Deploy the Database Service¶
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¶
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.
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¶
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.
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:
configmap/sql-configmap created
secret/postgresql-secret created
persistentvolumeclaim/postgresql-pvc created
statefulset.apps/postgresql created
service/postgresql created
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".
NAME READY STATUS RESTARTS AGE
bookstore-frontend-7b879ffb78-9bln6 1/1 Running 0 6h53m
camel-k-operator-7989475884-7wk6z 1/1 Running 0 5h26m
event-display-55967c745d-bxrgh 1/1 Running 0 5h26m
node-server-644795d698-r9zlr 1/1 Running 0 5h26m
postgresql-0 1/1 Running 0 5h23m
postgresql-job-55dlv 0/1 Completed 0 10s
postgresql-job-fnv8m 0/1 Error 0 73s
Verification¶
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.
Next Step¶
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.