1 00:00:02,150 --> 00:00:04,550 So now that we had to look at the worker node, 2 00:00:04,550 --> 00:00:08,140 let's have another look at the master node. 3 00:00:08,140 --> 00:00:09,853 What's the master node doing? 4 00:00:11,383 --> 00:00:13,160 And which software is running in the master node? 5 00:00:13,160 --> 00:00:15,090 Well inside of the master node 6 00:00:15,090 --> 00:00:19,000 the most important thing, the most important service, 7 00:00:19,000 --> 00:00:20,920 the most important software you could say, 8 00:00:20,920 --> 00:00:24,690 which is up and running, is the API server. 9 00:00:24,690 --> 00:00:27,370 This is a simple service, which is running 10 00:00:27,370 --> 00:00:31,560 on the master node machine, which is the counterpoint 11 00:00:31,560 --> 00:00:35,780 for the kubelet services running on the worker nodes. 12 00:00:35,780 --> 00:00:37,460 So this is the counterpart 13 00:00:37,460 --> 00:00:40,883 for the communication between worker and master node. 14 00:00:41,890 --> 00:00:44,383 In addition to this API server, 15 00:00:44,383 --> 00:00:46,740 another service, which is installed and running 16 00:00:46,740 --> 00:00:50,260 on the master node machine, is a so-called scheduler, 17 00:00:50,260 --> 00:00:52,650 which basically is responsible 18 00:00:52,650 --> 00:00:57,360 for watching our pods and choosing worker nodes 19 00:00:57,360 --> 00:01:00,310 on which new pods should be created on, 20 00:01:00,310 --> 00:01:02,600 in case a new pod needs to be added 21 00:01:02,600 --> 00:01:06,260 because a pod got unhealthy and went down, 22 00:01:06,260 --> 00:01:09,950 or because of scaling, we needed to create a new pod. 23 00:01:09,950 --> 00:01:12,870 So this is responsible for actually then telling 24 00:01:12,870 --> 00:01:17,260 the API server what to tell the worker nodes. 25 00:01:17,260 --> 00:01:18,760 And we've got another service, 26 00:01:18,760 --> 00:01:21,210 which is to kube-controller manager, 27 00:01:21,210 --> 00:01:23,740 which in the end watches and controls 28 00:01:23,740 --> 00:01:25,740 the worker nodes overall, 29 00:01:25,740 --> 00:01:28,890 and which is responsible for ensuring 30 00:01:28,890 --> 00:01:31,790 that we get the correct number of pods up and running. 31 00:01:31,790 --> 00:01:34,310 And therefore, it of course works closely together 32 00:01:34,310 --> 00:01:37,500 with the scheduler and the API server. 33 00:01:37,500 --> 00:01:39,330 And there is a specific version of that 34 00:01:39,330 --> 00:01:41,120 kube-controller manager, 35 00:01:41,120 --> 00:01:43,700 which is the cloud-controller manager, 36 00:01:43,700 --> 00:01:45,630 which is doing the same thing, 37 00:01:45,630 --> 00:01:48,480 but which is cloud-provider specific. 38 00:01:48,480 --> 00:01:51,010 And which actually then knows how 39 00:01:51,010 --> 00:01:53,140 to tell that cloud provider, 40 00:01:53,140 --> 00:01:58,140 for example AWS or Microsoft Azure, what to do. 41 00:01:58,820 --> 00:02:00,750 So this cloud-controller manager 42 00:02:00,750 --> 00:02:03,940 basically just translates instructions 43 00:02:03,940 --> 00:02:08,840 to AWS or Azure or whatever you're using. 44 00:02:08,840 --> 00:02:13,210 The big cloud providers, which you are very likely to use 45 00:02:13,210 --> 00:02:16,470 in reality anyways, already got services 46 00:02:16,470 --> 00:02:19,160 which take all that away from you 47 00:02:19,160 --> 00:02:22,590 and where you therefore just needs to provide your 48 00:02:22,590 --> 00:02:27,053 kubernetes configuration and they do all the heavy lifting. 49 00:02:28,200 --> 00:02:30,860 And that's basically it, that's the big picture 50 00:02:30,860 --> 00:02:32,480 and the core architecture. 51 00:02:32,480 --> 00:02:33,560 And as I said, 52 00:02:33,560 --> 00:02:37,010 I'm aware that at this point you will probably still have 53 00:02:37,010 --> 00:02:39,670 a couple of questions related to that, 54 00:02:39,670 --> 00:02:43,570 but that will all become clearer over the next lectures 55 00:02:43,570 --> 00:02:46,323 and modules as we get our hands dirty.