K8s User Guide


1. Pull bigdl-k8s Docker Image

You may pull the prebuilt BigDL bigdl-k8s Image from Docker Hub as follows:

sudo docker pull intelanalytics/bigdl-k8s:latest

Speed up pulling image by adding mirrors

To speed up pulling the image from DockerHub, you may add the registry-mirrors key and value by editing daemon.json (located in /etc/docker/ folder on Linux):

{
  "registry-mirrors": ["https://<my-docker-mirror-host>"]
}

For instance, users in China may add the USTC mirror as follows:

{
  "registry-mirrors": ["https://docker.mirrors.ustc.edu.cn"]
}

After that, flush changes and restart docker:

sudo systemctl daemon-reload
sudo systemctl restart docker

2. Launch a Client Container

You can submit BigDL application from a client container that provides the required environment.

sudo docker run -itd --net=host \
    -v /etc/kubernetes:/etc/kubernetes \
    -v /root/.kube:/root/.kube \
    intelanalytics/bigdl-k8s:latest bash

Note: to create the client container, -v /etc/kubernetes:/etc/kubernetes: and -v /root/.kube:/root/.kube are required to specify the path of kube config and installation.

You can specify more arguments:

sudo docker run -itd --net=host \
    -v /etc/kubernetes:/etc/kubernetes \
    -v /root/.kube:/root/.kube \
    -e NOTEBOOK_PORT=12345 \
    -e NOTEBOOK_TOKEN="your-token" \
    -e http_proxy=http://your-proxy-host:your-proxy-port \
    -e https_proxy=https://your-proxy-host:your-proxy-port \
    -e RUNTIME_SPARK_MASTER=k8s://https://<k8s-apiserver-host>:<k8s-apiserver-port> \
    -e RUNTIME_K8S_SERVICE_ACCOUNT=account \
    -e RUNTIME_K8S_SPARK_IMAGE=intelanalytics/bigdl-k8s:latest \
    -e RUNTIME_PERSISTENT_VOLUME_CLAIM=myvolumeclaim \
    -e RUNTIME_DRIVER_HOST=x.x.x.x \
    -e RUNTIME_DRIVER_PORT=54321 \
    -e RUNTIME_EXECUTOR_INSTANCES=1 \
    -e RUNTIME_EXECUTOR_CORES=4 \
    -e RUNTIME_EXECUTOR_MEMORY=20g \
    -e RUNTIME_TOTAL_EXECUTOR_CORES=4 \
    -e RUNTIME_DRIVER_CORES=4 \
    -e RUNTIME_DRIVER_MEMORY=10g \
    intelanalytics/bigdl-k8s:latest bash 
  • NOTEBOOK_PORT value 12345 is a user specified port number.

  • NOTEBOOK_TOKEN value “your-token” is a user specified string.

  • http_proxy/https_proxy is to specify http proxy/https_proxy.

  • RUNTIME_SPARK_MASTER is to specify spark master, which should be k8s://https://<k8s-apiserver-host>:<k8s-apiserver-port> or spark://<spark-master-host>:<spark-master-port>.

  • RUNTIME_K8S_SERVICE_ACCOUNT is service account for driver pod. Please refer to k8s RBAC.

  • RUNTIME_K8S_SPARK_IMAGE is the k8s image.

  • RUNTIME_PERSISTENT_VOLUME_CLAIM is to specify Kubernetes volume mount. We are supposed to use volume mount to store or receive data.

  • RUNTIME_DRIVER_HOST/RUNTIME_DRIVER_PORT is to specify driver localhost and port number (only required when submitting jobs via kubernetes client mode).

  • Other environment variables are for spark configuration setting. The default values in this image are listed above. Replace the values as you need.

Once the container is created, execute the container:

sudo docker exec -it <containerID> bash

You will login into the container and see this as the output:

root@[hostname]:/opt/spark/work-dir# 

/opt/spark/work-dir is the spark work path.

The /opt directory contains:

  • download-bigdl.sh is used for downloading BigDL distributions.

  • start-notebook-spark.sh is used for starting the jupyter notebook on standard spark cluster.

  • start-notebook-k8s.sh is used for starting the jupyter notebook on k8s cluster.

  • bigdl-x.x-SNAPSHOT is BIGDL_HOME, which is the home of BigDL distribution.

  • bigdl-examples directory contains downloaded python example code.

  • install-conda-env.sh is displayed that conda env and python dependencies are installed.

  • jdk is the jdk home.

  • spark is the spark home.

  • redis is the redis home.

3. Submit to k8s from remote

Instead of lanuching a client container, you can also submit BigDL application from a remote node with the following steps:

  1. Check the prerequisites of running Spark on Kubernetes.

    • The remote node needs to properly setup the configurations and authentications of the k8s cluster (e.g. the config file under ~/.kube, especially the server address in the config).

    • Install kubectl on the remote node and run some sample commands for verification, for example kubectl auth can-i <list|create|edit|delete> pods. Note that the installation of kubectl is not a must for the remote node, but it is a useful tool to verify whether the remote node has access to the k8s cluster.

    • The environment variables http_proxy and https_proxy may affect the connection using kubectl. You may check and unset these environment variables in case you get errors when executing the kubectl commands on the remote node.

  2. Follow the steps in the Python User Guide to install BigDL in a conda environment.

4. Run BigDL on k8s

Note: Please make sure kubectl has appropriate permission to create, list and delete pod.

You may refer to Section 5 for some known issues when running BigDL on k8s.

4.1 K8s client mode

We recommend using init_orca_context at the very beginning of your code (e.g. in script.py) to initiate and run BigDL on standard K8s clusters in client mode.

from bigdl.orca import init_orca_context

init_orca_context(cluster_mode="k8s", master="k8s://https://<k8s-apiserver-host>:<k8s-apiserver-port>",
                  container_image="intelanalytics/bigdl-k8s:latest",
                  num_nodes=2, cores=2, memory="2g")

Remark: You may need to specify Spark driver host and port if necessary by adding the argument: conf={"spark.driver.host": "x.x.x.x", "spark.driver.port": "x"}.

Execute python script.py to run your program on k8s cluster directly.

4.2 K8s cluster mode

For k8s cluster mode, you can call init_orca_context and specify cluster_mode to be “spark-submit” in your python script (e.g. in script.py):

from bigdl.orca import init_orca_context

init_orca_context(cluster_mode="spark-submit")

Use spark-submit to submit your BigDL program:

${SPARK_HOME}/bin/spark-submit \
  --master k8s://https://<k8s-apiserver-host>:<k8s-apiserver-port> \
  --deploy-mode cluster \
  --conf spark.kubernetes.authenticate.driver.serviceAccountName=account \
  --name bigdl \
  --conf spark.kubernetes.container.image="intelanalytics/bigdl-k8s:latest" \
  --conf spark.kubernetes.container.image.pullPolicy=Always \
  --conf spark.pyspark.driver.python=./env/bin/python \
  --conf spark.pyspark.python=./env/bin/python \
  --archives path/to/environment.tar.gz#env \
  --conf spark.executor.instances=1 \
  --executor-memory 10g \
  --driver-memory 10g \
  --executor-cores 8 \
  --num-executors 2 \
  --properties-file ${BIGDL_HOME}/conf/spark-bigdl.conf \
  --py-files local://${BIGDL_HOME}/python/bigdl-spark_${SPARK_VERSION}-${BIGDL_VERSION}-python-api.zip,local:///path/script.py
  --conf spark.driver.extraClassPath=local://${BIGDL_HOME}/jars/* \
  --conf spark.executor.extraClassPath=local://${BIGDL_HOME}/jars/* \
  local:///path/script.py

4.3 Run Jupyter Notebooks

After a Docker container is launched and user login into the container, you can start the Jupyter Notebook service inside the container.

In the /opt directory, run this command line to start the Jupyter Notebook service:

./start-notebook-k8s.sh

You will see the output message like below. This means the Jupyter Notebook service has started successfully within the container.

[I 23:51:08.456 NotebookApp] Serving notebooks from local directory: /opt/bigdl-2.1.0-SNAPSHOT/apps
[I 23:51:08.456 NotebookApp] Jupyter Notebook 6.2.0 is running at:
[I 23:51:08.456 NotebookApp] http://xxxx:12345/?token=...
[I 23:51:08.457 NotebookApp]  or http://127.0.0.1:12345/?token=...
[I 23:51:08.457 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).

Then, refer docker guide to open Jupyter Notebook service from a browser and run notebook.

4.4 Run Scala programs

Use spark-submit to submit your BigDL program. e.g., run nnframes imageInference example (running in either local mode or cluster mode) as follows:

${SPARK_HOME}/bin/spark-submit \
  --master ${RUNTIME_SPARK_MASTER} \
  --deploy-mode client \
  --conf spark.driver.host=${RUNTIME_DRIVER_HOST} \
  --conf spark.driver.port=${RUNTIME_DRIVER_PORT} \
  --conf spark.kubernetes.authenticate.driver.serviceAccountName=${RUNTIME_K8S_SERVICE_ACCOUNT} \
  --name bigdl \
  --conf spark.kubernetes.container.image=${RUNTIME_K8S_SPARK_IMAGE} \
  --conf spark.executor.instances=${RUNTIME_EXECUTOR_INSTANCES} \
  --conf spark.kubernetes.driver.volumes.persistentVolumeClaim.${RUNTIME_PERSISTENT_VOLUME_CLAIM}.options.claimName=${RUNTIME_PERSISTENT_VOLUME_CLAIM} \
  --conf spark.kubernetes.driver.volumes.persistentVolumeClaim.${RUNTIME_PERSISTENT_VOLUME_CLAIM}.mount.path=/path \
  --conf spark.kubernetes.executor.volumes.persistentVolumeClaim.${RUNTIME_PERSISTENT_VOLUME_CLAIM}.options.claimName=${RUNTIME_PERSISTENT_VOLUME_CLAIM} \
  --conf spark.kubernetes.executor.volumes.persistentVolumeClaim.${RUNTIME_PERSISTENT_VOLUME_CLAIM}.mount.path=/path \
  --conf spark.kubernetes.driver.label.<your-label>=true \
  --conf spark.kubernetes.executor.label.<your-label>=true \
  --executor-cores ${RUNTIME_EXECUTOR_CORES} \
  --executor-memory ${RUNTIME_EXECUTOR_MEMORY} \
  --total-executor-cores ${RUNTIME_TOTAL_EXECUTOR_CORES} \
  --driver-cores ${RUNTIME_DRIVER_CORES} \
  --driver-memory ${RUNTIME_DRIVER_MEMORY} \
  --properties-file ${BIGDL_HOME}/conf/spark-bigdl.conf \
  --conf spark.driver.extraJavaOptions=-Dderby.stream.error.file=/tmp \
  --conf spark.sql.catalogImplementation='in-memory' \
  --conf spark.driver.extraClassPath=local://${BIGDL_HOME}/jars/*  \
  --conf spark.executor.extraClassPath=local://${BIGDL_HOME}/jars/*  \
  --class com.intel.analytics.bigdl.dllib.examples.nnframes.imageInference.ImageTransferLearning \
  ${BIGDL_HOME}/python/bigdl-spark_${SPARK_VERSION}-${BIGDL_VERSION}-python-api.zip \
  --inputDir /path

Options:

  • –master: the spark mater, must be a URL with the format k8s://https://<k8s-apiserver-host>:<k8s-apiserver-port>.

  • –deploy-mode: submit application in client/cluster mode.

  • –name: the Spark application name.

  • –conf: to specify k8s service account, container image to use for the Spark application, driver volumes name and path, label of pods, spark driver and executor configuration, etc. You can refer to spark configuration and spark on k8s configuration for more details.

  • –properties-file: the customized conf properties.

  • –py-files: the extra python packages is needed.

  • –class: scala example class name.

  • –inputDir: input data path of the nnframe example. The data path is the mounted filesystem of the host. Refer to more details by Kubernetes Volumes.

5 Known Issues

This section shows some common topics for both client mode and cluster mode.

5.1 How to specify the Python environment?

In client mode, follow python user guide to install conda and BigDL and run application:

python script.py

In cluster mode, install conda, pack environment and use on both the driver and executor.

  • Pack the current conda environment to environment.tar.gz (you can use any name you like):

conda pack -o environment.tar.gz
  • spark-submit with “–archives” and specify python stores for dirver and executor

--conf spark.pyspark.driver.python=./env/bin/python \
--conf spark.pyspark.python=./env/bin/python \
--archives local:///bigdl2.0/data/environment.tar.gz#env \ # this path shoud be that k8s pod can access

5.2 How to retain executor logs for debugging?

The k8s would delete the pod once the executor failed in client mode and cluster mode. If you want to get the content of executor log, you could set “temp-dir” to a mounted network file system (NFS) storage to change the log dir to replace the former one. In this case, you may meet JSONDecodeError because multiple executors would write logs to the same physical folder and cause conflicts. The solutions are in the next section.

init_orca_context(..., extra_params = {"temp-dir": "/bigdl/"})

5.3 How to deal with “JSONDecodeError”?

If you set temp-dir to a mounted nfs storage and use multiple executors , you may meet JSONDecodeError since multiple executors would write to the same physical folder and cause conflicts. Do not mount temp-dir to shared storage is one option to avoid conflicts. But if you debug ray on k8s, you need to output logs to a shared storage. In this case, you could set num-nodes to 1. After testing, you can remove temp-dir setting and run multiple executors.

5.4 How to use NFS?

If you want to save some files out of pod’s lifecycle, such as logging callbacks or tensorboard callbacks, you need to set the output dir to a mounted persistent volume dir. Let NFS be a simple example.

Use NFS in client mode:

init_orca_context(cluster_mode="k8s", ...,
                  conf={...,
                  "spark.kubernetes.executor.volumes.persistentVolumeClaim.nfsvolumeclaim.options.claimName":"nfsvolumeclaim",
                  "spark.kubernetes.executor.volumes.persistentVolumeClaim.nfsvolumeclaim.mount.path": "/bigdl" 
                  })

Use NFS in cluster mode:

${SPARK_HOME}/bin/spark-submit \
  --... ...\
  --conf spark.kubernetes.executor.volumes.persistentVolumeClaim.nfsvolumeclaim.options.claimName="nfsvolumeclaim" \
  --conf spark.kubernetes.executor.volumes.persistentVolumeClaim.nfsvolumeclaim.mount.path="/bigdl" \
  --conf spark.kubernetes.driver.volumes.persistentVolumeClaim.nfsvolumeclaim.options.claimName="nfsvolumeclaim" \
  --conf spark.kubernetes.driver.volumes.persistentVolumeClaim.nfsvolumeclaim.mount.path="/bigdl" \
  file:///path/script.py

5.5 How to deal with “RayActorError”?

“RayActorError” may caused by running out of the ray memory. If you meet this error, try to increase the memory for ray.

init_orca_context(..., extra_executor_memory_for_ray="100g")

5.6 How to set proper “steps_per_epoch” and “validation steps”?

The steps_per_epoch and validation_steps should equal to numbers of dataset divided by batch size if you want to train all dataset. The steps_per_epoch and validation_steps do not relate to the num_nodes when total dataset and batch size are fixed. For example, you set num_nodes to 1, and set steps_per_epoch to 6. If you change the num_nodes to 3, the steps_per_epoch should still be 6.

5.7 Others

spark.kubernetes.container.image.pullPolicy needs to be specified as always if you need to update your spark executor image for k8s.

6. Access logs and clear pods

When application is running, it’s possible to stream logs on the driver pod:

$ kubectl logs <spark-driver-pod>

To check pod status or to get some basic information around pod using:

$ kubectl describe pod <spark-driver-pod>

You can also check other pods using the similar way.

After finishing running the application, deleting the driver pod:

$ kubectl delete <spark-driver-pod>

Or clean up the entire spark application by pod label:

$ kubectl delete pod -l <pod label>