How to delete a Pod in Kubernetes - Beginner tutorial

Delete a pod using kubectl delete pod

Sometimes we encounter some issues on running pod and then we decide to delete a Pod because we can't create a new pod with the same name. You can't have two pods with same name in a cluster. 

There are two ways to delete a pod: 

• Using delete command
• Using delete command with force keyword

The first way of deleting the pod is called a graceful delete. So before deleting any pod we first need to create a new pod.

Create a pod

To create a pod we need to run below command in our terminal.

kubectl run nginx --image=nginx --restart=Never

Above command will run nginx image with pod name nginx itself. 

Here --restart flag says kubernetes to create a single pod not to create a deployment.

Now check if the pod is running using below command

kubectl get pod

Output:

NAME    READY   STATUS              RESTARTS   AGE

nginx   0/1     ContainerCreating   0          8s

Just wait for few seconds and pod will be created.

kubectl get pod

NAME    READY   STATUS    RESTARTS   AGE

nginx   1/1     Running   0          2m6s

Since we have created our pod. Now lets try to delete it. To delete a pod you can use below command.

kubectl delete pods nginx

Here in the syntax you need to pass pod name that's it. In this case I passed nginx.

This may take some time depending upon pod usage. But if you want this to be deleted quickly then we can use force flag in the command.

A pod is not deleted automatically when a node is unreachable.The pods running on an unreachable Node enter the terminating or unknown state after timeout. Pods may also enter these states when user attempts graceful deletion of pod on unreachable node. The only ways in which a pod can be deleted/removed from apiserver are as follows:

• The node object is deleted.
• The kubelet on unresponsive node starts responding ,kills the pod and removes the pod from apiserver.
• Force deletion of pod by user.

The recommended best practice is to follow first two from above. If a node is confirmed to be dead then

delete the node object. Normally system deletes the pod once it's no longer running on a node or the node is deleted by administrator. 

Delete the pod forcefully using below command:

kubectl delete pod nginx --force 

Output:

pod "nginx" force deleted

If even after above command the pod is still stuck on unknown state. You can use the below command to remove the pod from the cluster.

kubectl patch pod nginx -p '{"metadata":{"finalizers":null}}'

That was it about deleting the pod using kubectl command. Be careful while deleting a pod especially using the force keyword.

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SQL query to find duplicate records

Introduction

These days data is growing massively and since the data is growing the amount of bad data is also growing. Today we'll talk about one form of bad data which we can call duplicate data. We use few database management systems to store and process the data ie sql server, postgresql, oracle etc. We store lot of data in these systems but sometimes we get lot duplicate data as well in our systems which can impact the true data and reporting on which lot of businesses and important decisions are dependent.

  So for us working on data, it's very important to identify the duplicates and remove them from the database which help businesses towards better reporting. 

Let's get into the practical to understand the duplicates. First we need to create a table with few columns.

In this tutorial I am using postgresql. 

CREATE TABLE duplicate_data_test(

id int,

name text

)

now let's insert some data with duplicates.

insert into duplicate_data_test values(1,'One');

insert into duplicate_data_test values(1,'One');

insert into duplicate_data_test values(2,'two');

insert into duplicate_data_test values(3,'three');

insert into duplicate_data_test values(4,'four');

insert into duplicate_data_test values(5,'three');

Query the data to see results:

select * from duplicate_data_test;

Let's find the duplicates for entire row.

select id,name,count(*) as count from duplicate_data_test

group by id,name having count(*) > 1;

or

Using CTE as well to get the duplicates.

with cte(id,name)

as

(select id,name,row_number() over (partition by id,name order by id) as rn

from duplicate_data_test)

select * from cte;

Above query will give you the count. You can remove the count in select list if you want and then you will get duplicate record without count number. 

Sometimes we want to find duplicates based on one column. Sometime we don't have entire row is duplicate rather just one column have some duplicate values. 

So we can definitely use partition by clause like below.

select * from (

select id,name,rank() over (partition by name order by id) as rnk

from duplicate_data_test

) as dt where dt.rnk > 1

Conclusion

That was it about duplicates. Always test above code in lower environment before implementing in Production.