Deployment Strategies

When it comes to changing the version of the software (i.e. your application), a K8s deployment supports two strategies
Recreate
RollingUpdate

Recreate Strategy

This strategy updates the replica set and terminates all of the Pods associated with deployment.
The ReplicaSet noticias that it no longer has any replicase and re-creates all the Pods using new Image.
Once the Pods are recreated, they are running the new version.
While this strategy is simple and fast, it has one major drawback, it leads to certain downtime of your application.

This strategy is generally preferable strategy for any user facing service.
While it is slower than Recreate, the Rolling Update can rollout a new version of your service while it serving usertraffic, without having any downtime.
Configure: There are two Parameters that can be used to tune the rolling update behavior
maxUnavailable:
- this parameter sets the maximum number of Pods that can be unavailable during a rolling update
- It can be either set to an absolute (2) or percent (25%)
maxSurge:
- This parameter controls how many extra resources can be created to acheive a rollout.
- It can be either set to an absolute (2) or percent (25%)
Refer Here for the yaml spec with maxSurge and maxUnavailable
Create a deployment
Create a Service
Lets create a new version and see how the deployment Refer Here

I want to replicate Set of Pods where i want to have exactly one Pod on every Node in the cluster because this pod is my log agent
A Daemonset ensures a copy of Pod is running across a set of nodes in the k8s cluster.
As an example lets try to create a daemonset which runs an alpine container with sleep 1d
Refer Here for the changes done

While long-running processes make up the large majority of workloads that are run in k8s cluster, there is often a need for short-lived one-off tasks.
A K8S Job Object is made for handling these type of tasks
A job creates a pod that run until succesful termination.
A regular Pod will continually restart the container regardless of exit code.
Jobs are useful for things you only want to do once, such as database migrations or batch jobs etc.
Job Patterns
One Shot
Cron Jobs
Lets create a Job which runs the alpine pod and we make it sleep for 60seconds so that the Job is completed. Refer Here for api reference
Lets create a Job Spec Refer Here
In Some Case we would like to run the job on certain time interval. Lets create a cron job Refer Here
Next Steps:
Configuration objects in k8s
Health Checks
Storage
Services, Ingress
AKS, EKS