1 00:00:01,070 --> 00:00:04,130 Hello and welcome to this lecture. In this lecture 2 00:00:04,130 --> 00:00:10,910 we will talk about Kube Controller Manager. As we discussed earlier, the kube controller manager manages 3 00:00:10,970 --> 00:00:17,920 various controllers in Kubernetes. A controller is like an office or department within the master ship 4 00:00:17,980 --> 00:00:23,890 that have their own set of responsibilities. Such as an office for the Ships would be responsible for 5 00:00:23,890 --> 00:00:26,960 monitoring and taking necessary actions about the ships. 6 00:00:27,010 --> 00:00:32,110 Whenever a new ship arrives or when a ship leaves or gets destroyed another office could be one that 7 00:00:32,110 --> 00:00:37,700 manages the containers on the ships they take care of containers that are damaged or full of ships. 8 00:00:37,780 --> 00:00:45,480 So these officers are number 1, continuously on the lookout for the status of the ships and 2, take 9 00:00:45,520 --> 00:00:50,700 necessary actions to remediate the situation. In the kubernetes terms 10 00:00:50,880 --> 00:00:56,730 a controller is a process that continuously monitors the state of various components within the system 11 00:00:57,090 --> 00:01:01,670 and works towards bringing the whole system to the desired functioning state. 12 00:01:01,710 --> 00:01:07,770 For example the node controller is responsible for monitoring the status of the nodes and taking necessary 13 00:01:07,770 --> 00:01:10,610 actions to keep the application running. 14 00:01:10,620 --> 00:01:13,420 It does that through the kube-api server. 15 00:01:13,590 --> 00:01:17,550 The node controller checks the status of the nodes every 5 seconds. 16 00:01:17,550 --> 00:01:22,800 That way the node controller can monitor the health of the nodes if it stops receiving heartbeat from 17 00:01:22,800 --> 00:01:31,460 a node the node is marked as unreachable but it waits for 40 seconds before marking it unreachable after 18 00:01:31,460 --> 00:01:38,280 a node is marked unreachable it gives it five minutes to come back up if it doesn’t, it removes the 19 00:01:38,280 --> 00:01:42,890 PODs assigned to that node and provisions them on the healthy ones. 20 00:01:42,990 --> 00:01:48,980 If the PODs are part of a replica set the next controller is the replication controller. 21 00:01:49,030 --> 00:01:54,520 It is responsible for monitoring the status of replica sets and ensuring that the desired number of 22 00:01:54,520 --> 00:01:58,240 PODs are available at all times within the set. 23 00:01:58,300 --> 00:02:01,800 If a pod dies it creates another one. 24 00:02:01,850 --> 00:02:04,960 Now those were just two examples of controllers. 25 00:02:05,000 --> 00:02:08,990 There are many more such controllers available within kubernetes. 26 00:02:08,990 --> 00:02:15,180 Whatever concepts we have seen so far in kubernetes such as deployments, Services, namespaces, 27 00:02:15,180 --> 00:02:21,890 persistent volumes and whatever intelligence is built into these constructs it is implemented through 28 00:02:21,890 --> 00:02:23,740 these various controllers. 29 00:02:23,900 --> 00:02:29,240 As you can imagine this is kind of the brain behind a lot of things in kubernetes. 30 00:02:29,480 --> 00:02:34,330 Now how do you see these controllers and where are they located in your cluster. 31 00:02:34,380 --> 00:02:39,460 They're all packaged into a single process known as kubernetes controller manager. 32 00:02:39,670 --> 00:02:45,150 When you install the kubernetes controller manager the different controllers get installed as well. 33 00:02:45,250 --> 00:02:47,140 So how do you install and view the kubernetes 34 00:02:47,140 --> 00:02:53,200 Controller manager download the kube-controller-manager from the kubernetes release page. Extract it and 35 00:02:53,200 --> 00:02:54,550 run it as a service. 36 00:02:54,700 --> 00:03:01,060 When you run it as you can see there are a list of options provided this is where you provide additional 37 00:03:01,060 --> 00:03:03,590 options to customize your controller. 38 00:03:03,610 --> 00:03:08,810 Remember some of the default settings for node controller we discussed earlier such as the node monitor 39 00:03:08,810 --> 00:03:12,490 period the grace period and the eviction timeout. 40 00:03:12,490 --> 00:03:15,700 These go in here as options. 41 00:03:15,700 --> 00:03:20,890 There is an additional option called controllers that you can use to specify which controllers to enable. 42 00:03:21,490 --> 00:03:22,390 By default 43 00:03:22,390 --> 00:03:27,110 all of them are enabled but you can choose to enable a select few. 44 00:03:27,210 --> 00:03:32,890 So in case any of your controllers don't seem to work or exist this would be a good starting point to 45 00:03:32,890 --> 00:03:33,190 look at. 46 00:03:34,400 --> 00:03:37,370 So how do you view the Kube-controller-manager server options? 47 00:03:37,370 --> 00:03:39,540 Again it depends on how you set up your cluster. 48 00:03:39,560 --> 00:03:45,170 If you set it up with kubeadm tool, kubeadm deploys the kube-controller-manager as a pod in the 49 00:03:45,170 --> 00:03:51,350 kube-system namespace on the master node. You can see the options within the pod definition file located 50 00:03:51,350 --> 00:03:57,980 at etc kubernetes manifests folder. In a non-kubeadm setup, you can inspect the options by viewing 51 00:03:57,980 --> 00:04:02,460 the kube-controller-manager service located at the services directory. 52 00:04:02,510 --> 00:04:07,760 You can also see the running process and the effective options by listing the process on the master 53 00:04:07,760 --> 00:04:10,610 node and searching for kube-controller-manager. 54 00:04:11,430 --> 00:04:14,910 Well that's it for this lecture and I will see you in the next.