1 00:00:02,330 --> 00:00:03,730 So let's take a closer look 2 00:00:03,730 --> 00:00:06,000 at these Worker Nodes now. 3 00:00:06,000 --> 00:00:07,760 A Worker Node, as I mentioned, 4 00:00:07,760 --> 00:00:10,870 is simply our machine, a computer, 5 00:00:10,870 --> 00:00:14,810 an ec2 instance, for example, running somewhere. 6 00:00:14,810 --> 00:00:17,220 And the Worker Node is managed 7 00:00:17,220 --> 00:00:19,553 by the Master Node, as I explained. 8 00:00:20,610 --> 00:00:22,620 Now, inside of that Worker Node, 9 00:00:22,620 --> 00:00:25,320 we have our Pods. 10 00:00:25,320 --> 00:00:28,290 And a Pod simply hosts one or more 11 00:00:28,290 --> 00:00:30,740 application containers and all their 12 00:00:30,740 --> 00:00:33,680 resources belonging to these containers. 13 00:00:33,680 --> 00:00:35,410 For example, the configuration 14 00:00:35,410 --> 00:00:37,290 to run the containers correctly, 15 00:00:37,290 --> 00:00:39,630 but also things like volumes. 16 00:00:39,630 --> 00:00:43,320 And the Pods themselves are managed by Kubernetes, 17 00:00:43,320 --> 00:00:45,270 again, by this Master Node. 18 00:00:45,270 --> 00:00:46,960 So, Kubernetes can, for example, 19 00:00:46,960 --> 00:00:49,080 create or delete Pods. 20 00:00:49,080 --> 00:00:51,120 And when a Pod is deleted, 21 00:00:51,120 --> 00:00:54,010 the Pod internally is then able to run 22 00:00:54,010 --> 00:00:57,430 and manage the Container that belongs to the Pod. 23 00:00:57,430 --> 00:01:00,220 And, of course, you can have one Container in a Pod, 24 00:01:00,220 --> 00:01:02,180 but if you have multiple Containers, 25 00:01:02,180 --> 00:01:04,650 which need to work together closely, 26 00:01:04,650 --> 00:01:06,730 you could also have multiple Containers 27 00:01:06,730 --> 00:01:08,330 inside of a Pod. 28 00:01:08,330 --> 00:01:11,670 And then any additional resources that might be needed, 29 00:01:11,670 --> 00:01:14,550 like for example, a Volume, so some space on a 30 00:01:14,550 --> 00:01:18,660 hard drive which the Containers can talk to. 31 00:01:18,660 --> 00:01:21,850 And as I also mentioned, the idea typically is 32 00:01:21,850 --> 00:01:23,690 that you have more than one Pod 33 00:01:23,690 --> 00:01:26,780 running on a given Worker Node. 34 00:01:26,780 --> 00:01:29,810 Now, that can be a copy of another Pod, 35 00:01:29,810 --> 00:01:32,290 in case you're scaling it up and you want to have 36 00:01:32,290 --> 00:01:34,920 multiple instances off one and the same 37 00:01:34,920 --> 00:01:37,670 Container up and running to distribute 38 00:01:37,670 --> 00:01:39,740 incoming traffic, for example. 39 00:01:39,740 --> 00:01:42,560 But it can also be a Pod with a totally different 40 00:01:42,560 --> 00:01:46,140 Container inside of it to do a totally different task. 41 00:01:46,140 --> 00:01:49,090 Because the Worker Node is not task specific, 42 00:01:49,090 --> 00:01:52,810 the Worker Node, it's really important to keep this in mind, 43 00:01:52,810 --> 00:01:55,480 is just your computer, your machine. 44 00:01:55,480 --> 00:01:58,410 It's just a machine somewhere on the internet 45 00:01:58,410 --> 00:02:00,850 with a certain amount of CPU and memory, 46 00:02:00,850 --> 00:02:03,420 and, therefore, you can of course run totally 47 00:02:03,420 --> 00:02:06,300 different Containers and tasks on it, 48 00:02:06,300 --> 00:02:08,210 just as you can run totally different 49 00:02:08,210 --> 00:02:11,240 Containers on our own development machine. 50 00:02:11,240 --> 00:02:13,050 With the "docker run" command, 51 00:02:13,050 --> 00:02:15,660 I can run as many Containers based on 52 00:02:15,660 --> 00:02:18,490 as many different images as I want. 53 00:02:18,490 --> 00:02:21,000 And we actually did this throughout the course, 54 00:02:21,000 --> 00:02:22,920 also with "docker compose". 55 00:02:22,920 --> 00:02:25,340 We definitely had a backend, a frontend, 56 00:02:25,340 --> 00:02:29,750 and a database container running all on our local machine. 57 00:02:29,750 --> 00:02:32,100 And it's basically the same with a Worker Node. 58 00:02:32,100 --> 00:02:33,949 It's just on our local machine, but some machine 59 00:02:33,949 --> 00:02:37,530 out there in the internet offered by some 60 00:02:37,530 --> 00:02:39,093 cloud provider, typically. 61 00:02:39,980 --> 00:02:42,380 Now on this Worker Node, we then all don't just 62 00:02:42,380 --> 00:02:45,570 have these Pods, but also some additional software. 63 00:02:45,570 --> 00:02:48,690 For example, Docker needs to be installed there, 64 00:02:48,690 --> 00:02:51,720 because Docker, of course, is required by the Pods 65 00:02:51,720 --> 00:02:54,270 to create and run the Containers. 66 00:02:54,270 --> 00:02:57,270 We then also have another piece of software 67 00:02:57,270 --> 00:03:00,270 running there, which is called a kubelet, 68 00:03:00,270 --> 00:03:03,000 which is basically the communication device 69 00:03:03,000 --> 00:03:05,650 between the Worker Node and the Master Node. 70 00:03:05,650 --> 00:03:08,596 So, it's basically a software service running 71 00:03:08,596 --> 00:03:11,220 on that machine, on the Worker Node machine, 72 00:03:11,220 --> 00:03:13,910 which does the actual communication with the 73 00:03:13,910 --> 00:03:17,160 Master Node, so that the Master Node is able to 74 00:03:17,160 --> 00:03:20,320 control the Pods on this Worker Node. 75 00:03:20,320 --> 00:03:22,900 And, we've got this proxy service running, 76 00:03:22,900 --> 00:03:26,600 which is responsible for handling incoming and outgoing 77 00:03:26,600 --> 00:03:30,940 traffic to insure that everything is working as desired, 78 00:03:30,940 --> 00:03:34,550 and only allowed traffic is able to reach the Pods, 79 00:03:34,550 --> 00:03:38,023 and only allowed traffic is able to leave the Worker Node. 80 00:03:39,330 --> 00:03:41,380 And that is the Worker Node. 81 00:03:41,380 --> 00:03:43,600 That's a closer look at the Worker Node 82 00:03:43,600 --> 00:03:46,090 and what's running on there. 83 00:03:46,090 --> 00:03:49,050 And the great thing is that with Kubernetes, 84 00:03:49,050 --> 00:03:52,450 you just need to define the desired end state, 85 00:03:52,450 --> 00:03:55,940 and if you're then using a cloud provider like AWS, 86 00:03:55,940 --> 00:03:59,430 they have services which allow you to provide 87 00:03:59,430 --> 00:04:03,450 this Kubernetes definition, and then AWS will 88 00:04:03,450 --> 00:04:06,870 set up all the instances and install all the 89 00:04:06,870 --> 00:04:08,860 required software for you. 90 00:04:08,860 --> 00:04:10,960 So you don't have to deal with that. 91 00:04:10,960 --> 00:04:13,180 You just have to know what's happening there, 92 00:04:13,180 --> 00:04:16,310 because as a developer, you should always know 93 00:04:16,310 --> 00:04:19,452 what your code, and what your configuration is doing.