Deploy the Database Service

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What Knative features will we learn about?

  • What is a good usecase to use Knative Service

What does the final deliverable look like?

  • Running a PostgreSQL StatefulSet that contains the table and some sample data

Concept Learning

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Knative Services are a powerful feature within the Knative ecosystem, designed to handle a wide range of use cases, especially in modern cloud-native applications, it can be controlled by Knative Serving, and achieve scale to 0. Here’s an expanded explanation of when and why you should consider using Knative Services:

Stateless Workloads

  • Definition: Stateless applications do not store any data locally between requests. Each request is independent and does not rely on any previous interaction.
  • Use Case: Examples include web servers, APIs, and microservices where the state is managed externally, such as in a database or a cache.
  • Benefits: Simplifies scaling and failover because any instance can handle any request without requiring session persistence.

Event-Driven Workloads

  • Definition: Event-driven architectures respond to events or Triggers, such as HTTP requests, messages in a queue, or changes in a database.
  • Use Case: Use Knative Services to deploy functions that react to events, such as processing incoming data, triggering workflows, or integrating with third-party APIs.
  • Benefits: Efficient resource utilization, as services can scale down to zero when not handling events, reducing costs and improving performance.

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Try to ask in the Knative Slack community #knative whether it is the best use case or not.

Implementation

Step 1: apply all the config yaml files

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In this section, we will just be simply running a PostgreSQL service. We have all config files ready. Simply run the following command to apply all yamls at once.

  1. kubectl apply -f db-service

Warning

Please wait few minutes until everything become ready. If you see some job pods are failing and having errors, that’s okay. Just continue waiting.

Verify

You should see the following output:

  1. configmap/sql-configmap created
  2. secret/postgresql-secret created
  3. persistentvolumeclaim/postgresql-pvc created
  4. statefulset.apps/postgresql created
  5. service/postgresql created
  6. job.batch/postgresql-job created

Wait a moment until all the pods become available and the database migration job is completed. If you see some job pods are failing and having errors, don’t worry, please wait until at least one job becomes “Completed“.

  1. NAME                                  READY   STATUS    RESTARTS   AGE
  2. bookstore-frontend-7b879ffb78-9bln6   1/1     Running   0          6h53m
  3. camel-k-operator-7989475884-7wk6z     1/1     Running   0          5h26m
  4. event-display-55967c745d-bxrgh        1/1     Running   0          5h26m
  5. node-server-644795d698-r9zlr          1/1     Running   0          5h26m
  6. postgresql-0                          1/1     Running   0          5h23m
  7. postgresql-job-55dlv                  0/1     Completed 0          10s
  8. postgresql-job-fnv8m                  0/1     Error     0          73s

Verification

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Open the UI page at http://localhost:3000, you should see some new comments popping up at the bottom of the page.

Troubleshoot

If you see “No comments available”, that means your database is not initialized yet. Check the health of the database service pods and figure out what happened.

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Next Step

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You have successfully set up the database services, and it is ready to receive requests and store user comments.

Next, we’ll complete our event-driven architecture by connecting all the components you created. This is where the magic happens.

Go to Implement Advanced Event Filtering 5 - Create DB service - 图8