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Operatorless Mode

Operatorless Mode


It's possible to have the basic functionality of SchemaHero, without running the in-cluster operator. This option makes it possible to run SchemaHero in environments that do not have Kubernetes. This is useful when shipping software on-prem (such as with KOTS), and you don't want to require cluster-admin level permissions that are necessary to install a CustomResourceDefinition.

Missing Features

When running SchemaHero without the in-cluster operator, there will won't be seperate plan and apply phases. Changes made and submitted will be applied automatically. Additionally, the kubectl plugin will not work without the operator, including the kubectl schemahero shell command.

Running Without the Operator

To do this, you'll build a new Docker image using the SchemaHero image as the base image. This Docker image will be the image used in a Kubernetes Job. The Job will contain an initContainer to execute the plan phase and a container to apply. There is no elevated access required, and this method does not rely on any external resources such as PersistentVolumeClaims.

An example of the required Dockerfile is:

FROM schemahero/schemahero:0.10.4
ADD --chown=schemahero:schemahero ./tables ./tables

And the required Kubernetes Job manifest to run these migrations:

apiVersion: batch/v1
kind: Job
metadata:
  name: my-migrations
  annotations:
    "kots.io/hook-delete-policy": "hook-succeeded, hook-failed"
spec:
  template:
    spec:
      volumes:
        - name: migrations
          emptyDir:
            medium: Memory
      restartPolicy: OnFailure
      initContainers:
        - image: my-migrations-image
          name: migrations-plan
          volumeMounts:
            - name: migrations
              mountPath: /migrations
          args: ["plan"]
          env:
            - name: SCHEMAHERO_DRIVER
              value: postgres
            - name: SCHEMAHERO_SPEC_FILE
              value: /tables
            - name: SCHEMAHERO_OUT
              value: /migrations/plan.yaml
            - name: SCHEMAHERO_URI
              valueFrom:
                secretKeyRef:
                  name: my-postgres-secret
                  key: uri
      containers:
        - image: my-migrations-image
          name: migrations-apply
          volumeMounts:
            - name: migrations
              mountPath: /migrations
          args: ["apply"]
          env:
            - name: SCHEMAHERO_DRIVER
              value: postgres
            - name: SCHEMAHERO_DDL
              value: /migrations/plan.yaml
            - name: SCHEMAHERO_URI
              valueFrom:
                secretKeyRef:
                  name: my-postgres-secret
                  key: uri
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