Labels
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Basic workflow of creating replicas
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As k8s is used and application microservices run in the cluster, number of pods running of nodes might grow in size and complexity.
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K8s has added foundational concepts of Labels and annotations to organization, mark and cross-index all of your resources to represent the groups.
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Labels are key/value pairs that can be attached to k8s objects such as pods and ReplicaSets. Labels are used by k8s cluster to group pods/other objects
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_Annotations provide storage mechanism similar to labels which information that can be used by tools & libraries
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Labels provide identifying metadata
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Refer Here for the changeset created with labels
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Lets create one more replicaset with jenkins running in it Refer Here
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Pods can be selected by writing selectors
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Some selector examples
---
selector:
matchLabels:
app: jenkins
---
selector:
matchExpressions:
- {key: app, operator: In, values: ['jenkins', 'gol']}
---
selector:
matchExpressions:
- {key: ver, operator: NotIn, values: ['1.0', '2.0']}
- If you want to all the api-resources in k8s cluster
kubectl api-resources
Service Discovery
- We are able to run our applications in pods
- We can dynamically scale pods by using autoscale command
- How do i access my application which is running in pods
- Service-discovery helps solving the problem of finding which processses are listening at which address for each service.
- We need to expose our services to the external world. As of now w.r.t networking we know each pod is having its own ip address.
- Excercise: Ensure you go through
- Single host docker networking
- Multi host docker networking.
- Ensure you have atleast AWS/Azure free account created.
