1 00:00:00,770 --> 00:00:03,320 Hello and welcome to this lecture in this lecture. 2 00:00:03,320 --> 00:00:07,230 In this lecture we will talk about the Kube-API server in kubernetes. 3 00:00:07,460 --> 00:00:14,660 Earlier we discussed that the Kube-api server is the primary management component in kubernetes. When 4 00:00:14,660 --> 00:00:21,710 you run a kubectl command, the kubectl utility is infact reaching to the kube-apiserver. 5 00:00:21,710 --> 00:00:28,010 The kube-api server first authenticates the request and validates it. It then retrieves the data from the 6 00:00:28,010 --> 00:00:31,910 ETCD cluster and responds back with the requested information. 7 00:00:32,930 --> 00:00:35,580 You don’t really need to use the kubectl command line. 8 00:00:35,660 --> 00:00:42,650 Instead, you could also invoke the API directly by sending a post request like this let's look at an 9 00:00:42,650 --> 00:00:50,950 example of creating a pod when you do that as before the request is authenticated first and then validated. 10 00:00:51,110 --> 00:00:57,980 In this case, the API server creates a POD object without assigning it to a node, updates the information 11 00:00:57,980 --> 00:01:02,000 in the ETCD server updates the user that the POD has been created. 12 00:01:03,720 --> 00:01:10,170 The scheduler continuously monitors the API server and realizes that there is a new pod with no node 13 00:01:10,170 --> 00:01:16,500 assigned the scheduler identifies the right node to place the new POD on and communicates that back 14 00:01:16,500 --> 00:01:18,220 to the kube-apiserver. 15 00:01:18,480 --> 00:01:25,350 The API server then updates the information in the ETCD cluster. The API server then passes that information 16 00:01:25,350 --> 00:01:28,060 to the kubelet in appropriate worker node. 17 00:01:28,520 --> 00:01:34,200 The kubelet then creates the POD on the node and instructs the container runtime engine to deploy the 18 00:01:34,200 --> 00:01:36,000 application image. 19 00:01:36,060 --> 00:01:43,110 Once done, the kubelet updates the status back to the API server and the API server then updates the 20 00:01:43,110 --> 00:01:50,810 data back in the ETCD cluster. A similar pattern is followed every time a change is requested. 21 00:01:50,810 --> 00:01:56,560 The kube-apiserver is at the center of all the different tasks that needs to be performed to make a 22 00:01:56,560 --> 00:01:58,370 change in the cluster. 23 00:01:58,370 --> 00:02:04,430 To summarize, the kube-api server is responsible for Authenticating and validating requests, retrieving 24 00:02:04,430 --> 00:02:07,090 and updating data in ETCD data store, 25 00:02:07,130 --> 00:02:13,460 in fact, kube-api server is the only component that interacts directly with the etcd datastore. 26 00:02:13,460 --> 00:02:16,760 The other components such as the scheduler, kube-controller-manager & kubelet 27 00:02:16,760 --> 00:02:21,860 uses the API server to perform updates in the cluster in their respective areas. 28 00:02:23,090 --> 00:02:28,970 If you bootstrapped your cluster using kubeadm tool then you don't need to know this but if you are 29 00:02:28,970 --> 00:02:34,670 setting up the hard way, then kube-apiserver is available as a binary in the kubernetes release 30 00:02:34,670 --> 00:02:40,820 page. Download it and configure it to run as a service on your kubernetes master node. 31 00:02:41,120 --> 00:02:47,520 The kube-api server is run with a lot of parameters as you can see here. Throughout this section 32 00:02:47,630 --> 00:02:52,410 we are going to take a peak at how to install and configure these individual components of the kubernetes 33 00:02:52,430 --> 00:02:53,960 architecture. 34 00:02:53,960 --> 00:02:59,630 You don't have to understand all of the options right now but I think having a high level understanding 35 00:02:59,750 --> 00:03:05,960 on some of these now will make it easier later when we configure the whole cluster and all of its components 36 00:03:06,170 --> 00:03:07,730 from scratch. 37 00:03:07,730 --> 00:03:13,040 The kubernetes architecture consists of a lot of different components working with each other, talking 38 00:03:13,040 --> 00:03:19,350 to each other in many different ways so they all need to know where the other components are. 39 00:03:19,490 --> 00:03:24,920 There are different modes of authentication, authorization, encryption and security. And that’s why you 40 00:03:24,920 --> 00:03:30,590 have so many options when we go through the relevant section in the course we will pull up this file 41 00:03:30,620 --> 00:03:32,390 and look at the relevant options. 42 00:03:32,510 --> 00:03:35,850 For now we will look at a few important ones. 43 00:03:35,960 --> 00:03:40,700 A lot of them are certificates that are used to secure the connectivity between different components. 44 00:03:40,730 --> 00:03:46,070 We look at these certificates in more detail when we go through the SSL/TLS certificates lecture later 45 00:03:46,070 --> 00:03:47,510 in this course. 46 00:03:47,510 --> 00:03:51,410 There is a whole section just for it. So we will get rid of them for now. 47 00:03:51,410 --> 00:03:56,300 But just remember all of the various components we are going to look at in this section will have certificates 48 00:03:56,390 --> 00:04:02,880 associated with them. The option ETCD-servers is where you specify the location of the ETCD servers. 49 00:04:02,900 --> 00:04:06,290 This is how the kube-api server connects to the etcd servers. 50 00:04:06,800 --> 00:04:10,940 So how do you view the kube-api server options in an existing cluster 51 00:04:10,970 --> 00:04:13,560 It depends on how you set up your cluster. 52 00:04:13,610 --> 00:04:19,070 . If you set it up with kubeadm tool, kubeadm deploys the kube-api server as a pod in the kube- 53 00:04:19,070 --> 00:04:25,130 system namespace on the master node you can see the options within the pod definition file located at 54 00:04:25,430 --> 00:04:32,990 etc kubernetes manifests folder. etc kubernetes manifests folder. 55 00:04:32,990 --> 00:04:41,270 kube-apiserver service located at /etc/systemd/system/kube-apiserver.service.You can also see 56 00:04:41,270 --> 00:04:46,490 the running process and the effective options by listing the process on the master node and searching 57 00:04:46,490 --> 00:04:48,680 for kube-apiserver. 58 00:04:48,680 --> 00:04:50,300 Well that's it for this lecture.