LoadBalancer service type in Kubernetes - Step-by-Step Execution

Process Flow - LoadBalancer service type

Create Service YAML with type LoadBalancer

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kubectl apply -f service.yaml

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Kubernetes requests cloud provider

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Cloud provider provisions external LoadBalancer

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External IP assigned to Service

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Clients access Service via External IP

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LoadBalancer forwards traffic to Pods

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Service works

This flow shows how creating a LoadBalancer service in Kubernetes triggers cloud provider actions to expose the service externally.

Execution Sample

Kubernetes

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  type: LoadBalancer
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080

This YAML defines a LoadBalancer service exposing pods with label app=my-app on port 80 externally.

Process Table

Step	Action	Kubernetes State	Cloud Provider Action	Result
1	Apply service YAML	Service object created with type LoadBalancer	None yet	Service pending external IP
2	Kubernetes requests cloud provider	Service status pending	Provision external LoadBalancer	LoadBalancer resource created
3	Cloud provider creates LoadBalancer	Service status updating	Assign external IP	External IP assigned to Service
4	Service ready	Service has external IP	LoadBalancer forwards traffic	Clients can access service externally
5	Client sends request	Request received by LoadBalancer	Forward to pod endpoints	Pods receive traffic
6	Pods respond	Response sent back through LoadBalancer	Response forwarded to client	Client receives response
7	End	Service running with external IP	LoadBalancer active	Operation complete

💡 Service has external IP and traffic flows through LoadBalancer to pods

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Service Object	None	Created with type LoadBalancer	Pending external IP	External IP assigned	Ready with external IP
External IP	None	None	None	Assigned (e.g. 34.68.12.34)	Assigned (e.g. 34.68.12.34)
LoadBalancer Status	None	None	Provisioning	Active	Active

Key Moments - 3 Insights

Why does the Service not have an external IP immediately after creation?

Because Kubernetes must first request the cloud provider to create the LoadBalancer, which takes time. See execution_table step 2 and 3 where the external IP is assigned only after provisioning.

What happens if the cloud provider does not support LoadBalancer services?

The Service will remain without an external IP and stay in pending state. This is shown in execution_table step 2 where the cloud provider action is required but may not happen.

How does traffic reach the pods from the external IP?

The LoadBalancer forwards incoming traffic to the pods selected by the Service selector. This is shown in execution_table steps 5 and 6.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the external IP assigned to the Service?

A Step 3

B Step 5

C Step 1

D Step 7

💡 Hint

Check the 'External IP assigned to Service' result in the rows.

According to variable_tracker, what is the state of the Service Object after Step 2?

A External IP assigned

B Created with type LoadBalancer

C Pending external IP

D Ready with external IP

💡 Hint

Look at the 'Service Object' row under 'After Step 2' column.

If the cloud provider fails to provision the LoadBalancer, what will happen to the Service status?

A Service will have an external IP

B Service will remain pending without external IP

C Service will be deleted automatically

D Service will switch to ClusterIP type

💡 Hint

Refer to key_moments about cloud provider support and execution_table step 2.

Concept Snapshot

LoadBalancer Service in Kubernetes:
- type: LoadBalancer exposes service externally
- Kubernetes requests cloud provider to create LoadBalancer
- External IP assigned after provisioning
- Traffic flows from external IP to pods
- Requires cloud provider support

Full Transcript

This visual execution shows how a Kubernetes Service of type LoadBalancer works. First, you create a Service YAML with type LoadBalancer and apply it. Kubernetes then asks the cloud provider to create an external LoadBalancer. The cloud provider provisions it and assigns an external IP to the Service. Clients can then access the Service using this external IP. The LoadBalancer forwards traffic to the pods selected by the Service. The execution table traces each step from creation to traffic flow. The variable tracker shows how the Service object and external IP change state. Key moments clarify common confusions like why the external IP is not immediate and what happens if the cloud provider does not support LoadBalancer. The quiz tests understanding of when the external IP is assigned and the Service status during provisioning.