EventTrigger CRD

The EventTrigger custom resource definition (CRD) runs a task when the condition of a Kubernetes object changes to a specified status. EventTrigger extends the Kubernetes Job, a workload resource that creates pods, runs a task, then cleans up the pods after the task completes.

Prerequisites

• Deploy a VerticaDB operator.
• Confirm that you have the resources to deploy objects you plan to create.

Limitations

The EventTrigger CRD has the following limitations:

• It can monitor a condition status on only one VerticaDB custom resource (CR).
• You can match only one condition status.
• The EventTrigger and the object that it watches must exist within the same namespace.

Creating an EventTrigger

An EventTrigger resource defines the Kubernetes object that you want to watch, the status condition that triggers the Job, and a pod template that contains the Job logic and provides resources to complete the Job.

This example creates a YAML-formatted file named eventtrigger.yaml. When you apply eventtrigger.yaml to your VerticaDB CR, it creates a single-column database table when the VerticaDB CR's DBInitialized condition status changes to True:

$ kubectl describe vdb verticadb-name
Status:
 ...
  Conditions:
    ...
    Last Transition Time:   transition-time
    Status:                 True 
    Type:                   DBInitialized

The following fields form the spec, which defines the desired state of the EventTrigger object:

• references: The Kubernetes object whose condition status you want to watch.
• matches: The condition and status that trigger the Job.
• template: Specification for the pods that run the Job after the condition status triggers an event.

The following steps create an EventTrigger CR:

1. Add the apiVersion, kind, and metadata.name required fields:

   apiVersion: vertica.com/v1beta1
   kind: EventTrigger
   metadata:
       name: eventtrigger-example
   

2. Begin the spec definition with the references field. The object field is an array whose values identify the VerticaDB CR object that you want to watch. You must provide the VerticaDB CR's apiVersion, kind, and name:

   spec:
     references:
     - object:
         apiVersion: vertica.com/v1beta1
         kind: VerticaDB
         name: verticadb-example
   

3. Define the matches field that triggers the Job. EventTrigger can match only one condition:

   spec:
     ...
     matches:
     - condition:
         type: DBInitialized
         status: "True"
   

   The preceding example defines the following:

   • condition.type: The condition that the operator watches for state change.
   • condition.status: The status that triggers the Job.

4. Add the template that defines the pod specifications that run the Job after matches.condition triggers an event.

   A pod template requires its own spec definition, and it can optionally have its own metadata. The following example includes metadata.generateName, which instructs the operator to generate a unique, random name for any pods that it creates for the Job. The trailing dash (-) separates the user-provided portion from the generated portion:

   spec:
     ...
     template:
       metadata:
         generateName: create-user-table-
       spec:
         template:
           spec:
             restartPolicy: OnFailure
             containers:
             - name: main
               image: "vertica/vertica-k8s:latest"
               command: ["/opt/vertica/bin/vsql", "-h", "verticadb-sample-defaultsubcluster", "-f", "CREATE TABLE T1 (C1 INT);"]
   

   The remainder of the spec defines the following:

   • restartPolicy: When to restart all containers in the pod.
   • containers: The containers that run the Job.
     • name: The name of the container.
     • image: The image that the container runs.
     • command: An array that contains a command, where each element in the array combines to form a command. The final element creates the single-column SQL table.

Apply the manifest

After you create the EventTrigger, apply the manifest in the same namespace as the VerticaDB CR:

$ kubectl apply -f eventtrigger.yaml

eventtrigger.vertica.com/eventtrigger-example created
configmap/create-user-table-sql created

After you create the database, the operator runs a Job that creates a table. You can check the status with kubectl get job:

$ kubectl get job
NAME                COMPLETIONS   DURATION   AGE
create-user-table   1/1           4s         7s

Verify that the table was created in the logs:

$ kubectl logs create-user-table-guid
CREATE TABLE

Complete file reference

apiVersion: vertica.com/v1beta1
kind: EventTrigger
metadata:
    name: eventtrigger-example
spec:
  references:
  - object:
      apiVersion: vertica.com/v1beta1
      kind: VerticaDB
      name: verticadb-example
  matches:
  - condition:
      type: DBInitialized
      status: "True"
  template:
    metadata:
      generateName: create-user-table-
    spec:
      template:
        spec:
          restartPolicy: OnFailure
          containers:
          - name: main
            image: "vertica/vertica-k8s:latest"
            command: ["/opt/vertica/bin/vsql", "-h", "verticadb-sample-defaultsubcluster", "-f", "CREATE TABLE T1 (C1 INT);"]

Monitoring an EventTrigger

The following table describes the status fields that help you monitor an EventTrigger CR: