Statefulsets | Deploying MongoDB cluster to Kubernetes

In this video, we'll learn:
1. Differences between Stateless and Stateful applications
2. What problems a Statefulset solves
3. Where to use Headless Services
4. Differences between Deployment and Statefulset
5. How to deploy a Stateful application with multiple replicas using Statefulsets with complete hands-on
Manifests: github.com/pelthepu/Kubernete...
Please give a Like and Subscribe - bit.ly/pavanelthepu
Timestamps:
0:00 - Intro
00:42 - Differences between Stateless and Stateful applications
2:17 - What problems a Statefulset solves
6:55 - Headless Services
8:14 - Differences between Deployment and Statefulset
9:15 - How to deploy a Stateful application with multiple replicas using Statefulsets
My other courses:
Docker Complete Course: • Docker Tutorial | Ful...
Thank you very much!
#kubernetes #statefulsets #fullstackdevelopment #devops

[@naveenchebolu6757]

This video clears all my doubts about statefulsets .Why this video not went viral.

[@kaykay02120]

no one can give better explanation than this. kudos to you pavan

[@dipi411]

Nice !Duration is short but every aspect of stateful set has been covered.

[@saikrishnareddybandi8285]

Ultimate level of teaching 🙏🙏🙏

[@vishalmishra176]

You kept it simple. Very helpful. Thank you.

[@PavanElthepu]

Thank you Vishal. Please share it with your friends and colleagues

[@ye__in]

Amazing amazing amazing!! Most helpful K8S video so far! Thank you so much

[@PavanElthepu]

Thank you so much. Please subscribe and share with your friends and colleagues

[@krushnabhanage5780]

You made it easy to understand, was really helpful. Keep up!!!!

[@PavanElthepu]

Glad that it helped you Krushna. Please share with your friends and colleagues

[@janvidalal476]

Your videos are GOLD!! 🎉

[@PavanElthepu]

Thank you so much🙂. Please share with your friends and colleagues

[@umeshsaini3109]

Again appreciated bro!! You have explained everything in detail. I wish I could have come on this channel earlier.

[@PavanElthepu]

Please connect with me on LinkedIn

[@neeharikagv2812]

This is so helpful. Concept and practicals in single video from end to end is amazing. Thank you so so much

[@PavanElthepu]

Love to hear that😊

[@chfr]

Good video, it explains the intricacies of stateful sets and headless services very well.

[@PavanElthepu]

Thank you so much. Please share with your friends and colleagues

[@kreebo_]

This content is amazing! You're so good at explaining and demo'ing. This helped me understand so much I did not fully grasp before. We need more in-depth content like this

[@PavanElthepu]

Thank you so much Cheslyn. Please subscribe and share with your friends and colleagues

[@liontechnologiessolutions8755]

​@@PavanElthepuI could get you a tutoring job. For about 6 hours a week. Please get in touch

[@vitusyu9583]

Your presentation is clear and yet comprehensive. Thanks! I just subscribed to your channel to watch more on K8.

[@PavanElthepu]

Thank you so much. Please share with your friends and colleagues🙏

[@TC-kt7pp]

Thank you this video helped me a lot, in fact you're all videos are great to understand easily.

[@PavanElthepu]

Thank you so much. Please subscribe and share with your friends and colleagues

[@aayush5474]

Your channel has best kubernetes tutorials. Thanks a lot for this

[@PavanElthepu]

Thank you so much Ayush. Please subscribe and share with your friends and colleagues

[@jalandharbehera2456]

Really sir....no words for you 🙏🙏 I already have share your most the videos because all should know you and your channel and that helps them most 🙏🙏🙏

[@PavanElthepu]

Thank you so much Jalandhar for your love🙏

[@HarshaVardhan-mr2bw]

was searching for this kind of video, thanks man, crystal clear from point to point, amazing, keep posting this content.

[@PavanElthepu]

Thank you so much HarshaVardhan. Please subscribe and share with your friends and colleagues

[@HarshaVardhan-mr2bw]

@@PavanElthepu Hey small doubt hope you could reply to this, how do we connect to the mongo compass from this replicaset, i tried the same method as the deployment, but it didnt work, hoping you could clarify this? Thanks

[@cloudpillsdaily]

more than gold thank you so much

[@sagarasgr]

Great tutorial 💯

[@ruptamsadhukhan7834]

Hey Pavan, Nice Explanation!!! I need to implement this using postgres.

[@PavanElthepu]

Yes, you can use same concept with PostgreSQL

[@jyothsnabethavalli9599]

Great tutorial

[@dummymail6029]

great video thanks pavan :)

[@PavanElthepu]

Looks like you are watching all my videos today🙂. I have received your comments on many videos

[@dummymail6029]

@@PavanElthepu yes i'm justing completing the playlist, since tomorrow there is an interview just referring all your video thank you so much for your clear explanation of concepts

[@taiz2908]

Nice explanation 👌🏻 Waiting for you to upload more videos

[@PavanElthepu]

Thanks you Taizun. Please share it with your colleagues and friends

[@taiz2908]

@@PavanElthepu sure..

[@eugenmalatov5470]

Really amazing, thanks a lot!

[@PavanElthepu]

Thank you so much, please subscribe and share with your friends and colleagues

[@pavankongara792]

amazing!

[@raghuvardhansaripalli9636]

Superb k8s series Pavan. Simple, crisp and clear with the content. I am following your series with handson. and all are working as you explained in videos. I shared your videos with my friends. I wish you to make more such videos and become popular in youtube with good growth. May i know your plan for the next series.? God bless you !!!

[@PavanElthepu]

Thanks for the love Raghu Vardhan. These words really motivates me to create so much of content. Yeah, plan Git, GitOps, ArgoCD, Terraform, General Software Development/Design concepts, Kafka, Redis, SpringBoot, and many more. This would be a FullStack channel, not just DevOps!

[@raghuvardhansaripalli9636]

@@PavanElthepu Superb Pavan. thanks for the headsup. i have subscribed your channel. by the way when i execute the comman "k exec -it mongo-0 -- mongo ". I am getting below error. OCI runtime exec failed: exec failed: unable to start container process: exec: "mongo": executable file not found in $PATH: unknown How to resolve this error. Can you please tell me Pavan. GOD BLESS YOU !!!

[@Mohammed-co3ux]

Hey buddy I have been into devops for quite some time now. This video is a gateway for many who make it hard to understand statefulset.. Way to go..

[@t.bikash62]

9 mins and straight searched the subscribe button!

[@PavanElthepu]

Means a lot. Please share with all your friends and colleagues

[@yashkinra7033]

loved it

[@navyabhanuchaganti6718]

Nice explanation wid figure 👍

[@PavanElthepu]

Thank you Navya. Please subscribe and share with your friends and colleagues

[@maheshkumarnaik754]

Nice sir

[@PavanElthepu]

Thank you Mahesh. Please subscribe and share with your friends and colleagues

[@abhinavkumar2099]

superb

[@PavanElthepu]

Thank you Abhinav. Please share with your friends and colleagues

[@walkerstark9584]

😭😭😭😭😭😭😭😭😭 You're the Best bro

[@PavanElthepu]

Ha ha🙂. Thank you so much. Please subscribe and share with your friends and colleagues

[@walkerstark9584]

@@PavanElthepu Done

[@marcikaist]

The explanation was very clear but I have a little problem, can you help me please? The first pod is created successfully, but at athe second pod I get the following message: Warning FailedScheduling 3m35s default-scheduler 0/1 nodes are available: pod has unbound immediate PersistentVolumeClaims. preemption: 0/1 nodes are available: 1 No preemption victims found for incoming pod.. Normal NotTriggerScaleUp 2m46s cluster-autoscaler pod didn't trigger scale-up:

[@sivakrishna-hk2un]

requesting you to Please make videos on kubernetes troubleshooting means errors and their solutions

[@PavanElthepu]

Sire Siva Krishna

[@user-zo3rj5xk8z]

Thanks a mil Pavan. A quick question. How to automate the manual efforts that are involved, like adding the replicas details to the primary pod always when the pod re-schedules or enabling the secondary pod to allow read operations when ever the pods are scaled ?

[@mrnikhil4898]

Hi Sir, Can the replication algorithm mentioned in the video be applied for mysql pods?

[@thangapandianm7862]

Thanks Pavan. it's really helpful. if I need to restart the mongoDB password then what should I do.

[@user-zo3rj5xk8z]

Thanks a mil Pavan. Just a quick question. do we have to always manually configure the secondary nodes to accept read requests when we scale up the pods ? or adding replica details manually to the primary pod if the pod rescheduled? what is the other way to get these manual process automated ?

[@gokhunyayla]

very good video, most helpful one. Now can you please tell me how can I connect via mongodb compass to the mongodb database that has this statefulset setup in GKE

[@manasas9671]

Thank you for the video, How can we configure master and slave in Mysql Database

[@andrevieira997]

Hello Pavan, Many thanks for sharing your knowledge. :) I just have a question, how can I connect to my mongo db cluster outside of the Kubernetes? Using a Mongo GUI like Compass. Can you help? Thank you.

[@rajangarg]

Thanks for the simplified explanation. I want to know is there any other condition apart from authentication which can make an application stateful?

[@PavanElthepu]

Doesn't matter, anything that you store for future usage makes an application Stateful. Examples: Redis, all DBs, all message brokers, etc..

[@SusmithaNikhil]

how do we configure the mongocompass to access the replicaset from internet

[@rajeshdheenan9913]

Hi Pavan, In non-Statefulsets Mongo pod with 4 replication factor. While user fetching the query in mongo db, how the services select which pod to select the data to the user. How it select which pod to select? Could you please explain it briefly. Thank You.

[@rahulpardeshi56]

How to take backup of DB deployed using Statefulsets in K8s CLuster??

[@jyothsnabethavalli9599]

Any video on mysql data replication please help and share any link please

[@developershourov4390]

how to expose this for mongodb compass?

[@parimalaprao]

Can you please make a tutorial on k8s certificates?? Why, how and when of those certificates?

[@swapnilgawade9048]

Its very helpful, thank you!! Can you please share the link of manifest files?

[@PavanElthepu]

Updated the description with manifest link Swapnil. Glad that it helped you, kindly share the video with your colleagues and friends.

[@thiagoacsoares]

Good evening, access to mongodb is occurring without a password. mongodb is not asking for username and password.

[@najibiziki4070]

hello, first thank you very much for this simple tutorial is clear. I have a question, and I hope you can help me with this problem. when i deploy mongodb with statefulsets , and i have deploy my server side , express js with deploy . in this case i have a primitive and secondary db. how i can conect mongodb your express so i can write in primitive and read from secondary db . in this pon where i am blocked, can you help me please

[@PavanElthepu]

Hi Najib, you can give read preference in connection string or in your code while doing database operations.

[@bharath4195]

what do you suggest deployment or statefulset ?

[@PavanElthepu]

I depends on your application. If you’re storing any state, the go for statefulset. If there is no state needed, go with deployment

[@himaniupadhyay4u]

Suppose we are creating a DB using StatefulSet object and we have masterNode-0 and slaveNode-1/2. If masterNode-0 goes down, will any slaveNode become master node or the whole service will stop responding to incoming request until masterNode comes-up?

[@harshupadhyay2032]

Have you got the answer, because I too am searching for the same

[@denkoech8712]

how do you replication automatically if you have enabled HPA?

[@PavanElthepu]

There are multiple ways of doing this like using Operator, adding a sidecar container, etc..

[@ShourovRoy-pk5zm]

Not working. And how to access from external?

[@jitendernegi9074]

1 Question : You said replication of data is not enabled by default . so if I scale the statefulset to one more pod , do I need to run the rs.initiate{} command again in the master pods with the dns of the new pod ??

[@PavanElthepu]

Yes. There are multiple ways of doing this like using Operator, adding a sidecar container, etc..

[@jitendernegi9074]

@@PavanElthepu thanks for the prompt response . The video is really very informative

[@PavanElthepu]

Thank you Jitender. Please subscribe and share with your friends and colleagues

[@eugenmalatov5470]

@@PavanElthepu Follow-up question. The fact that you need to exec specifically into a pod to run some commands and initiate the "replication/synchronization". Does that mean that things need to be redone (exec + scripts) every time when some pods go down and reboots (because the IP will change and all that)? This would defeat this auto-repair property of Kubernetes.

[@PavanElthepu]

It doesn't, as that script execution is automated on every pod creation

[@roopesh668]

So, If 1 replica of mongodb is enough then the kind of Deployment is enough right?

[@PavanElthepu]

Yes, you can use a Deployment instead of a StatefulSet to deploy a single replica of MongoDB. However, there are some important differences between the two that you should consider before making a decision. A StatefulSet is typically used when you need to manage stateful applications that require stable, unique network identities and persistent storage. MongoDB is a stateful application, and using a StatefulSet ensures that each replica has a unique identity and that data is stored persistently. On the other hand, a Deployment is typically used for stateless applications that can be scaled horizontally. MongoDB can also be deployed in a stateless manner, with a single replica running in a container, and a Deployment can be used for this purpose. Using a StatefulSet for a single MongoDB replica provides some benefits, such as: Unique network identity: Each replica will have a unique hostname that can be used to communicate with it, even if the replica is restarted. Persistent storage: Each replica will have its own persistent volume, which ensures that data is retained even if the replica is restarted or moved to a different node. Ordered startup and shutdown: StatefulSets ensure that replicas are started and stopped in a specific order, which can be important for stateful applications. However, if you only need a single MongoDB replica and do not require these benefits, a Deployment can be used instead. It is simpler to set up and manage, and can still be scaled horizontally if needed in the future.

[@HarshaVardhan-mr2bw]

Hi, can anyone guide me to connect this statefulset replicaset to the mongo compass. Thank you

[@PavanElthepu]

Hi Harsha, you mean you want to connect to statefulset from Mongo compass?

[@HarshaVardhan-mr2bw]

@@PavanElthepu yes

[@PavanElthepu]

Watch my jobs and cronjobs video. There I gave the connection uri. You may use it from Mongo Compass

[@chennareddy2770]

Hi @PavanElthepu, Your videos are amazing they are very simple to understand. I have a question with the example you have shared in the statefulset.yaml file in the GitHub repo. If I have to mount mongodb.conf file under same /data/db under mongo-volume volumemount how do I do it.

[@subbareddyjangalapalli6310]

Hello Pavan, getting error after statefulsets deployed with mango-0 "exec failed: container_linux.go:380: starting container process caused: exec: \"mongo\": executable file not found in $PATH"" - can you help to throw some light.

[@PavanElthepu]

Did you use same manifest?

[@subbareddyjangalapalli6310]

@@PavanElthepu Thank you for quick reply Pavan. I'm good with image:4.0.8 no issues as you mentioned in your yaml file, where as if I use latest image, can you do post for latest image

[@PavanElthepu]

@@subbareddyjangalapalli6310 sure, I'll try

[@sriramakrishnas9248]

Hi This video is really awesome which made our lives easy...when try to deploy the statefulset with above scripts, we getting below error here.. We have used the same files in the repo for secrets,sc,pv,pvc and config.. default-scheduler 0/1 nodes are available: pod has unbound immediate PersistentVolumeClaims. preemption: 0/1 nodes are available: 1 No preemption victims found for incoming pod.. Normal Scheduled 98s default-scheduler Successfully assigned default/mongo-0 to minikube Warning FailedMount 66s (x7 over 98s) kubelet MountVolume.SetUp failed for volume "mongodb-config" : configmap "mongodb-config" not found Normal Pulling 33s kubelet Pulling image "mongo:4.0.8".. I any information will be helpful..

[@PavanElthepu]

Thank you Sri Rama Krishna. It’s saying that configmap not found

[@sriramakrishnas9248]

@@PavanElthepu Thanks Pavan..

[@sriramakrishnas9248]

Hi Pavan.. Thanks for your time. can we create a mongodb instance with single replicaset .will that serves our purpose for read & write operations...How we need to do the replica setup for single pod..?

[@siddharthgaur6854]

@pavan: How to self host typesense on K8 cluster using deployment.yaml

[@PavanElthepu]

Typesense should be deployed using Statefulset as it’s a stateful application.

[@nihalahmed6302]

Great explanation pavan.. i tried the demo but i am unable to create replication. I am getting below error: rs.initiate( { _id: "rs0", members: [ { _id: 0, host: "mongo-0.mongo.default.svc.cluster.local:27017" }, { _id: 1, host: "mongo-1.mongo.default.svc.cluster.local:27017" }, { _id: 2, host: "mongo-2.mongo.default.svc.cluster.local:27017" } ] } ) { "operationTime" : Timestamp(0, 0), "ok" : 0, "errmsg" : "No host described in new configuration 1 for replica set rs0 maps to this node", "code" : 93, "codeName" : "InvalidReplicaSetConfig", "$clusterTime" : { "clusterTime" : Timestamp(0, 0), "signature" : { "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="), "keyId" : NumberLong(0) } } } could you please check and let me know what might be the issue ? Thanks !!!

[@vuat1494]

now 2023: i meet issue about init primary node and secondary node "errmsg" : "replSetInitiate quorum check failed because not all proposed set members responded affirmatively: mongo-1.mongo.mongodb.svc.cluster.local:27017 failed with Couldn't get a connection within the time limit", "code" : 74, "codeName" : "NodeNotFound", i need help