1 00:00:02,210 --> 00:00:03,600 Now up to this point, 2 00:00:03,600 --> 00:00:07,980 we always had a look at this demo Node.js application 3 00:00:07,980 --> 00:00:10,510 which spin up that web server, 4 00:00:10,510 --> 00:00:15,290 and indeed web development and running web servers 5 00:00:15,290 --> 00:00:18,637 and other processes that deal with incoming requests 6 00:00:18,637 --> 00:00:23,550 and so on, that is the main selling point of Docker. 7 00:00:23,550 --> 00:00:27,140 That is the use case it's getting used for the most 8 00:00:27,140 --> 00:00:29,610 no matter if you then use Node.js 9 00:00:29,610 --> 00:00:31,640 for building that web service 10 00:00:31,640 --> 00:00:36,080 or if you use PHP, Python, whatever it is. 11 00:00:36,080 --> 00:00:40,730 But it's not just that, Docker is not restricted to that, 12 00:00:40,730 --> 00:00:44,090 and attached you find another example. 13 00:00:44,090 --> 00:00:46,840 A very simple Python application 14 00:00:46,840 --> 00:00:48,720 if you wanna call it like this 15 00:00:48,720 --> 00:00:51,844 which is built for Python version three 16 00:00:51,844 --> 00:00:54,360 and that's important here, 17 00:00:54,360 --> 00:00:59,360 which does not create any web server or anything like that. 18 00:00:59,940 --> 00:01:03,730 Instead of this application, in case you don't know Python 19 00:01:03,730 --> 00:01:08,320 fetches two user inputs a min and a max number, 20 00:01:08,320 --> 00:01:12,300 stores those in variables, runs a quick check, 21 00:01:12,300 --> 00:01:15,780 seeing whether the min number really is smaller 22 00:01:15,780 --> 00:01:17,030 than the max number, 23 00:01:17,030 --> 00:01:20,710 and then we calculate a random value here 24 00:01:20,710 --> 00:01:22,473 and output that value. 25 00:01:23,460 --> 00:01:27,490 Now you can install Python on your system to run this 26 00:01:27,490 --> 00:01:30,920 or you put it into a Docker image and container, 27 00:01:30,920 --> 00:01:32,850 and that's what I wanna do here 28 00:01:32,850 --> 00:01:36,500 for two main reasons, of course, to show you 29 00:01:36,500 --> 00:01:40,700 that Docker is not just about node and web servers 30 00:01:40,700 --> 00:01:44,840 I said this before, but I also wanna show it to you. 31 00:01:44,840 --> 00:01:48,610 But the second reason is related to what we learned 32 00:01:48,610 --> 00:01:52,670 in the last lecture attached and detached containers. 33 00:01:52,670 --> 00:01:55,723 So containers running in the front and in the background. 34 00:01:56,570 --> 00:02:00,480 Here, this will play a greater role because this app 35 00:02:00,480 --> 00:02:04,230 actually needs the user to interact with the app. 36 00:02:04,230 --> 00:02:08,020 Running this example here in background 37 00:02:08,020 --> 00:02:12,880 won't really work, but step-by-step, let's Dockerize this 38 00:02:12,880 --> 00:02:15,100 and of course, if you feel like this 39 00:02:15,100 --> 00:02:17,710 definitely also try it on your own. 40 00:02:17,710 --> 00:02:20,380 Otherwise you can now follow along with me 41 00:02:20,380 --> 00:02:23,913 as I will write a Docker file for this application. 42 00:02:24,910 --> 00:02:28,113 Now, how could we run this with Docker? 43 00:02:29,760 --> 00:02:32,900 Well, in the end I wanna build a custom image 44 00:02:32,900 --> 00:02:36,630 which uses Python as a base image 45 00:02:36,630 --> 00:02:40,360 so that I can copy my code, the Python code file here 46 00:02:40,360 --> 00:02:44,770 into that image and executed with the help of Python. 47 00:02:44,770 --> 00:02:49,650 Now on Docker hub I can therefore search for Python 48 00:02:49,650 --> 00:02:53,350 and will find official Python images here 49 00:02:53,350 --> 00:02:55,020 and that of course means 50 00:02:55,020 --> 00:02:59,993 that here we can absolutely use Python as base image. 51 00:03:01,160 --> 00:03:05,460 So we wanna use the Python base image as a next step, 52 00:03:05,460 --> 00:03:07,740 I also wanna set a working directory 53 00:03:07,740 --> 00:03:09,850 and I'll again, set this to app 54 00:03:09,850 --> 00:03:11,533 this of course is up to you. 55 00:03:13,020 --> 00:03:14,410 Now as a next step 56 00:03:14,410 --> 00:03:16,830 I wanna copy in my code files 57 00:03:16,830 --> 00:03:20,470 or in this case, the single code file which I have here 58 00:03:20,470 --> 00:03:22,410 still I can use copy dot 59 00:03:22,410 --> 00:03:24,940 and copy everything in the local folder 60 00:03:24,940 --> 00:03:27,640 which essentially is the Python file 61 00:03:27,640 --> 00:03:29,563 therefore into this app folder. 62 00:03:31,600 --> 00:03:35,320 Now, as a last step we can add the command here 63 00:03:35,320 --> 00:03:38,900 that should be executed when this container is started 64 00:03:38,900 --> 00:03:42,120 and here, I wanna use the Python executable 65 00:03:42,120 --> 00:03:45,720 which will be available, thanks to the Python image 66 00:03:45,720 --> 00:03:49,410 and run the RNG dot PY file with it. 67 00:03:49,410 --> 00:03:53,260 That's my command with which this container 68 00:03:53,260 --> 00:03:55,150 should start when we started 69 00:03:57,280 --> 00:03:59,773 and that could be our Docker file here. 70 00:04:00,670 --> 00:04:03,070 Now with that created 71 00:04:03,070 --> 00:04:08,070 we of course can run Docker build dot to build this image, 72 00:04:10,870 --> 00:04:13,570 and since this is the first time I'm building this 73 00:04:13,570 --> 00:04:17,970 it will, of course also download this Python base image 74 00:04:17,970 --> 00:04:21,529 and they offered this initial building takes a bit longer. 75 00:04:21,529 --> 00:04:24,130 So let me wait for this to finish 76 00:04:25,240 --> 00:04:28,260 and now with that done, this image is built. 77 00:04:28,260 --> 00:04:31,570 Now we can use the image ID here 78 00:04:31,570 --> 00:04:35,650 to then bring up a container by running Docker run. 79 00:04:35,650 --> 00:04:38,820 Now here, I don't wanna publish any port 80 00:04:38,820 --> 00:04:41,210 because we're not exposing any port here, 81 00:04:41,210 --> 00:04:43,630 it's not a network based application 82 00:04:43,630 --> 00:04:45,670 so no needs to do that 83 00:04:45,670 --> 00:04:47,643 instead I really just wanna run it. 84 00:04:48,700 --> 00:04:53,480 And if I run it like this though I get an error here. 85 00:04:53,480 --> 00:04:55,920 To be precise, I see some output here 86 00:04:55,920 --> 00:04:58,200 because with Docker run as you learned 87 00:04:58,200 --> 00:05:01,080 by default we start in attached mode, 88 00:05:01,080 --> 00:05:04,940 but I don't see anything else besides this error message 89 00:05:04,940 --> 00:05:08,530 I'm not able to interact with this running container 90 00:05:08,530 --> 00:05:11,820 and with the application running into container 91 00:05:11,820 --> 00:05:15,450 and the reason for that is that by default, 92 00:05:15,450 --> 00:05:17,350 yes, when using Docker run 93 00:05:17,350 --> 00:05:19,730 we are attached to the container 94 00:05:19,730 --> 00:05:24,150 so we can listen to output printed by the container 95 00:05:24,150 --> 00:05:25,760 but we're not attached to it 96 00:05:25,760 --> 00:05:29,540 in the sense of being able to enter anything, 97 00:05:29,540 --> 00:05:33,090 we can't input anything into the container 98 00:05:33,090 --> 00:05:36,090 or into the application running into container 99 00:05:36,090 --> 00:05:39,510 and that is something I need to fix here. 100 00:05:39,510 --> 00:05:42,577 Now for that let's execute dash, dash help 101 00:05:42,577 --> 00:05:45,280 the dash dash help flag on Docker run 102 00:05:45,280 --> 00:05:49,700 and see which useful configuration options we got here. 103 00:05:49,700 --> 00:05:53,420 And here we actually have two options that will help us. 104 00:05:53,420 --> 00:05:56,330 The first one is the dash I option 105 00:05:56,330 --> 00:06:01,280 which allows to launch this container in interactive mode, 106 00:06:01,280 --> 00:06:04,070 you could also use dash dash interactive instead 107 00:06:04,070 --> 00:06:07,710 but of course, dash I is shorter, so we'll use that 108 00:06:07,710 --> 00:06:11,580 this keeps standard input open even if not attached 109 00:06:11,580 --> 00:06:14,640 which means we will be able to input 110 00:06:14,640 --> 00:06:16,660 something in a container. 111 00:06:16,660 --> 00:06:20,840 However, typically we combine this with dash T 112 00:06:20,840 --> 00:06:22,780 this allocates a pseudo TTY 113 00:06:24,090 --> 00:06:27,540 and in the end this means it creates a terminal 114 00:06:27,540 --> 00:06:31,870 and therefore if you combine the I and the T flag 115 00:06:31,870 --> 00:06:34,250 we are able to input something 116 00:06:34,250 --> 00:06:36,670 so the container will listen for our input 117 00:06:36,670 --> 00:06:40,110 and we'll also get a terminal exposed by the container 118 00:06:40,110 --> 00:06:43,293 which is actually the device where we enter the input. 119 00:06:44,770 --> 00:06:48,210 So with that, we can rerun this container 120 00:06:48,210 --> 00:06:53,210 but now by adding the dash I and the dash T flag 121 00:06:53,220 --> 00:06:56,860 and we can also combine this to just one flag dash IT 122 00:06:58,510 --> 00:07:01,560 and with this now you see it doesn't crash 123 00:07:01,560 --> 00:07:04,140 because now it's getting the input it needs 124 00:07:04,140 --> 00:07:07,820 and we can now type something here in our terminal 125 00:07:07,820 --> 00:07:10,940 which communicates with this pseudo terminal 126 00:07:10,940 --> 00:07:12,700 exposed by the container. 127 00:07:12,700 --> 00:07:15,090 Which then in turn, also is connected 128 00:07:15,090 --> 00:07:19,053 to the container process that listens for user input. 129 00:07:19,910 --> 00:07:22,930 So here I can then enter a min and a max number 130 00:07:22,930 --> 00:07:26,183 and I get back this random number. 131 00:07:27,230 --> 00:07:30,470 And there after you see the container shuts down 132 00:07:30,470 --> 00:07:32,070 it's no longer running 133 00:07:32,070 --> 00:07:35,840 we see it with dash A but that is okay here. 134 00:07:35,840 --> 00:07:40,213 We could now restarted with Docker start using that name 135 00:07:43,370 --> 00:07:45,500 and it would be running again. 136 00:07:45,500 --> 00:07:48,530 However, of course, now you see we have a problem 137 00:07:48,530 --> 00:07:53,500 now, since Docker starts in detached mode by default 138 00:07:53,500 --> 00:07:55,873 we can't communicate with the container. 139 00:07:57,000 --> 00:07:58,750 So how can we now deal with that? 140 00:07:58,750 --> 00:08:00,890 If we restarted the container. 141 00:08:00,890 --> 00:08:02,590 Well, there are two ways, 142 00:08:02,590 --> 00:08:05,430 for one, let me stop this again real quick 143 00:08:05,430 --> 00:08:08,020 we can also restart the container 144 00:08:08,020 --> 00:08:09,940 in attached mode, of course. 145 00:08:09,940 --> 00:08:14,940 So if I do that Docker start and I add dash A here 146 00:08:15,560 --> 00:08:17,420 we start an attached mode 147 00:08:17,420 --> 00:08:20,750 and now we can also enter something here 148 00:08:20,750 --> 00:08:24,840 but only once, there after it behaves strangely. 149 00:08:24,840 --> 00:08:27,030 So that doesn't look right. 150 00:08:27,030 --> 00:08:28,970 So let me cancel this 151 00:08:30,150 --> 00:08:33,020 and then also stop this container again 152 00:08:33,020 --> 00:08:37,809 and show you the other way of restarting this container 153 00:08:37,809 --> 00:08:40,460 and being able to input something again. 154 00:08:40,460 --> 00:08:42,970 Because if we have a look at Docker start 155 00:08:42,970 --> 00:08:46,660 configuration options, you'll see we don't just have dash A 156 00:08:46,660 --> 00:08:48,130 for listening to output 157 00:08:48,130 --> 00:08:53,130 but all the dash I to again, be able to input something 158 00:08:53,360 --> 00:08:54,920 into the container. 159 00:08:54,920 --> 00:08:57,580 Now here will not need the dash T flag 160 00:08:57,580 --> 00:08:59,840 because that was still memorized, 161 00:08:59,840 --> 00:09:03,200 if we ran the container originally with that flag, 162 00:09:03,200 --> 00:09:05,610 with the Docker run command which we did, 163 00:09:05,610 --> 00:09:08,390 but I need to kind of re-emphasize 164 00:09:08,390 --> 00:09:11,623 that when I restarted here, I also again wanna listen. 165 00:09:12,730 --> 00:09:16,030 So now, I can again start this container 166 00:09:16,030 --> 00:09:19,230 but now also add dash A and dash I 167 00:09:19,230 --> 00:09:22,820 and now I can enter a min and a max number 168 00:09:22,820 --> 00:09:25,660 and I get back my random number. 169 00:09:25,660 --> 00:09:27,830 So this is how we can now restart this 170 00:09:27,830 --> 00:09:30,650 and still attach us to the container 171 00:09:30,650 --> 00:09:32,900 but not just in the listen only mode 172 00:09:32,900 --> 00:09:36,723 but also in the I want to input something mode. 173 00:09:37,940 --> 00:09:40,170 And this hopefully again, shows you the idea 174 00:09:40,170 --> 00:09:42,430 behind being attached or detached 175 00:09:42,430 --> 00:09:45,120 and why some applications like this one 176 00:09:45,120 --> 00:09:47,690 might need us to be attached 177 00:09:47,690 --> 00:09:51,920 not just for listening to output, but also to provide input 178 00:09:51,920 --> 00:09:55,240 because Docker is not just about web servers 179 00:09:55,240 --> 00:09:59,720 and web applications and long running processes. 180 00:09:59,720 --> 00:10:02,830 Docker can also be used to dockerize 181 00:10:02,830 --> 00:10:05,950 simple utility applications like this 182 00:10:05,950 --> 00:10:08,280 which need input and provide some output 183 00:10:08,280 --> 00:10:10,340 and eventually might be done. 184 00:10:10,340 --> 00:10:13,840 That is also something you can use Docker for, 185 00:10:13,840 --> 00:10:17,513 Well, and that is how you can use Docker for this. 186 00:10:18,350 --> 00:10:19,470 Now, with that said, 187 00:10:19,470 --> 00:10:22,180 I will go back to this node application 188 00:10:22,180 --> 00:10:25,200 which will serve as an example for the next lectures, 189 00:10:25,200 --> 00:10:27,960 but I hope it's clear that you cannot just use node 190 00:10:27,960 --> 00:10:30,170 and not just use web servers 191 00:10:30,170 --> 00:10:33,650 and that you can interact with the container 192 00:10:33,650 --> 00:10:35,480 exactly as you need to, 193 00:10:35,480 --> 00:10:38,000 if you don't need interaction you don't have to, 194 00:10:38,000 --> 00:10:39,200 but if you do need it 195 00:10:39,200 --> 00:10:42,513 you can communicate just as shown in the lecture.