are able to create custom ClusterRunnables by implementing its interface (which extends from the Runnable interface as well).

This new interface requires an additional implementation for the setup() method:

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from flambe.runnable import ClusterRunnable

class MyClusterRunnable(ClusterRunnable):

   def setup(self, cluster: Cluster,
             extensions: Dict[str, str],
             force: bool, **kwargs) -> None:
          # code to setup the cluster

The setup() method should prepare the cluster (which is received as a parameter) to run the Runnable remotely. This usually involves creating folders, downloading resources, running docker containers, etc.

Important

All Cluster implementations provides basic functionality that allow directory creation, running bash commands, rsyncing folders, running docker containers and much more. See its documentation for more information about this.

Hint

It’s highly likely that you will need to change some instance attributes in the object in the setup() method. For doing this, you should use set_serializable_attr() to ensure that the attribute change is serializable.

How to run a ClusterRunnable

For running a ClusterRunnable remotely, you will need to provide a cluster configuration:

flambe cluster_runnable.yaml --cluster cluster.yaml

Because of being Runnable, it can still be executed locally:

flambe cluster_runnable.yaml

Remote Experiments

Users can get the most of performance by running Experiments in a Cluster.

In remote Experiments, a ray cluster will be created connecting all instances in the cluster. The Orchestrator will host Tensorboard and the Report Site (the URL will be provided in the console) and the Factories will do the heavy work executing the pipeline.

Additionally, when running remote Experiments, flambé will take care of uploading the local resources that were specified, making them available to all instances.