WEBVTT 00:00.240 --> 00:02.730 -: We've now finished up our first little application 00:02.730 --> 00:03.563 using Docker. 00:03.563 --> 00:05.580 We're now gonna start working on our second application, 00:05.580 --> 00:08.430 which is gonna be a little bit more complicated in nature 00:08.430 --> 00:09.780 and it's going to require us to learn 00:09.780 --> 00:11.880 some more advanced features around Docker. 00:11.880 --> 00:13.560 Let's first take a look at a mock-up 00:13.560 --> 00:15.010 of what we're going to build. 00:16.050 --> 00:17.190 All right, so here it is. 00:17.190 --> 00:20.580 This is really a classic example of Docker in action. 00:20.580 --> 00:22.680 You're gonna find a lot of other applications out there 00:22.680 --> 00:24.540 that are very similar in nature. 00:24.540 --> 00:26.370 So the purpose of this tiny little application 00:26.370 --> 00:28.560 is to make a Docker container that contains 00:28.560 --> 00:32.310 a web application that simply displays inside the browser 00:32.310 --> 00:34.920 the number of times that someone essentially 00:34.920 --> 00:36.540 has visited this server. 00:36.540 --> 00:38.167 And so you can see right now it says, 00:38.167 --> 00:40.560 "Number of visits, 10," that indicates that this page 00:40.560 --> 00:43.140 has been visited 10 times. 00:43.140 --> 00:44.370 Now, in order to build this, 00:44.370 --> 00:46.713 we're gonna need two separate components. 00:48.120 --> 00:50.430 First off, we're gonna need some type of web server, 00:50.430 --> 00:53.280 something to actually respond to HTTP requests 00:53.280 --> 00:56.310 and generate some HTML to show inside the browser. 00:56.310 --> 00:58.350 To actually store the number of times 00:58.350 --> 00:59.850 that this thing has been visited, 00:59.850 --> 01:03.390 we're going to also make use of a little Redis server. 01:03.390 --> 01:05.700 Remember, Redis is an in-memory data store. 01:05.700 --> 01:08.850 You can essentially think of it as a tiny little database 01:08.850 --> 01:10.650 that sits entirely inside of memory. 01:11.610 --> 01:13.770 The only purpose of the Redis server is going to be 01:13.770 --> 01:15.540 to contain the number of times 01:15.540 --> 01:17.340 that the page has been visited. 01:17.340 --> 01:19.020 Now, something to be aware of here, 01:19.020 --> 01:21.750 yes, we absolutely could store this number of visits 01:21.750 --> 01:23.820 inside the Node application itself. 01:23.820 --> 01:25.230 That's totally an option. 01:25.230 --> 01:26.880 However, just to make this thing a little bit more, 01:26.880 --> 01:28.500 kind of, sufficiently complicated, 01:28.500 --> 01:30.450 we are going to be making use of Redis. 01:31.410 --> 01:32.460 Now, I wanna think a little bit 01:32.460 --> 01:34.320 about how we're going to generally architecture 01:34.320 --> 01:35.763 this app using Docker. 01:37.350 --> 01:40.050 And your first impression here, maybe your first guess, 01:40.050 --> 01:42.570 might be that we're going to make a single container 01:42.570 --> 01:44.190 and inside that single container 01:44.190 --> 01:48.150 we could run both our Node application and a Redis server. 01:48.150 --> 01:50.730 Now, don't get me wrong, this is totally possible, 01:50.730 --> 01:53.040 you could take this approach right here. 01:53.040 --> 01:56.460 However, if this application ever got popular to any degree, 01:56.460 --> 01:58.380 it would start to have some issues. 01:58.380 --> 02:00.810 Let tell you what the issue would be. 02:00.810 --> 02:02.940 Let's imagine that you start getting a lot of traffic 02:02.940 --> 02:05.460 to this little, somewhat useless website 02:05.460 --> 02:06.840 that you've put together. 02:06.840 --> 02:08.430 As you start to get more and more traffic, 02:08.430 --> 02:10.290 you're probably going to want to introduce 02:10.290 --> 02:13.080 more web application servers 02:13.080 --> 02:16.020 to respond to incoming HTTP requests, 02:16.020 --> 02:18.090 and so in order to make additional servers, 02:18.090 --> 02:19.980 you might create additional instances 02:19.980 --> 02:21.180 of your Docker container 02:21.180 --> 02:23.430 that contains both the Node application 02:23.430 --> 02:25.860 and an instance of Redis. 02:25.860 --> 02:27.240 The issue with this approach 02:27.240 --> 02:30.090 is that every one of these different Redis servers 02:30.090 --> 02:33.630 would be completely disconnected from each other. 02:33.630 --> 02:36.450 And so one server, one Redis instance over here 02:36.450 --> 02:38.220 inside this Docker container, 02:38.220 --> 02:41.910 might think that the page has been visited 99 times, 02:41.910 --> 02:44.940 but then some other Redis instance in another container 02:44.940 --> 02:48.270 might think that it's only been visited three times. 02:48.270 --> 02:50.520 So in general, we would definitely not want 02:50.520 --> 02:53.310 to create multiple instances of a Redis instance 02:53.310 --> 02:54.660 for a single app. 02:54.660 --> 02:57.300 Instead, we would want to have one single instance, 02:57.300 --> 03:00.030 and then if we need to scale up the web application itself, 03:00.030 --> 03:01.920 we could just scale the Node server 03:01.920 --> 03:05.250 and make additional instances of the Node server. 03:05.250 --> 03:06.660 So essentially what we're going to do 03:06.660 --> 03:07.500 is gonna be something that looks 03:07.500 --> 03:09.510 a little bit more like this. 03:09.510 --> 03:12.330 We are gonna have separate Docker containers 03:12.330 --> 03:15.870 for both the Node application and the Redis server. 03:15.870 --> 03:18.450 Each of the Docker containers that holds the Node app 03:18.450 --> 03:21.840 will connect somehow over to the Redis instance 03:21.840 --> 03:23.430 in this separate container, 03:23.430 --> 03:27.960 and store the current count or current visit variable 03:27.960 --> 03:29.883 inside of that Redis server instead. 03:31.080 --> 03:33.120 Now, for the first iteration of this project, 03:33.120 --> 03:35.370 we're not gonna worry about scaling just yet, 03:35.370 --> 03:37.290 so we're really going to be setting up something 03:37.290 --> 03:40.290 that looks like this right here. 03:40.290 --> 03:43.350 We've got one Docker container that contains our Node app 03:43.350 --> 03:45.060 and then a second container that has just 03:45.060 --> 03:47.040 the Redis server inside of it. 03:47.040 --> 03:49.560 So, with that in mind, let's take a quick break right here. 03:49.560 --> 03:50.790 We're gonna come back the next section 03:50.790 --> 03:52.530 and we're gonna start writing out the code 03:52.530 --> 03:54.330 for our Node application. 03:54.330 --> 03:56.633 So quick break, and I'll see you in just a minute.