# 10. K8 Services
### Service
* Each pod has its own IP address
* Pods are ephemeral - destoryed frequently
* Service gives stable IP address
* Provides load balancing
***
### Types
#### 1. ClusterIP
* default type
* pod gets ip address from node's range
**How Service Knows which Pod to Forward Request to**
**How Service Knows which Port to Forward Request to**
**Service Endpoints**
* K8 create endpoints object
* have same name as service
* keeps track of which pods are members/endpoint of the service
**Multiple Ports Service**
#### 2. Headless Service
* clients want to communicate with 1 specific pod directly
* pod wants to talk directly with specific pod not a randomly selected pod
* Use Case: Stateful applications like databases
* pod replicas are not identical
* Client needs to figure out IP address of each pod
* Option 1 - API call to K8 API Server (X)
* Option 2 - DNS Lookup (Recommended)
* DNS lookup for service - returns single ip address
* If ClusterIP is set to None - returns pod ip address instead
*
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***
### Service Type Attributes
1. ClusterIP
* Only accessible within cluster
2. NodePort
* extension of clusterip service
* External traffic has access to fixed port on each worker node
*
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*
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* not secure and efficient since port is directly accessible externally
* not used in production environments
3. Load Balancer
* extension of nodeport service
* becomes accessible externally through cloud provider loadbalancers
*
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* secure and efficient since port is not accessible directly but via load balancer
* used in production environments
***
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