WEBVTT 00:01.070 --> 00:04.130 Hello and welcome to this lecture. In this lecture 00:04.130 --> 00:10.910 we will talk about Kube Controller Manager. As we discussed earlier, the kube controller manager manages 00:10.970 --> 00:17.920 various controllers in Kubernetes. A controller is like an office or department within the master ship 00:17.980 --> 00:23.890 that have their own set of responsibilities. Such as an office for the Ships would be responsible for 00:23.890 --> 00:26.960 monitoring and taking necessary actions about the ships. 00:27.010 --> 00:32.110 Whenever a new ship arrives or when a ship leaves or gets destroyed another office could be one that 00:32.110 --> 00:37.700 manages the containers on the ships they take care of containers that are damaged or full of ships. 00:37.780 --> 00:45.480 So these officers are number 1, continuously on the lookout for the status of the ships and 2, take 00:45.520 --> 00:50.700 necessary actions to remediate the situation. In the kubernetes terms 00:50.880 --> 00:56.730 a controller is a process that continuously monitors the state of various components within the system 00:57.090 --> 01:01.670 and works towards bringing the whole system to the desired functioning state. 01:01.710 --> 01:07.770 For example the node controller is responsible for monitoring the status of the nodes and taking necessary 01:07.770 --> 01:10.610 actions to keep the application running. 01:10.620 --> 01:13.420 It does that through the kube-api server. 01:13.590 --> 01:17.550 The node controller checks the status of the nodes every 5 seconds. 01:17.550 --> 01:22.800 That way the node controller can monitor the health of the nodes if it stops receiving heartbeat from 01:22.800 --> 01:31.460 a node the node is marked as unreachable but it waits for 40 seconds before marking it unreachable after 01:31.460 --> 01:38.280 a node is marked unreachable it gives it five minutes to come back up if it doesn’t, it removes the 01:38.280 --> 01:42.890 PODs assigned to that node and provisions them on the healthy ones. 01:42.990 --> 01:48.980 If the PODs are part of a replica set the next controller is the replication controller. 01:49.030 --> 01:54.520 It is responsible for monitoring the status of replica sets and ensuring that the desired number of 01:54.520 --> 01:58.240 PODs are available at all times within the set. 01:58.300 --> 02:01.800 If a pod dies it creates another one. 02:01.850 --> 02:04.960 Now those were just two examples of controllers. 02:05.000 --> 02:08.990 There are many more such controllers available within kubernetes. 02:08.990 --> 02:15.180 Whatever concepts we have seen so far in kubernetes such as deployments, Services, namespaces, 02:15.180 --> 02:21.890 persistent volumes and whatever intelligence is built into these constructs it is implemented through 02:21.890 --> 02:23.740 these various controllers. 02:23.900 --> 02:29.240 As you can imagine this is kind of the brain behind a lot of things in kubernetes. 02:29.480 --> 02:34.330 Now how do you see these controllers and where are they located in your cluster. 02:34.380 --> 02:39.460 They're all packaged into a single process known as kubernetes controller manager. 02:39.670 --> 02:45.150 When you install the kubernetes controller manager the different controllers get installed as well. 02:45.250 --> 02:47.140 So how do you install and view the kubernetes 02:47.140 --> 02:53.200 Controller manager download the kube-controller-manager from the kubernetes release page. Extract it and 02:53.200 --> 02:54.550 run it as a service. 02:54.700 --> 03:01.060 When you run it as you can see there are a list of options provided this is where you provide additional 03:01.060 --> 03:03.590 options to customize your controller. 03:03.610 --> 03:08.810 Remember some of the default settings for node controller we discussed earlier such as the node monitor 03:08.810 --> 03:12.490 period the grace period and the eviction timeout. 03:12.490 --> 03:15.700 These go in here as options. 03:15.700 --> 03:20.890 There is an additional option called controllers that you can use to specify which controllers to enable. 03:21.490 --> 03:22.390 By default 03:22.390 --> 03:27.110 all of them are enabled but you can choose to enable a select few. 03:27.210 --> 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 03:32.890 --> 03:33.190 look at. 03:34.400 --> 03:37.370 So how do you view the Kube-controller-manager server options? 03:37.370 --> 03:39.540 Again it depends on how you set up your cluster. 03:39.560 --> 03:45.170 If you set it up with kubeadm tool, kubeadm deploys the kube-controller-manager as a pod in the 03:45.170 --> 03:51.350 kube-system namespace on the master node. You can see the options within the pod definition file located 03:51.350 --> 03:57.980 at etc kubernetes manifests folder. In a non-kubeadm setup, you can inspect the options by viewing 03:57.980 --> 04:02.460 the kube-controller-manager service located at the services directory. 04:02.510 --> 04:07.760 You can also see the running process and the effective options by listing the process on the master 04:07.760 --> 04:10.610 node and searching for kube-controller-manager. 04:11.430 --> 04:14.910 Well that's it for this lecture and I will see you in the next.