On-Prem Airflow Storage Setup | OpenMetadata Kubernetes Guide

Provision NFS-backed persistent volumes for Airflow DAGs and logs on on-premises Kubernetes and deploy OpenMetadata.

On-Prem Airflow Storage Setup

This guide walks through provisioning NFS-backed PVCs for Airflow DAGs and logs on an on-premises Kubernetes cluster, then deploying OpenMetadata. For prerequisites and StorageClass setup, see the On-Prem Kubernetes Deployment page.

Provision NFS backed PVC for Airflow DAGs and Airflow Logs

Code Samples for PVC for Airflow DAGs

# dags_pvc.yml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  namespace: default
  name: openmetadata-dependencies-dags
  labels:
    storage.k8s.io/name: nfs
    app: airflow
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: nfs-client
  resources:
    requests:
      storage: 1Gi

Create Persistent Volumes and Persistent Volume claims with the below command.

kubectl create -f dags_pvc.yml

Code Samples for PVC for Airflow Logs

# logs_pvc.yml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  namespace: default
  name: openmetadata-dependencies-logs
  labels:
    storage.k8s.io/name: nfs
    app: airflow
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: nfs-client
  resources:
    requests:
      storage: 10Gi

Create Persistent Volumes and Persistent Volume claims with the below command.

kubectl create -f logs_pvc.yml

Change owner and permission manually on disks

Since airflow pods run as non-root users, they would not have write access on the nfs server volumes. In order to fix the permission here, spin up a pod with persistent volumes attached and run it once.

# permissions_pod.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: my-permission-pod
  name: my-permission-pod
spec:
  containers:
  - image: busybox
    name: my-permission-pod
    volumeMounts:
    - name: airflow-dags
      mountPath: /airflow-dags
    - name: airflow-logs
      mountPath: /airflow-logs
    command:
    - "chown -R 50000 /airflow-dags /airflow-logs"
    # if needed
    - "chmod -R a+rwx /airflow-dags"
  volumes:
  - name: airflow-logs
    persistentVolumeClaim:
      claimName: openmetadata-dependencies-logs
  - name: airflow-dags
    persistentVolumeClaim:
      claimName: openmetadata-dependencies-dags
  dnsPolicy: ClusterFirst
  restartPolicy: Always

Airflow runs the pods with linux username as airflow and linux user id as 50000.

Run the below command to create the pod and fix the permissions

kubectl create -f permissions_pod.yml

Create OpenMetadata dependencies Values

Override openmetadata dependencies airflow helm values to bind the nfs persistent volumes for DAGs and logs.

# values-dependencies.yml
airflow:
  airflow:
    extraVolumeMounts:
      - mountPath: /airflow-logs
        name: nfs-airflow-logs
      - mountPath: /airflow-dags/dags
        name: nfs-airflow-dags
    extraVolumes:
      - name: nfs-airflow-logs
        persistentVolumeClaim:
          claimName: openmetadata-dependencies-logs
      - name: nfs-airflow-dags
        persistentVolumeClaim:
          claimName: openmetadata-dependencies-dags
    config:
      AIRFLOW__OPENMETADATA_AIRFLOW_APIS__DAG_GENERATED_CONFIGS: "/airflow-dags/dags"
  dags:
    path: /airflow-dags/dags
    persistence:
      enabled: false
  logs:
    path: /airflow-logs
    persistence:
      enabled: false

For more information on airflow helm chart values, please refer to airflow-helm.

When deploying openmetadata dependencies helm chart, use the below command -

helm install openmetadata-dependencies open-metadata/openmetadata-dependencies --values values-dependencies.yaml

The above command uses configurations defined here. You can modify any configuration and deploy by passing your own values.yaml

helm install openmetadata-dependencies open-metadata/openmetadata-dependencies --values <path-to-values-file>

Once the openmetadata dependencies helm chart deployed, you can then run the below command to install the openmetadata helm chart -

helm install openmetadata open-metadata/openmetadata

Again, this uses the values defined here. Use the --values flag to point to your own YAML configuration if needed.

Troubleshooting

Starting with OpenMetadata v1.12.4, the dependency Helm chart no longer supports passing database passwords using individual Kubernetes secret keys (for example, passwordSecret and passwordSecretKey).

Instead, database credentials must be provided via a single Kubernetes Secret referenced using metadataSecretName. This secret must contain the full database connection string, including the password.

data:
  metadataSecretName: your-connection-string-secret

This change applies only to the dependency values.yml configuration and aligns with the database configuration approach used by the Airflow Helm chart.

FAQs

Java Memory Heap Issue

If your openmetadata pods are not in ready state at any point in time and the openmetadata pod logs speaks about the below issue -

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "AsyncAppender-Worker-async-file-appender"
Exception in thread "pool-5-thread-1" java.lang.OutOfMemoryError: Java heap space
Exception in thread "AsyncAppender-Worker-async-file-appender" java.lang.OutOfMemoryError: Java heap space
Exception in thread "dw-46" java.lang.OutOfMemoryError: Java heap space
Exception in thread "AsyncAppender-Worker-async-console-appender" java.lang.OutOfMemoryError: Java heap space

This is due to the default JVM Heap Space configuration (1 GiB) being not enough for your workloads. In order to resolve this issue, head over to your custom openmetadata helm values and append the below environment variable

extraEnvs:
- name: OPENMETADATA_HEAP_OPTS
  value: "-Xmx2G -Xms2G"

The flag Xmx specifies the maximum memory allocation pool for a Java virtual machine (JVM), while Xms specifies the initial memory allocation pool.

Upgrade the helm charts with the above changes using the following command helm upgrade --install openmetadata open-metadata/openmetadata --values <values.yml> --namespace <namespaceName>. Update this command your values.yml filename and namespaceName where you have deployed OpenMetadata in Kubernetes.

PostgreSQL Issue permission denied to create extension “pgcrypto”

If you are facing the below issue with PostgreSQL as Database Backend for OpenMetadata Application,

Message: ERROR: permission denied to create extension "pgcrypto"
Hint: Must be superuser to create this extension.

It seems the Database User does not have sufficient privileges. In order to resolve the above issue, grant usage permissions to the PSQL User.

GRANT USAGE ON SCHEMA schema_name TO <openmetadata_psql_user>;
GRANT CREATE ON EXTENSION pgcrypto TO <openmetadata_psql_user>;

In the above command, replace <openmetadata_psql_user> with the sql user used by OpenMetadata Application to connect to PostgreSQL Database.

How to extend and use custom docker images with OpenMetadata Helm Charts ?

Extending OpenMetadata Server Docker Image

1. Create a Dockerfile based on docker.open-metadata.org/openmetadata/server

OpenMetadata helm charts uses official published docker images from DockerHub. A typical scenario will be to install organization certificates for connecting with inhouse systems.

For Example -

FROM docker.open-metadata.org/openmetadata/server:x.y.z
WORKDIR /home/
COPY <my-organization-certs> .
RUN update-ca-certificates

where docker.open-metadata.org/openmetadata/server:x.y.z needs to point to the same version of the OpenMetadata server, for example docker.open-metadata.org/openmetadata/server:1.3.1. This image needs to be built and published to the container registry of your choice.

2. Update your openmetadata helm values yaml

The OpenMetadata Application gets installed as part of openmetadata helm chart. In this step, update the custom helm values using YAML file to point the image created in the previous step. For example, create a helm values file named values.yaml with the following contents -

...
image:
  repository: <your repository>
  # Overrides the image tag whose default is the chart appVersion.
  tag: <your tag>
...

3. Install / Upgrade your helm release

Upgrade/Install your openmetadata helm charts with the below single command:

helm upgrade --install openmetadata open-metadata/openmetadata--values values.yaml

Extending OpenMetadata Ingestion Docker Image

One possible use case where you would need to use a custom image for the ingestion is because you have developed your own custom connectors. You can find a complete working example of this here. After you have your code ready, the steps would be the following:

1. Create a Dockerfile based on docker.open-metadata.org/openmetadata/ingestion:

For example -

FROM docker.open-metadata.org/openmetadata/ingestion:x.y.z

USER airflow
# Let's use the home directory of airflow user
WORKDIR /home/airflow

# Install our custom connector
COPY <your_package> <your_package>
COPY setup.py .
RUN pip install --no-deps .

where docker.open-metadata.org/openmetadata/ingestion:x.y.z needs to point to the same version of the OpenMetadata server, for example docker.open-metadata.org/openmetadata/ingestion:1.3.1. This image needs to be built and published to the container registry of your choice.

2. Update the airflow in openmetadata dependencies values YAML

The ingestion containers (which is the one shipping Airflow) gets installed in the openmetadata-dependencies helm chart. In this step, we use our own custom values YAML file to point to the image we just created on the previous step. You can create a file named values.deps.yaml with the following contents:

airflow:
  airflow:
    image:
      repository: <your repository>  # by default, openmetadata/ingestion
      tag: <your tag>  # by default, the version you are deploying, e.g., 1.1.0
      pullPolicy: "IfNotPresent"

3. Install / Upgrade helm release

Upgrade/Install your openmetadata-dependencies helm charts with the below single command:

helm upgrade --install openmetadata-dependencies open-metadata/openmetadata-dependencies --values values.deps.yaml

How to disable MySQL and ElasticSearch from OpenMetadata Dependencies Helm Charts ?

If you are using MySQL and ElasticSearch externally, you would want to disable the local installation of mysql and elasticsearch while installing OpenMetadata Dependencies Helm Chart. You can disable the MySQL and ElasticSearch Helm Dependencies by setting enabled: false value for each dependency. Below is the command to set helm values from Helm CLI -

helm upgrade --install openmetadata-dependencies open-metadata/openmetadata-dependencies --set mysql.enabled=false --set elasticsearch.enabled=false

Alternatively, you can create a custom YAML file named values.deps.yaml to disable installation of MySQL and Elasticsearch .

mysql:
    enabled: false
    ...
elasticsearch:
    enabled: false
    ...
...

How to configure external database like PostgreSQL with OpenMetadata Helm Charts ?

OpenMetadata Supports PostgreSQL as one of the Database Dependencies. OpenMetadata Helm Charts by default does not include PostgreSQL as Database Dependencies. In order to configure Helm Charts with External Database like PostgreSQL, follow the below guide to make the helm values change and upgrade / install OpenMetadata helm charts with the same.

Upgrade Airflow Helm Dependencies Helm Charts to connect to External Database like PostgreSQL

We ship airflow-helm as one of OpenMetadata Dependencies with default values to connect to MySQL Database as part of externalDatabase configurations.

You can find more information on setting the externalDatabase as part of helm values here.

With OpenMetadata Dependencies Helm Charts, your helm values would look something like below -

...
airflow:
  externalDatabase:
    type: postgresql
    host: <postgresql_endpoint>
    port: 5432
    database: <airflow_database_name>
    user: <airflow_database_login_user>
    passwordSecret: airflow-postgresql-secrets
    passwordSecretKey: airflow-postgresql-password
...

For the above code, it is assumed you are creating a kubernetes secret for storing Airflow Database login Credentials. A sample command to create the secret will be kubectl create secret generic airflow-postgresql-secrets --from-literal=airflow-postgresql-password=<password>.

Upgrade OpenMetadata Helm Charts to connect to External Database like PostgreSQL

Update the openmetadata.config.database.* helm values for OpenMetadata Application to connect to External Database like PostgreSQL.

With OpenMetadata Helm Charts, your helm values would look something like below -

openmetadata:
  config:
    ...
    database:
      host: <postgresql_endpoint>
      port: 5432
      driverClass: org.postgresql.Driver
      dbScheme: postgresql
      dbUseSSL: true
      databaseName: <openmetadata_database_name>
      auth:
        username: <database_login_user>
        password:
          secretRef: openmetadata-postgresql-secrets
          secretKey: openmetadata-postgresql-password

For the above code, it is assumed you are creating a kubernetes secret for storing OpenMetadata Database login Credentials. A sample command to create the secret will be kubectl create secret generic openmetadata-postgresql-secrets --from-literal=openmetadata-postgresql-password=<password>.

Once you make the above changes to your helm values, run the below command to install/upgrade helm charts -

helm upgrade --install openmetadata-dependencies open-metadata/openmetadata-dependencies --values <<path-to-values-file>> --namespace <kubernetes_namespace>
helm upgrade --install openmetadata open-metadata/openmetadata --values <<path-to-values-file>> --namespace <kubernetes_namespace>

How to customize OpenMetadata Dependencies Helm Chart with custom helm values

Our OpenMetadata Dependencies Helm Charts are internally depends on three sub-charts -

• Bitnami MySQL (helm chart version 9.7.2)
• OpenSearch (helm chart version 2.12.2)
• Airflow (helm chart version 8.8.0)

If you are looking to customize the deployments of any of the above dependencies, please refer to the above links for customizations of helm values for further references.

By default, OpenMetadata Dependencies helm chart provides initial generic customization of these helm values in order to get you started quickly. You can refer to the openmetadata-dependencies helm charts default values here.