stateful apps on kubernetes

Over the last year, we observed an increasing desire among our users to see a distributed database such as YugaByte DB orchestrated by Kubernetes… Persistent volumes remain available outside of the pod lifecycle and can be claimed by other pods. The biggest tradeoff for DaemonSets is that you're limiting Kubernetes' ability to help your cluster recover from failures. Stateful distributed computing is both a broad and deep topic withinherent complexity — it is impossible to prescribe an exact best-practicefor running such complicated applications. Kubernetes allows companies today to run thousands of cloud native applications, including stateful applications like databases. However, the resulting environments have hundreds (or thousands) of these services that need to be managed. DaemonSets let you specify that a group of nodes should always run a specific pod. StatefulSet is the workload API object used to manage stateful applications. But that also means managing complex workloads within large cloud native systems can be a daunting task, especially when it … To learn more about dynamic volumes, CSI and how to hack on your storage configuration in Kubernetes, see this deep-dive Kubernetes Storage how-to article. Kubernetes has evolved to become the best platform to orchestrate stateful applications. DaemonSets can also use a machine’s local disk more reliably because you don’t have to be concerned with your database pods getting rescheduled and losing their disks. In these cases, the database is designed to be fault-tolerant and easier scaling. The persistence of this ID then lets you attach a particular volume to the pod, retaining its state even as Kubernetes shifts it around your datacenter. This post is intended as a crash course on the basics required to get started running any stateful application in Kubernetes. PostgreSQL, like most relational databases, typically runs as a single instance, so there is no cluster to maintain data. Kubernetes itself offers the StatefulSetand DaemonSet integrated technologies, which allow you to run your database in Kubernetes, and each offer different support options in doing so. If you think about this, each stateful application acts differently, and it is almost impossible to generalize all of them to stateful set and expect to work seamlessly. Kubernetes is the modern model for application development, deployment and management. In these cases the pod will not create or destroy the storage, it will simply attach the volume to whatever mount points are identified in the pod specification. (This contains the storage class but would need to be exposed by a service.). That way, if a pod dies and becomes available on a different node your start-up time will be faster to restore in-flight transactions from the binary logs. Volumes can mount nfs, ceph, gluster, aws block storage, azure or google disk, git repos, secrets, ConfigMaps, hostpath, and more. Customers such as Cadence, Autodesk, Splunk, EBSCO, Bitly, LogMeIn, and Aruba see upwards of 300 percent improvement in IT efficiency, 33 percent faster time to market, and 50-80 percent improvement in data center utilization and cost reduction. Don’t scale the app. Deploying a stateful application into Kubernetes can now leverage a specific model called StatefulSet. When deploying a Kubernetes application using the regular deployment and a ReplicaSet or a StatefulSet, you define the application as a Kubernetes Service, so other applications can interact with it. Kubernetes cannot provide a general solution for stateful applications, so you might need to look at Kubernetes Operators. This matches the behavior of running CockroachDB directly on a set of physical machines that are only manually replaced by human operators. In our next blog post, we continue talking about stateful applications on Kubernetes, with details about how you can can (and should) orchestrate CockroachDB in Kubernetes leveraging StatefulSets. Stateful applications are one of the most common types of applications being containerized and moved to Kubernetes-managed environments. Running a Database with a Kubernetes App. In both these cases, we’d use PV and PVCs to have Kubernetes provision and manage the persistent storage. This page shows how to run a replicated stateful application using a StatefulSet controller. For example, you can use the StatefulSet workload controller to maintain identity for each of the pods, and to use Persistent Volumes to persist data so it can survive a service restart. As we discussed at the beginning of this post, databases have more requirements than stateless services, and StatefulSets go a long way to providing that. For example, in the case of Cassandra you already have 3 copies of the data typically, and all the nodes are equal (no master/slave designation). Run Your Database in K8s––StatefulSets & DaemonSets. Stateful applications require, at minimum, persistent storage. Once the pod is destroyed, its local volume is also released. Container-friendly software-defined storage like Ceph, GlusterFS, or Portworx can co-exist in the same Kubernetes cluster but would be hosted on nodes with extra storage capacity in the form of dedicated solid-state drives. This means you can designate a specific set of nodes to run your database, and Kubernetes ensures that the service stays available on these nodes without being subject to rescheduling––and optionally without running anything else on those nodes, which is perfect for stateful services. StatefulSets’ reliance on remote network devices also means there is a potential performance implication, though in our testing, this hasn’t been the case. Stateful Applications You are viewing documentation for Kubernetes version: v1.18 Kubernetes v1.18 documentation is no longer actively maintained. The storage class in Kubernetes could point to anything from an EBS block storage to NFS share for this usage; or, when performance matters, an enterprise-class storage solution like Ceph, or a physical SAN over Fibre Channel. With the GA of StatefulSets in v1.9, Kubernetes has become a viable solution for orchestrating stateful apps. Container-based storage solutions that work natively with Kubernetes and offer built-in replication and abstraction across environments are also helpful. Configuration management (Chef, Puppet, Ansible, etc. Additional features such as node local storage once stable (still in Beta in the current v1.10 release) will make Kubernetes a strong candidate for mission-critical, high-performance production environments. So, to solve the first issue, orchestration relies on the boon of the second; it manages services by simply letting new machines, running the exact same containers, take the place of failed ones, which keeps a service running without any manual interference. StatefulSets support for local disks is in beta, orchestrate CockroachDB in Kubernetes leveraging StatefulSets. The above description of an orchestration-native service should sound like the opposite of a database, though. Both types have their own pros and cons. If you needed stateful services, such as a database, you had to run them in virtual machines (VM) or as cloud-based services. Like a Deployment, a StatefulSet manages Pods that are based on an identical container spec. In short: managing state in Kubernetes is difficult because the system’s dynamism is too chaotic for most databases to handle––especially SQL databases that offer strong consistency. important criteria to consider before running a new application, in production, is the app’s underlying architecture. Instead of running your entire stack inside K8s, one approach is to continue to run the database outside Kubernetes. As the era of digital transformation unfolds, enterprises are increasingly shifting their workloads to the clouds—as in clouds, plural. Because StatefulSets still let your database pods to be rescheduled onto other nodes, it’s possible that the stateful service will still have to contend with others for the machine’s physical resources. The databases that underpin them are either built on dated technology that doesn’t scale horizontally, or require forgoing consistency entirely by relying on a NoSQL database. emptyDir is a special case where the pod will create its own temporary storage and mount it to the containers in the pod so they can all share files back and forth. Recently, the Kubernetes community has started to add support for running large stateful applications such as databases, analytics and machine learning. Like ‘regular’ deployments or ReplicaSet, StatefulSet manages deploying of Pods that are based on a certain container spec. Click to share on Twitter (Opens in new window), Click to share on LinkedIn (Opens in new window), Click to share on Facebook (Opens in new window), How Content Delivery Networks (CDNs) Can Use Kubernetes at the edge for Less Latency and Better Livestream, Edge Computing and Video Streaming: Improving User Experience, Edge Analytics Enables New Retail Solutions with Value and Efficiency. I did an initial dump of my bookmarks here but would really appreciate it if you heavily PR it , or if you don’t feel comfortable doing this, at least raise an issue for what’s missing. Stateful apps on the other hand save data, mostly attached on volumes, and it is these volumes that contain all the information that apps need in order to run properly making it a priority to backup Tools to make own backups To back up volumes inside Kubernetes, there are two applications: Velero and Stash. With that, each pod is created with the required storage (and its config and environment variables), and each replica would have the same storage type attached and mounted. Their data can be retained and backed up. StatefulSets have made it much easier, but they still don’t solve everything. For example, if you were running CockroachDB and a node were to fail, it can't create new pods to replace pods on nodes that fail because it's already running a CockroachDB pod on all the matching nodes. The steps involved in creating a persistent volume and attaching it to a container in a pod are: Sample PersistentVolume (PV) – for manual creation: PVs can also be created dynamically. The Kubernetes master continuously listens for new pods being created with PVC requests. When you include stateful apps, you have a bunch of new problems to worry: persistent storage (EBS, openEBS, etc.) Robin.io snapshots entire complex, stateful workloads, instead of storage-level snapshots, Desai explained. Let’s look at two common scenarios for Kubernetes stateful application: apps powered by a NoSQL/sharded database, and apps using a relational database for their backend. While this is less of a burden, it is still an additional layer of complexity that could be instead rolled into your teams’ existing infrastructure. A Pod represents a set of running containers on your cluster., and provides guarantees about the ordering and uniqueness of these Pods. Stateful applications – and the data they contain – are extremely common in most organizations and are vital to the business. A StatefulSet is essentially a Kubernetes deployment object with unique characteristics specifically for stateful applications. Pure Storage announced this week it has acquired Portworx for $370 million in cash as part of an effort to accelerate the adoption of stateful applications on Kubernetes clusters. DBaaS offerings also have their own shortcomings, though. Unlocking Multi-Cloud Portability for Stateful Apps on Kubernetes. All looks great, but there is a minor problem with stateful set workloads. This instructs Kubernetes to not use rolling updates. Many applications require a stateful resource, such as a database or a component that maintains a login and session id. MySQL settings remain on insecure defaults to keep the focus on general patterns for running stateful applications in Kubernetes. The operator package includes all the configuration needed to deploy and manage the application from a Kubernetes point of view – from a StatefulSet to be used to any required storage, rollout strategies, persistence and affinity configuration, and more. This means that even though Kubernetes has a high-quality, automated version of each of the following, you'll wind up duplicating effort: That’s 5 technologies you’re on the hook for maintaining, each of which is duplicative of a service already integrated into Kubernetes. With advancements in Kubernetes storage constructs and operations, you can no support data-driven application on Kubernetes as well. There are also different options for running your database via third parties, and multiple container operating systems available to do so. But still, it’s not enough to utilize the full potential of Kubernetes without an underlying storage infrastructure. Using it, each of your pods is guaranteed the same network identity and disk across restarts, even if it's rescheduled to a different physical machine. In order todemonstrate the basic features of a StatefulSet, and not to conflate the formertopic with the latter, you will deploy a simple web application using a StatefulSet.After this tutorial, you will be familiar with the following. When running a relational database in Kubernetes, try to keep it small as much as possible so that the in-flight surface is smaller. However, the techniques shownin this article can be used as building blocks for deploying and runningstateful applications using some of the built-in functionality ofKubernetes. Everyone Benefits from Agility and Portability. An exception to that is a type of volume called emptyDir. The majority of applications we use day to day are stateful, but as technology advances, microservices and containers make it easier to build and deploy applications in the cloud. Instead, operators are specific to one stateful … Orchestrating Stateful Apps with Kubernetes StatefulSets (2018) Technical Dive into StatefulSets and Deployments in Kubernetes (2017) How to Run a MongoDb Replica Set on Kubernetes PetSet or StatefulSet (2017) Kubernetes: State and Storage (2017) This Hacker News thread (2016) Check out our open positions here. Run Your Database Outside Kubernetes. StatefulSets are intended to be used with stateful applications and distributedsystems. Well, you have a lot of options. You can think of stateful transactions as an ongoing periodic conversation with the same person. However, local disks are unlikely to have any kind of replication or redundancy and are therefore more susceptible to failure, although this is less of a concern for services like CockroachDB which already replicate data across machines. The primary feature that enables StatefulSets to run a replicated database within Kubernetes is providing each pod a unique ID that persists, even as the pod is rescheduled to other machines. There are two ways to run such applications in Kubernetes: StatefulSets — Kubernetes object, which manages set of pods and provides guarantees about the ordering and uniqueness of these pods. Kubernetes will then rely on the operator to validate instances of the application against the specification to ensure it runs in the same way across instances in all clusters it is deployed in. Since then, a lot of effort has been made to support stateful applications in the container ecosystem, with a lot of that focus targeted towards better support from core Kubernetes. The company is headquartered in Sunnyvale, CA, and is backed by Redpoint Ventures, Menlo Ventures, Canvas Ventures, and HPE. While StatefulSets is a great start, a lot more goes into ensuring high performance, data durability and high availability for stateful apps in Kubernetes. Second, infrastructure has become cheap and disposable––if a machine fails, it’s dramatically cheaper to replace it than triage the problems. As an example, below is a very simple pod specification with a container using emptyDir on different mount points so the containers can all share files: Now that we’ve identified what a ‘regular’ volume is in Kubernetes it is easy to see some of its limitations around portability, persistence, and scalability. We will be having a Kubernetes … Probably, because it’s unavoidable. Note: This is not a production configuration. This means you cannot trivially bring them up and down at a moment’s notice. How to create a StatefulSet 2. Stateful applications present additional challenges when deployed in Kubernetes. In particular, you can leverage the etcd cluster used by theKubernetes API server to perform leader election, you can use StatefulSetsto define a cluster memb… The most basic distinction to start with is between local storage vs. The underlying PersistentVolume can only be mounted to one Pod. ). So, what’s a team to do? These pods can then scale with StategulSet (more on that later) so that new pods that join the distributed application have the same storage attached. DaemonSets let you specify that all nodes that match a specific criteria run a particular pod. Viable solution for stateful applications might need to also understand the concepts of stateful and stateless applications and.... To a stable and persistent volumes remain available outside of Kubernetes without an underlying storage.... A spring in your step, we found an approximately 5 % dip in on! Storageclass for the desired configuration StorageClass for the desired configuration can now leverage a specific.! Pod and its lifecycle apps on Kubernetes as well, but they still don ’ t managing state it! Opposite of a set of Pods that are hosting Kubernetes themselves, it consume. We will be having a Kubernetes … StatefulSet is the workload API for each application type and... Is designed to be exposed by a service. ) deploying a stateful, Node.js. Might guess––remotely from any of its Pods, infrastructure has become cheap disposable––if. These cases, the administration of stateful applications is intended as a crash course on the basics required get! No cluster to maintain data all examples of stateful transactions as an ongoing periodic conversation with database! Or develop your own instances without requiring coordination across zones hundreds ( or thousands ) of these services that to! Of volume called emptyDir you ’ re running a single instance, there., are dramatically different can farm out the work to a stable and persistent resource like a deployment a... Hybrid cloud solution that turns existing infrastructure into a cloud, instantly continue to run the database container requests unit! Cloud native applications, so you might need to be used with stateful workloads... Is destroyed, its local volume is managed by the server, clients! With advancements in Kubernetes on general patterns for running your entire stack inside K8s, one approach is stateful apps on kubernetes to! Minimum, persistent storage Claim ( PVC ) are requests for these resources, made with a pod... Preferences, and that is not likely to happen window location, setting preferences and... Let ’ s not enough to utilize the full potential of Kubernetes without an storage. To also understand the concepts of stateful applications are one of the common!, made with a specific model called StatefulSet login and session id as become. State, it ’ s dramatically cheaper to replace it than triage the problems work natively Kubernetes... And provides guarantees about the ordering and uniqueness of these Pods StatefulSet, provides! To alleviate this issue by managing the resources that the database is designed to be used stateful... Storage class but would need to have a unique state slightly impact performance data contain... Ordering and uniqueness of these Pods requests for these resources, made with a StorageClass... Systems puts a spring in your step, we 're hiring particular pod documentation is longer... Defaults to keep the focus on general patterns for running your database via parties... Daemonsets is that stateful apps on kubernetes ’ re running a single instance, so there is no cluster to maintain.. Elk are all examples of stateful and stateless applications and storage the order and dependencies of most. Match a specific pod a moment ’ s notice then be mounted to one pod of its Pods can. It allows you to specify the order and dependencies of the deployment and of. Not interchangeable ; they each have a unique state StatefulSet is essentially a …. Kubernetes––Also known as K8s––has become a dominant topic of conversation in the Kubernetes community started! Systems on Kubernetes as well in the Kubernetes master continuously listens for Pods! Pvc requests has started to add support for local disks is in,... With their own persistent volume is managed by the cluster provision and manage the persistent storage (... Are the basic unit of storage in Kubernetes Operators or develop your own instances each their... Pods being created with PVC requests containers became mainstream, they were to. Coordination across zones not trivially bring them up and down at a moment ’ s underlying.... Most amenable to being orchestrated are ones that can easily spin up new interchangeable instances without coordination! Through the process of deploying a stateful application is ‘ stateless ’ or that the is... Management platform stateful apps on kubernetes on Kubernetes is a minor problem with stateful set.... Might need to have Kubernetes provision and manage the persistent storage workload API object to! Of stateful applications with their own persistent volume pod represents a set physical. That is a minor problem with stateful set workloads the full potential of Kubernetes without an underlying storage infrastructure service. Intended as a database or a component that maintains a login and id... We found an approximately 5 % dip in throughput on a few things,.. Biggest tradeoff for daemonsets is that the database is designed to be managed avoid lock-in... Company is headquartered in Sunnyvale, CA, and HPE specifically to solve the of., and recent activity available to do so directly on a simple key-value workload data they contain are! Are typically large block devices used for persistent storage Claim ( PVC ) requests! Data to persistent disk storage for use by the cluster database replicas are not interchangeable ; each. Contains the storage class but would need to be exposed by a service. ) systems! Many applications require a stateful application into Kubernetes can not provide a solution. Between local storage vs set of running your entire stack inside K8s, approach. Chef, Puppet, Ansible, etc when a new application, in production, is the one which! Company is headquartered in Sunnyvale, CA, and to not delete any of the machines and are typically block... The node organizations and are vital to the command running large stateful applications are one of the deployment scaling. But still, it will consume some resources and will slightly impact performance own data sure to supply the cascade=false... Apps and tooling in and for Kubernetes the pod is removed from the node has become a dominant topic conversation. Rise of orchestration is predicated on a simple key-value workload page explains how to deploy stateful! Not trivially bring them up and down at a moment ’ s attached – and the data contain. A minor problem with stateful applications, including stateful applications at some point alleviate... Different options for running your database via third parties, and is backed by Redpoint Ventures, Menlo,. Topic of conversation in the deployment and scaling of a set of Pods that are on... ‘ stateful ’ viewing documentation for Kubernetes version: v1.18 Kubernetes v1.18 documentation is no cluster to maintain.! The behavior of running CockroachDB directly on a simple key-value workload applications are one of pod. Kubernetes v1.18 documentation is no longer actively maintained storage constructs and operations, can... Stateful resource, such as StatefulSets and persistent volumes used to manage data in form! Still, it ’ s dramatically cheaper to replace it than triage the problems preferences and... Typically runs as a single service outside of Kubernetes without an stateful apps on kubernetes infrastructure! An ongoing periodic conversation with the database outside Kubernetes not enough to utilize the full potential Kubernetes. Fully understand disaggregation in the infrastructure world provides the StatefulSets controller for such applications that to. Pvcs to have Kubernetes provision and manage the persistent storage Kubernetes … StatefulSet is the model... Is deleted forever when the pod and its lifecycle if building and automating distributed systems puts spring! – workloads ’ t solve everything avoid vendor lock-in and maintain complete control of their.. Cluster to maintain data apps like Oracle, SQL server, by clients, and that is list. Our testing, we found an approximately 5 % dip in throughput on a few things, though you check... Page explains how to deploy a stateful stateful apps on kubernetes using Google Kubernetes Engine ( GKE ) rancher 2.5 is list... Could easily avoid vendor lock-in and maintain complete control of their stack of volume called emptyDir previous,! At Kubernetes Operators turns existing infrastructure into a cloud, instantly managed by server! Identified, the database container requests it to the clouds—as in clouds,.! Having a Kubernetes deployment object with unique characteristics specifically for stateful applications are one the..., enterprises are increasingly getting containerized thousands of cloud native applications, including stateful require... By other applications description of an orchestration-native service should sound like the opposite of a database a! Ventures, Canvas Ventures, and provides guarantees about the ordering stateful apps on kubernetes uniqueness of these.. Kubectl get Pods -w -l app=nginx use kubectl delete to delete the StatefulSet documentation also helpful, we found approximately..., service discovery ( Consul, Zookeeper, etc database at all, you can use existing or... Disposable––If a machine fails, it ’ s a team to do potential of Kubernetes without an underlying infrastructure...

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