Exercise 1: Create a Pod Manifest to run alpine with sleep 1d
- Refer Here for the changes made
- Now lets look at describing out
kubectl describe <resource-name> <object-name>
Using Port forwarding
- Lets launch the pod from activity1
Getting More Information With Logs
Activity 3: Create a Pod with container which has CMD to get container to exited state
- Refer Here for the changes
- As the container gets into the exited state pod tries to restart the container and this happens continuously
- To deal with these kind of continuous restarts we will be learning probes.
Activity 4: Start activity 1
- create a pod with spec activity1.yaml
- Now shutdown the node where activity1 is running. (Simulating some error on the node)
- Node is shutdown, Pod is not accesible, but k8s is not scheduling this pod to run on other node
Workload Resources
- Kubernetes Provides different workload resources
- Replicaset:
- This is used to create multiple replications of your Pod which is running your application
- Deployment
- Statefulset
- DaemonSet
- Job and CronJob
- If we try to use the above workloads then the desired state is maintained
- Since Pod cannot maintain its own state i.e. if the Pod is Down, schedule the Pod on a new node
- Running our application in the Workload resources which maintain some kind of desired state is what we want.
- Before we understand workload resources, we need to understand the concept of labels and annotations in kubernetes
Labels
- Labels are key/value pairs that can be attached to k8s objects such as Pods, replicasets etc.
- They are arbitrary and are useful for identifying information about k8s objects
- They provide the foundation for grouping objects
- Labels have very simple syntax.
- Keys can be broken down into two parts an optional prefix and a name seperated by slahs (dots, underscores, dashes(hypens)) can be used in names
- Values are strings with maximum of 63 characters
- Examples:
| key | value |
| — | ——|
| qt.com/app-version | 1.0.0 |
| appVersion | 1.0.0 |
| app.version | 1.0.0 |
| project | qtidentitiy |
* Lets try to apply labels
* Now lets get labels
* Label Selectors: These are used to filter k8s objects based on set of labels
* Lets create labels in the declarative approach. Refer Here for the Pod manifest
* Selectors in the Yaml will be in the format of
selector:
app: web
env: prod
Annotations
- Annotations are also key value pairs like labels which provide a place to store additional metadata for k8s objects with the sole purpose of assisting tools and libraries
metadata:
annotations:
qt.com/icons-url: "https://qt.com/icon-main.png"
ReplicaSets
- If we want multiple replicas of the application in Pod running and maintaing the state of number of replicas we use replica sets
Activity 5: Lets create a replicaset to create 2 replicas of jenkins (Pod)
- Refer Here for api reference
- Refer Here for Replicaset Spec
- Refer Here for the ReplicaSet Manifest created
- Now delete one pod manually to see what replica set does
