Kubernetes Integration

The steps required for the integration of DBND with your Kubernetes cluster.

Before You Begin


First, you need to configure DBND configure DBND.
Setup your K8S cluster

When you have the Kubernetes cluster and DBND installed, you can make it run.

Verify the Integration with the Kubernetes Cluster

  1. Run the sanity check task on the Kubernetes cluster:
dbnd run dbnd_sanity_check --task-version now --env kubernetes_cluster_env --interactive

In this command, we used the following parameters:

-- env kubernetes_cluster_env is the environment configuration section.
--interactive flag ensures that we will receive all logs from the pods, as well as wait until the run is complete.

  1. To ensure that the task succeeds, run the kubectl get\describe pods command.

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Note

If you defined a new configuration section and are trying to run an already-built DBND image, you might have to compile it by yourself with the new configuration section.

Kubernetes Lifecycle Overview

When you execute a task by using the Kubernetes engine, you initiate a lifecycle for each task.
The lifecycle depends on your configuration. In the sections above, we describe the main lifecycles.

The following CLI switches are useful when you run commands on a Kubernetes cluster:

Command

Description

--interactive

Runs tasks submission in blocking mode. Ensures that the task submitting the smaller tasks (driver) will be run locally. This way you can debug how your pods are created. Waits until the execution is complete and displays all logs for all pods.

--submit-driver

Runs a driver on a remote engine. The driver task (that submits all other tasks) is run remotely inside the Kubernetes pod.

--local-driver

Runs a driver on a local driver. Driver task will be run locally. This way you can debug how your pods are created.

--submit-tasks

Submits tasks from a driver to a remote engine.

--no-submit-tasks

Disables tasks submission so that tasks run in the driver process.

--docker-build-tag

Defines a custom Docker image tag for the Docker image to be be built

Submitted Driver

Take a look at the following example:

dbnd run dbnd_sanity_check --submit-driver --task-version now --env kubernetes_cluster_env

The --submit-driver flag affects where our driver runs, and hence affects the lifecycle.
We run through the following algorithm:

  1. Build a driver task.
  2. Gather all the needed resources and settings to create a pod with a driver task inside.
    -> The pod creation request is sent to the cluster.
  3. Submit the driver task.
    -> The driver task is sent to the Kubernetes and is ran inside the pod. The driver task creates a new pod to run user code.
    4 .Run user tasks within a pod.
    -> The user tasks are executed inside the cluster.
    -> When the user code starts running, the driver gathers output, logs, etc. of the task that was executed. It is in charge of running the next pod when the current pod finishes.
    -> The driver executes the next task until the end of DAG

Local Driver

Now let's look at the following command:

dbnd run dbnd_sanity_check --local-driver --task-version now --env kubernetes_cluster_env

In this command, the --local-driver flag ensures that our driver runs locally and not inside the cluster.

Now, the lifecycle is the following:

  1. Build a driver task and gather all the necessary resources for the driver.
  2. Run the driver task locally.
    -> The driver task is not sent to Kubernetes and is executed on the local engine. The driver still sends pods to in-cluster execution.
  3. The user code runs within pods. User tasks are executed inside the cluster.
  4. When the user code starts running, the driver gathers the logs, outputs, etc. It is in charge of running the next pod when the current pod finishes.
  5. The driver executes the next task until the DAG is completed.

Advance Example

dbnd run dbnd_sanity_check  --task-version now --env=kubernetes_cluster_env --interactive --set-config kubernetes.namespace=my_namespace  --set-config kubernetes.container_tag=dbnd-dbnd_examples-py36-branch-release --set kubernetes.debug=true 

Let's break it down:

  • dbnd run dbnd_sanity_check --task-version now - Basic dbnd command.
  • -env=kubernetes_cluster_env - The environment we want to run with, which is configured to use the k8s engine
  • -interactive - Tells the submitter (local machine) to wait for the run to end.
  • -set-config kubernetes.namespace=my_namespace - The namespace we are using.
  • -set-config kubernetes.container_tag=dbnd-dbnd_examples-py36-branch-release - The image we want to use, built in the same pipelines as the env.
  • -set kubernetes.debug=true - debug flag for kubernetes Executor

Troubleshooting Kubernetes Cluster

When you run your code, you might encounter different issues. DBND provides you with a set of tools that help you understand the underlying cause of a problem. See Kubernetes Troubleshooting

Configuration Parameter

Description

kubernetes.keep_finished_pods=True

When set to True, it never deletes any pods. It is very useful when you try to understand what went wrong inside a pod's execution.

kubernetes.debug=True

Prints all the debug information, most importantly pod events that we receive.


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