Deploy a batch machine learning workload

This tutorial demonstrates how to use Google Kubernetes Engine (GKE) to manage fault-tolerant batch workloads while keeping your costs low. Follow this tutorial to learn how to use Jobs and cost-optimized Spot Pods, as well as how to configure an in-cluster Redis job queue on GKE.

Background

A batch workload is a process typically designed to have a start and a completion point. You should consider batch workloads on GKE if your architecture involves ingesting, processing, and outputting data instead of using raw data. Areas like machine learning, artificial intelligence, and high performance computing (HPC) feature different kinds of batch workloads, such as offline model training, batched prediction, data analytics, simulation of physical systems, and video processing.

By designing containerized batch workloads, you can leverage the following GKE benefits:

• An open standard, broad community, and managed service.
• Cost efficiency from effective workload and infrastructure orchestration and specialized compute resources.
• Isolation and portability of containerization, allowing the use of cloud as overflow capacity while maintaining data security.
• Availability of burst capacity, followed by rapid scale down of GKE clusters.

Prepare the environment

1. Clone the sample repository used in this tutorial:

   git clone https://github.com/GoogleCloudPlatform/kubernetes-engine-samples
   cd kubernetes-engine-samples/batch/aiml-workloads
   

2. Create a GKE Autopilot cluster:

   gcloud container clusters create-auto batch-aiml \
       --location=us-central1
   

   This step can take up to 5 minutes to complete.

Set up dataset storage with a Network File System (NFS)

The machine learning workload requires a storage solution for the datasets and output files. In this section, you create a Filestore instance and provide access to the instanceby using a PersistentVolume and a PersistentVolumeClaim.

To learn more, see how to design an optimal storage strategy and how to access Filestore instances from GKE clusters.

Create a Filestore instance

1. Create a Filestore instance:

   gcloud filestore instances create batch-aiml-filestore \
       --zone=us-central1-b \
       --tier=BASIC_HDD \
       --file-share=name="NFSVol",capacity=1TB \
       --network=name="default"
   

   This command specifies the following options:

   • tier: The service tier for the Filestore instance. This sample uses the basic tier. To learn about the other options, refer to Service tiers.

   • network=name: The name of the Virtual Private Cloud (VPC) network for the Filestore instance. The GKE cluster must be in the same VPC network as the Filestore instance.

   • capacity: The desired size of the volume. Specify the storage value in one of the supported units described in Resource quantities.

   Note: This step can take up to 5 minutes to complete.

2. Verify that the Filestore instance has been deployed:

   gcloud filestore instances list \
       --project=PROJECT_ID \
       --zone=us-central1-b
   

   Replace PROJECT_ID with your Google Cloud project ID.

   The output is similar to the following:

   INSTANCE_NAME: batch-aiml-filestore
   LOCATION: us-central1-b
   TIER: BASIC_HDD
   CAPACITY_GB: 1024
   FILE_SHARE_NAME: NFSVol
   IP_ADDRESS: 203.0.113.54
   STATE: READY
   CREATE_TIME: 2022-03-15T18:23:51
   

3. Note the value in the IP_ADDRESS field to use in the following section.

Create a PersistentVolume

A Kubernetes PersistentVolume specification allows the GKE cluster to connect to the Filestore instance.

1. Update the kubernetes-manifests/persistent-volume.yaml file with the Filestore instance IP address:

   sed -i "\
     s/<FILESTORE_IP_ADDRESS>/IP_ADDRESS/g" \
     kubernetes-manifests/persistent-volume.yaml
   

   Replace IP_ADDRESS with the IP address that you noted when creating the Filestore instance in the preceding section.

2. Deploy the PersistentVolume:

   kubectl apply -f kubernetes-manifests/persistent-volume.yaml
   

Create a PersistentVolumeClaim

A Kubernetes PersistentVolumeClaim allows Kubernetes Pods and Jobs to access the storage resources of a PersistentVolume.

Deploy the PersistentVolumeClaim:

kubectl apply -f kubernetes-manifests/persistent-volume-claim.yaml

Consume the PersistentVolumeClaim

With the PersistentVolume and PersistentVolumeClaim set up on the GKE cluster, you can configure the Redis server and the batch jobs to consume the PersistentVolumeClaim. This appears as a mountable storage volume.

Inspect the kubernetes-manifests/redis-pod.yaml and kubernetes-manifests/workload.yaml files. The manifest configurations are similar to the following:

  spec:
  …
  containers:
  - name: workload
    image: "us-central1-docker.pkg.dev/gke-batch-aiml/batch-aiml-docker-repo/workload"
    volumeMounts:
    - mountPath: /mnt/fileserver
      name: workload-pvc
  volumes:
  - name: workload-pvc
    persistentVolumeClaim:
      claimName: fileserver-claim
      readOnly: false

In this manifest:

• spec.volumes specifies the PersistentVolumeClaim to consume.
• spec.containers.volumeMounts specifies the local file path where the Pod can access the Filestore fileshare.

Set up a Redis job queue

The workload processes data in batches to iteratively train a fraud detection model. To manage the datasets currently being processed or still in the queue, you deploy the Redis server into the GKE cluster.

For this tutorial, you start a single instance of Redis. To deploy Redis scalably and redundantly, refer to Create a multi-tier web application with Redis and PHP.

1. Deploy the Redis server specification.

   kubectl apply -f kubernetes-manifests/redis-pod.yaml
   

2. Verify that the Pod is running:

   kubectl get pods
   

   The output is similar to the following:

   NAME           READY   STATUS    RESTARTS   AGE
   redis-leader   1/1     Running   0          118s
   

   The Pod might take up to two minutes to start running.

3. Transfer the files containing the training and testing datasets to the NFS volume.

   sh scripts/transfer-datasets.sh
   

   This script copies the files from the sample code repository to the /mnt/fileserver/datasets/ directory on the redis-leader Pod.

4. Populate the Redis queue.

   sh scripts/queue-jobs.sh
   

   This script pushes the file paths for the training datasets to a list named datasets in the Redis database. This queue will be used by the workload to locate the next dataset to process.

5. Deploy the Service to make the Redis server discoverable within the GKE cluster.

   kubectl apply -f ./kubernetes-manifests/redis-service.yaml
   

Run the batch workload

At this point, you prepared the GKE cluster, the Redis job queue, and fileshare. Now, you can run your batched workload.

In this section, you use a container image of a sample workload for training a fraud detection model using batches of financial transaction data. The training process can be summarized as follows:

1. A Redis client claims jobs (file paths to datasets) in the Redis queue, and removes them from the queue when completed.

2. A model training manager class, FraudDetectionModelTrainer, loads a new batch of data and, optionally, a saved state of a machine learning model. The dataset is used to refine the model (a process known as "warm-start" training).

3. The new state of the model and a report of the batch details and performance scores are saved in the Filestore NFS volume, which can be accessed in the GKE cluster using a PersistentVolumeClaim.

To learn more, explore the source code.

Define the Job

The following manifest describes the Kubernetes Job for the batch workload image. A Job controller in Kubernetes creates one or more Pods and ensures that they successfully execute a specific task.

apiVersion: batch/v1
kind: Job
metadata:
  name: workload
spec:
  parallelism: 1
  template:
    metadata:
      name: workload
    spec:
      nodeSelector:
        cloud.google.com/gke-spot: "true"
      containers:
      - name: workload
        image: "us-docker.pkg.dev/google-samples/containers/gke/batch-ml-workload"
        volumeMounts:
        - mountPath: /mnt/fileserver
          name: workload-pvc
      volumes:
      - name: workload-pvc
        persistentVolumeClaim:
          claimName: fileserver-claim
          readOnly: false
      restartPolicy: OnFailure

Note: If you configure a workload where batches can be run in parallel (e.g. classifying batches of images, long-running data analysis, etc), you can increase the parallelism value to allow that many Pods to run the job concurrently until the completion condition is met. The nodeSelector specification tells GKE to use Spot Pods.

Deploy the workload

1. Deploy the Job:

   kubectl apply -f ./kubernetes-manifests/workload.yaml
   

2. Check if the status of the workload-XXX Pod is Completed:

   watch kubectl get pods
   

   This might take a few seconds. You can return to the command line by pressing Ctrl+C.

   The output is similar to the following:

   NAME             READY   STATUS      RESTARTS   AGE
   redis-leader     1/1     Running     0          16m
   workload-4p55d   0/1     Completed   0          83s
   

3. Check the logs from the workload Job:

   kubectl logs job/workload
   

   The output is similar to the following:

   Worker with sessionID: b50f9459-ce7f-4da8-9f84-0ab5c3233a72
   Initial queue state: empty=False
   Processing dataset: datasets/training/2018-04-04.pkl
   Processing dataset: datasets/training/2018-04-03.pkl
   Processing dataset: datasets/training/2018-04-02.pkl
   Processing dataset: datasets/training/2018-04-01.pkl
   Queue empty, exiting
   

   The .pkl files are serializations of datasets containing a batch of credit card transactions, marked valid or fraudulent. The workload Job iterates over these files, unpacking the datasets and using them to train the machine learning model, before removing them from the Redis queue. The workload continues to process the data in batches, until the Redis queue is emptied, before exiting with success.

Explore the NFS volume

During its operation the workload creates files in the mounted NFS volume, accessible across the cluster by other batch jobs or online applications.

1. List the files created by the workload:

   kubectl exec --stdin --tty redis-leader -- /bin/sh -c "ls -1 /mnt/fileserver/output"
   

   The output should be the following:

   model_cpt_2018-04-01.pkl
   model_cpt_2018-04-02.pkl
   model_cpt_2018-04-03.pkl
   model_cpt_2018-04-04.pkl
   report.txt
   

   Checkpoints for the trained model (filenames like model_cpt_XXX.pkl) and a report of the model performance (report.txt) were created in the /mnt/fileserver/output directory on the NFS volume.

2. Inspect the model performance report:

   kubectl exec --stdin --tty redis-leader -- /bin/sh -c "cat /mnt/fileserver/output/report.txt"
   

   The following is a snippet from the output:

   Report generated on: 2022-02-09 14:19:42.303619
   Training dataset: 2018-04-04.pkl
   Model checkpoint: model_cpt_2018-04-04.pkl
   ---
   Accuracy on training data: 0.9981112277019937
   Accuracy on testing data: 0.9977204434773599
   

   The file contains entries detailing the time of training, dataset used, accuracy achieved, and the filename of the model checkpoint associated with the training.

To learn more about NFS volumes, check out the Filestore guides.