Operator SDK basics in Kubernetes - Step-by-Step Execution

Process Flow - Operator SDK basics

Start: Create Operator Project

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Define API & Controller

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Build Operator Binary

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Deploy Operator to Cluster

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Operator Watches Resources

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Reconcile Loop Executes

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Update Cluster State

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End

This flow shows the main steps in using Operator SDK: create project, define API, build, deploy, watch resources, reconcile, and update cluster.

Execution Sample

Kubernetes

operator-sdk init --domain=example.com --repo=github.com/example/memcached-operator
operator-sdk create api --group=cache --version=v1 --kind=Memcached
make install
make run

This sequence initializes an operator project, creates an API for Memcached, installs CRDs, and runs the operator locally.

Process Table

Step	Command/Action	Effect	Output/Result
1	operator-sdk init --domain=example.com --repo=github.com/example/memcached-operator	Creates operator project structure	Project scaffold created with Go modules and config files
2	operator-sdk create api --group=cache --version=v1 --kind=Memcached	Generates API and controller files	API types and controller skeleton generated
3	make install	Installs CRDs to cluster	CRDs installed, cluster ready to recognize Memcached resources
4	make run	Runs operator locally	Operator starts, watches Memcached resources, logs events
5	Create Memcached CR in cluster	Triggers reconcile loop	Operator detects new resource and acts accordingly
6	Operator updates cluster state	Creates/updates pods or services	Memcached pods deployed or updated
7	Operator continues watching	Reconciles on changes	Cluster state stays in desired condition
8	Exit	Stop operator	Operator process ends

💡 Operator stops when user interrupts or process ends

Status Tracker

Variable	Start	After Step 2	After Step 4	After Step 6	Final
Project Files	None	API and controller files created	Operator binary ready	Operator running and watching	Operator stopped
Cluster State	No CRDs	CRDs installed	No Memcached resources	Memcached pods created	Pods running as expected
Operator Status	Not running	Not running	Running	Reconciling	Stopped

Key Moments - 3 Insights

Why do we run 'make install' before running the operator?

Because 'make install' installs the Custom Resource Definitions (CRDs) into the cluster, so the cluster knows about the new resource types the operator manages. Without this, the operator cannot watch or manage those resources (see execution_table step 3).

What happens when we create a Memcached custom resource in the cluster?

The operator detects the new resource and triggers the reconcile loop to create or update the necessary pods or services to match the desired state (see execution_table step 5 and 6).

Why does the operator keep running after deploying resources?

Because it continuously watches for changes in the resources it manages and reconciles the cluster state to keep it as desired (see execution_table step 7).

Visual Quiz - 3 Questions

Look at the execution table, what is the effect of the 'operator-sdk create api' command at step 2?

A Installs CRDs to cluster

B Generates API and controller files

C Runs the operator locally

D Creates operator project structure

💡 Hint

Check the 'Effect' column in execution_table row 2

At which step does the operator start watching Memcached resources?

A Step 3

B Step 5

C Step 4

D Step 6

💡 Hint

Look at the 'Output/Result' column in execution_table step 4

If we skip 'make install', what will happen when we run the operator?

A Operator will fail to recognize custom resources

B Operator will run normally and manage resources

C Operator will create CRDs automatically

D Operator will install CRDs during runtime

💡 Hint

Refer to key_moments explanation about 'make install' and execution_table step 3

Concept Snapshot

Operator SDK basics:
- Use 'operator-sdk init' to start a project
- 'operator-sdk create api' generates API and controller
- 'make install' installs CRDs to cluster
- 'make run' runs operator locally
- Operator watches custom resources and reconciles
- Keeps cluster state as desired continuously

Full Transcript

The Operator SDK basics start with creating a new operator project using 'operator-sdk init'. Then, you generate the API and controller code with 'operator-sdk create api'. Next, you install the Custom Resource Definitions (CRDs) into your Kubernetes cluster using 'make install' so the cluster understands your new resource types. After that, you run the operator locally with 'make run', which starts watching for your custom resources. When you create a custom resource like Memcached, the operator detects it and runs the reconcile loop to update the cluster state, such as creating pods. The operator keeps running to watch for changes and maintain the desired state. You stop the operator when you want to end the process.