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1. Introduction - Programming Kubernetes [Book]
LinOxide 2 6 Kubernetes - App Deployment Flow 64 7 Kubernetes – Auto scaling 66 8 Destroying Kubernetes Cluster and Pods 71 6. Deploying Kubernetes with Ansible 72 7. Provisioning Storage in Kubernetes 80 1 Kubernetes Persistent Volumes 81 2 Requesting storage 83 3 Using Claim as a Volume 84 4 Kubernetes and NFS 85 5 Kubernetes and iSCSI 87 8. Troubleshooting Kubernetes . · Programming Kubernetes: Developing Cloud-Native Applications If you’re looking to develop native applications in Kubernetes, this Programming Kubernetes is your guide. Developers and AppOps administrators will learn how to build Kubernetes-native applications that interact directly with the API server to query or update the state of resources. Read Online Programming Kubernetes and Download Programming Kubernetes book full in PDF formats.
Programming kubernetes download pdf
Programming Kubernetes can mean different things to different people. We will define what exactly we mean by programming Kubernetes, what Kubernetes-native apps are, and, by having a look at a concrete example, what their characteristics are. We will discuss the basics of controllers and operators, and how the event-driven Kubernetes control plane functions in principle, programming kubernetes download pdf.
When developing locally, you have a number of options available. Depending on your operating system and other preferences you might choose one or maybe even more of the following solutions for running Kubernetes locally: kindk3d programming kubernetes download pdf, or Docker Desktop. We also assume that you are a Go programmer—that is, you have experience or at least basic familiarity with the Go programming language.
Now is a good time, if any of those assumptions do not apply to you, to train up: for Go, we recommend The Go Programming Language by Alan A. Donovan and Brian W. For Kubernetes, check out one or more of the following books:. Kubernetes in Action by Marko Lukša Manning. Why do we focus on programming Kubernetes in Go?
Well, an analogy might be useful here: Unix was written in the C programming language, and if you wanted to write applications or tooling for Unix you would default to C. Also, in order to extend and customize Unix—even if you were to use a language other than C—you would need to at least be programming kubernetes download pdf to read C. Now, Kubernetes and many related cloud-native technologies, from container runtimes to monitoring such as Prometheus, are written in Go. We believe that the majority of native applications will be Go-based and hence we programming kubernetes download pdf on it in this book, programming kubernetes download pdf.
Should you prefer other languages, programming kubernetes download pdf, keep an eye on the kubernetes-client GitHub organization. It may, going forward, contain a client in your favorite programming language.
Besides, programming kubernetes download pdf, in Chapter 7we do not really focus too much on operational issues, but mainly look at the development and testing phase. So, in a nutshell, this book is about developing genuinely cloud-native applications. Figure might help you soak that in better. As you can see, there are different styles at your disposal:. Take a bespoke app, something you wrote from scratch, with or without having had Kubernetes as the runtime environment in mind, programming kubernetes download pdf, and run it on Programming kubernetes download pdf. The same modus operandi as in the case of a COTS applies.
The case we focus on in this book programming kubernetes download pdf a cloud-native or Kubernetes-native application that is fully aware it is running on Kubernetes and leverages Kubernetes APIs and resources to some extent. The price you pay developing against the Kubernetes API pays off: on the one hand you gain portability, as your app will now run in any environment from an on-premises deployment to any public cloud providerand on the other hand you benefit from the clean, declarative mechanism Kubernetes provides.
We call this cnat or cloud-native atprogramming kubernetes download pdf, and it works as follows. A custom resource called cnat. In addition, a kubectl plug-in for the CLI UX would be useful, allowing simple handling via commands like kubectl at " Jul 3" echo "Kubernetes native rocks! Throughout the book, we will use this example to discuss aspects of Kubernetes, programming kubernetes download pdf, its inner workings, and how to extend it.
For the more advanced examples in Chapters 8 and 9we will simulate a pizza restaurant with pizza and topping objects in the cluster, programming kubernetes download pdf. Kubernetes is a powerful and inherently extensible system. So-called cloud providerswhich were traditionally in-tree as part of the controller manager. As of 1. Cloud providers allow the use of cloud provider—specific tools like load balancers or Virtual Machines VMs, programming kubernetes download pdf.
Binary kubelet plug-ins for networkdevices such as GPUsstorageand container runtimes. Access extensions in the API server, such as the dynamic admission control with webhooks see Chapter 9.
Custom resources see Chapter 4 and custom controllers; see the following section. Custom API servers see Chapter 8. Scheduler extensions, such as using a webhook to implement your own scheduling decisions, programming kubernetes download pdf.
In the context of this book we focus on custom resources, controllers, webhooks, and custom API servers, along with the Kubernetes extension patterns. Per the Kubernetes glossarya controller implements a control loop, watching the shared state of the cluster through the API server and making changes in an attempt to move the current state toward the desired state.
Controllers can act on core resources such as deployments or services, which are typically part of the Kubernetes controller manager in the control plane, or can watch and manipulate user-defined custom resources.
Operators are controllers that encode some operational knowledge, such as application lifecycle management, along with the custom resources defined in Chapter 4. In general, the control loop looks as follows:. Read the state of resources, preferably event-driven using watches, as discussed in Chapter 3. Change the state of objects in the cluster or the cluster-external world.
For example, launch a pod, create a network endpoint, or query a cloud API. Update status of the resource in step 1 via the API server in etcd. No matter how complex or simple your controller is, these three steps—read resource state ˃ change the world ˃ update resource status—remain the same. The control loop is depicted in Figure which shows the typical moving parts, with the main loop of the controller in the middle.
This main loop is continuously running inside of the controller process. This process is usually running inside a pod in the cluster. From an architectural point of view, a controller typically uses the following data structures as discussed in detail in Chapter 3 :. Informers watch the desired state of resources in a scalable and sustainable fashion. Essentially, a work queue programming kubernetes download pdf a component that can be used by the event handler to programming kubernetes download pdf queuing of state changes and help to implement retries.
Resources can be requeued in case of errors when updating the world or writing the status steps 2 and 3 in the loopor just because we have to reconsider the resource after some time for other reasons.
The Kubernetes control plane heavily employs events and the principle of loosely coupled components. Other distributed systems use remote procedure calls RPCs to trigger behavior.
Kubernetes does not. Kubernetes controllers watch programming kubernetes download pdf to Kubernetes objects in the API server: adds, programming kubernetes download pdf, updates, and removes. When such an event happens, the controller executes its business logic. For example, in order to launch a pod via a programming kubernetes download pdf, a number of controllers and other control plane components work together:.
The deployment controller inside of kube-controller-manager notices through a deployment informer that the user creates a deployment. It creates a replica set in its business logic. The replica set controller again inside of kube-controller-manager notices through a replica set informer the new replica set and subsequently runs its business logic, which creates a pod object.
The scheduler inside the kube-scheduler binary —which is also a controller—notices the pod through a pod informer with an empty spec. Its business logic puts the pod in its scheduling queue. Meanwhile the kubelet —another controller—notices the new pod through its pod informer. It ignores the pod and goes back to sleep until the next event. The scheduler takes the pod out of the work queue and schedules it to a node that has enough free resources by updating the spec. The kubelet wakes up again due to the pod update event.
It again compares the spec. The names match, and so the kubelet starts the containers of the pod and reports back that the containers have been started by writing this information into the pod status, back to the API server.
Eventually the pod terminates. The replica set controller notices the terminated pod and decides that this programming kubernetes download pdf must be replaced. It deletes the terminated pod on the API server and creates a new one. As you can see, a number of independent control loops communicate purely through object changes on the API server and events these changes trigger through informers.
All of this is mostly invisible to the user. Not even the API server audit mechanism makes these events visible; only the object updates are visible. Controllers often use log output, though, when they react on events. There are two principled options to detect state change the event itself :. At the point in time the state change occurs, programming kubernetes download pdf, a handler is triggered—for example, from no pod to pod running. The state is checked at regular intervals and if certain conditions are met for example, pod runningthen a handler is triggered.
The latter is a form of polling. It does not scale well with the number of objects, and the latency of controllers noticing changes depends on the interval of polling and how fast the API server can answer. The former option is much more efficient with many objects. Hence, Kubernetes is based on events i. In the Kubernetes control plane, a number of components change objects on the API server, with each change leading to an event i.
We call these components event sources or event producers. In a distributed system there are many actors running in parallel, and events come in asynchronously in any order. Hence, we have to take a deeper look at how to cope with errors. In Figure you can see different strategies at work:. An example of an edge-triggered logic, which always gets the latest state i. In other words, the logic is edge-triggered but level-driven.
Strategy 1 does not cope well with missed events, whether because broken networking makes it lose events, or because the controller itself has bugs or some external cloud API was down.
Imagine that the replica set controller would replace pods only when they terminate. Missing events would mean that the replica set would always run programming kubernetes download pdf fewer pods because it never reconciles the whole state.
Strategy 2 recovers from programming kubernetes download pdf issues when another event is received because it implements its logic based on the programming kubernetes download pdf state in the cluster.
In the case of the replica set controller, it will always compare the specified replica count with the running pods in the cluster.
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LinOxide 2 6 Kubernetes - App Deployment Flow 64 7 Kubernetes – Auto scaling 66 8 Destroying Kubernetes Cluster and Pods 71 6. Deploying Kubernetes with Ansible 72 7. Provisioning Storage in Kubernetes 80 1 Kubernetes Persistent Volumes 81 2 Requesting storage 83 3 Using Claim as a Volume 84 4 Kubernetes and NFS 85 5 Kubernetes and iSCSI 87 8. Troubleshooting Kubernetes . Programming Kubernetes: Developing Cloud-Native Applications If you’re looking to develop native applications in Kubernetes, this Programming Kubernetes is your guide. Developers and AppOps administrators will learn how to build Kubernetes-native applications that interact directly with the API server to query or update the state of resources. Read Online Programming Kubernetes and Download Programming Kubernetes book full in PDF formats.
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