WEBVTT 00:01.050 --> 00:01.883 Instructor: In the last section, 00:01.883 --> 00:04.260 we started talking about the overall architecture of the app 00:04.260 --> 00:05.760 that we're going to put together. 00:05.760 --> 00:07.200 Again, I can't say it enough, 00:07.200 --> 00:08.880 way more complicated than it needs to be, 00:08.880 --> 00:11.490 just so we have multiple containers to work with. 00:11.490 --> 00:12.323 So in this section, 00:12.323 --> 00:14.010 we're gonna start putting together the source code 00:14.010 --> 00:15.960 for the entire application. 00:15.960 --> 00:18.240 A quick note here in this section 00:18.240 --> 00:19.770 and the next couple of videos, 00:19.770 --> 00:21.480 we're going to be putting together 00:21.480 --> 00:24.180 the JavaScript side of the application. 00:24.180 --> 00:26.670 We're not gonna touch any Docker stuff for right now. 00:26.670 --> 00:29.190 So no Dockerfiles, no Docker Compose, 00:29.190 --> 00:30.630 no Travis, no deployment, 00:30.630 --> 00:32.100 nothing like that. 00:32.100 --> 00:33.600 The reason that we're gonna focus just 00:33.600 --> 00:35.190 on the JavaScript side for right now, 00:35.190 --> 00:39.060 is that if you do not care about all this JavaScript stuff 00:39.060 --> 00:40.530 like you don't care about React, 00:40.530 --> 00:41.850 you don't care about Express, 00:41.850 --> 00:43.320 you don't care about any of that stuff, 00:43.320 --> 00:44.940 totally fine. 00:44.940 --> 00:46.230 You can skip this video 00:46.230 --> 00:47.340 and the next couple, 00:47.340 --> 00:49.050 you can move on to the next section. 00:49.050 --> 00:50.130 And in that section, 00:50.130 --> 00:51.690 I'm gonna post all the code 00:51.690 --> 00:54.120 that we're gonna write right now up for download. 00:54.120 --> 00:56.220 So if you don't care about JavaScript stuff at all, 00:56.220 --> 00:57.053 totally fine. 00:57.053 --> 00:57.990 Pause the video here, 00:57.990 --> 01:00.060 and skip ahead a couple of videos. 01:00.060 --> 01:02.520 I wanna make sure that if you are not a JavaScript person, 01:02.520 --> 01:04.590 you don't have to sit through all this stuff. 01:04.590 --> 01:05.880 I'm only showing how to put 01:05.880 --> 01:07.290 the application together from scratch 01:07.290 --> 01:09.570 in case you are a JavaScript person 01:09.570 --> 01:12.120 and you're kinda curious about how to work with Redis 01:12.120 --> 01:13.440 and set up this kind of like, 01:13.440 --> 01:14.820 worker over here, 01:14.820 --> 01:16.470 and Postgres and Redis, 01:16.470 --> 01:18.210 and all that kind of other good stuff. 01:18.210 --> 01:20.760 So again, if you don't care about the JavaScript stuff, 01:20.760 --> 01:23.280 pause here, skip forward a couple videos. 01:23.280 --> 01:26.253 Otherwise, we're gonna get started right now. 01:27.420 --> 01:29.220 Okay, so the first thing we're gonna put together 01:29.220 --> 01:31.500 is this worker process. 01:31.500 --> 01:34.020 Remember, the worker process is going to watch Redis 01:34.020 --> 01:37.140 for any new indexes that get inserted. 01:37.140 --> 01:41.070 Anytime the worker sees a new index added to Redis 01:41.070 --> 01:42.480 it's gonna pull that index 01:42.480 --> 01:45.900 and then calculate the appropriate Fibonacci value for it. 01:45.900 --> 01:47.580 Now, as we put this worker together, 01:47.580 --> 01:49.590 I'm not gonna tell you too much about 01:49.590 --> 01:51.150 the behind the scenes stuff, 01:51.150 --> 01:53.280 like specifically how we work with Redis 01:53.280 --> 01:54.540 from JavaScript code, 01:54.540 --> 01:56.760 because that's not really the goal of this course. 01:56.760 --> 01:58.770 But I will give you just a little bit of commentary 01:58.770 --> 02:01.710 to make sure you have the general idea of what's going on. 02:01.710 --> 02:02.763 So let's get to it. 02:03.750 --> 02:07.260 I'm gonna first begin by changing on over to my terminal. 02:07.260 --> 02:08.190 You'll notice that I'm back 02:08.190 --> 02:10.140 in a workspace directory of sorts, 02:10.140 --> 02:12.420 so I'm no longer inside of any of the folders 02:12.420 --> 02:14.430 that we've been working on so far. 02:14.430 --> 02:15.840 I'm gonna make a new folder inside 02:15.840 --> 02:18.510 of here called, "Complex." 02:18.510 --> 02:19.530 And the idea behind this 02:19.530 --> 02:20.970 is that the name of our application 02:20.970 --> 02:23.703 will be kind of like a more complex application. 02:24.930 --> 02:27.510 I'm then going to change into that folder 02:27.510 --> 02:28.343 and then inside of here 02:28.343 --> 02:29.670 I'm gonna make another folder 02:29.670 --> 02:31.650 that's gonna house all of the source code 02:31.650 --> 02:33.930 for this kind of worker process 02:33.930 --> 02:37.110 that's gonna calculate the actual Fibonacci values. 02:37.110 --> 02:40.830 So I'll make a new folder inside of here called, "Worker." 02:40.830 --> 02:41.663 And then finally, 02:41.663 --> 02:43.380 I'm gonna start up my code editor inside 02:43.380 --> 02:45.483 of the complex directory. 02:48.540 --> 02:49.413 All right. 02:50.610 --> 02:53.250 So here's the worker folder that we just created. 02:53.250 --> 02:54.780 I'm gonna first begin by adding 02:54.780 --> 02:57.930 a package.json file to it. 02:57.930 --> 02:59.820 So inside the worker directory, 02:59.820 --> 03:02.133 I'll make a package.json file. 03:03.330 --> 03:04.470 Then inside of here, 03:04.470 --> 03:07.380 we'll put down a little bit of configuration. 03:07.380 --> 03:09.840 We're gonna add in a couple of dependencies 03:09.840 --> 03:11.640 that we're going to need. 03:11.640 --> 03:15.120 The first dependency that I'm going to want is nodemon, 03:15.120 --> 03:18.180 which is gonna give us some live reload of code anytime 03:18.180 --> 03:21.330 that we change the source of our project. 03:21.330 --> 03:23.790 We'll go more into that a little bit later. 03:23.790 --> 03:28.203 The version of nodemon that I'm gonna get is 1.18.3. 03:29.460 --> 03:31.350 I'm also gonna get a Redis client 03:31.350 --> 03:33.930 that will allow us to connect to a copy of Redis 03:33.930 --> 03:35.370 and pull values out of it 03:35.370 --> 03:38.010 and do all the stuff that we need to do with Redis. 03:38.010 --> 03:42.453 And for that, I'm gonna get version 2.8.0, like so. 03:44.070 --> 03:44.903 Now, at this point, 03:44.903 --> 03:46.650 please make sure that you're keeping track 03:46.650 --> 03:48.690 of the code that I'm typing 03:48.690 --> 03:49.740 and the code you're typing. 03:49.740 --> 03:51.840 Please double-check for typos and whatnot 03:51.840 --> 03:53.850 because we're not gonna run any of this code 03:53.850 --> 03:55.260 for several sections. 03:55.260 --> 03:56.760 So if you make a typo in here, 03:56.760 --> 03:58.890 it's gonna be kinda challenging to come back later on 03:58.890 --> 04:01.140 and find where you made that typo. 04:01.140 --> 04:03.210 So for example, make sure you get the comma 04:03.210 --> 04:04.890 at the end of the nodemon line, 04:04.890 --> 04:06.420 make sure you do not have a comma 04:06.420 --> 04:07.770 at the end of the Redis sign, 04:07.770 --> 04:08.603 and so on. 04:09.750 --> 04:12.030 So now we're going to also put a script section 04:12.030 --> 04:13.200 in here as well. 04:13.200 --> 04:16.590 I'm gonna add a comma at the end of dependencies, 04:16.590 --> 04:18.093 and I'll put in scripts. 04:18.990 --> 04:21.210 And then we're gonna add on a start script 04:21.210 --> 04:23.970 of node index.js, 04:23.970 --> 04:26.820 and I'll do a dev script of simply, 04:26.820 --> 04:28.203 nodemon, like so. 04:30.300 --> 04:32.640 All right, so that's it for our package.json file. 04:32.640 --> 04:36.450 Again, please double-check the placement of your commas. 04:36.450 --> 04:37.283 Please make sure 04:37.283 --> 04:39.480 that you're using double quotes everywhere inside of here, 04:39.480 --> 04:40.890 and both all the keys 04:40.890 --> 04:42.900 and all the values should have double quotes 04:42.900 --> 04:43.953 around them as well. 04:45.330 --> 04:47.460 So that's all we need for package.json. 04:47.460 --> 04:49.440 I'm now gonna create a separate file inside 04:49.440 --> 04:52.560 of here called, "index.js." 04:52.560 --> 04:55.020 So this is where we're gonna put all of our primary logic 04:55.020 --> 04:56.880 for connecting to Redis, 04:56.880 --> 04:57.990 watching for values, 04:57.990 --> 05:00.993 and then eventually, calculating our Fibonacci value. 05:02.850 --> 05:05.700 All the configuration or kind of keys 05:05.700 --> 05:08.250 that we're going to need for connecting over to Redis 05:08.250 --> 05:10.710 are gonna be stored inside of a separate file. 05:10.710 --> 05:12.690 So the first thing I'm gonna do inside of here 05:12.690 --> 05:17.310 is require in a file that we're going to call, "Keys." 05:17.310 --> 05:19.890 And again, this file is gonna house the host name 05:19.890 --> 05:23.013 and the port required for connecting over to Redis. 05:24.360 --> 05:25.860 So inside of the worker folder, 05:25.860 --> 05:30.177 I'm gonna make another file called, "Keys.js," 05:31.140 --> 05:32.130 and inside of here, 05:32.130 --> 05:34.713 we're gonna add in a module.exports. 05:36.000 --> 05:37.680 That's gonna be an object, 05:37.680 --> 05:42.680 that's gonna have a Redis host of process.env Redis host, 05:44.160 --> 05:49.160 and a Redis port of process.env Redis port. 05:52.860 --> 05:54.810 So anytime that we want to connect to Redis, 05:54.810 --> 05:56.820 we're gonna look for the host name 05:56.820 --> 06:00.000 or essentially, URL of sorts, for Redis, 06:00.000 --> 06:02.670 and the port that we're supposed to connect to it from, 06:02.670 --> 06:04.710 from our environment variables. 06:04.710 --> 06:06.300 So when we run this application, 06:06.300 --> 06:08.370 we darn sure better well have 06:08.370 --> 06:10.380 a Redis host environment variable 06:10.380 --> 06:14.040 and a Redis port environment variable defined as well. 06:14.040 --> 06:16.410 So that's all we have to put inside the keys file. 06:16.410 --> 06:19.680 I'm gonna go back over to index.js 06:19.680 --> 06:20.513 and then inside of here, 06:20.513 --> 06:22.290 now that we've got our API keys, 06:22.290 --> 06:23.850 or essentially, just connection keys, 06:23.850 --> 06:25.290 I should call it, put together. 06:25.290 --> 06:26.970 We're gonna start putting together the logic 06:26.970 --> 06:30.603 to get a connection over to our Redis server. 06:31.560 --> 06:33.783 So I'm gonna first import a Redis client, 06:35.880 --> 06:37.530 we'll then create a Redis client. 06:42.900 --> 06:43.733 And to this thing, 06:43.733 --> 06:45.180 we're gonna pass an object 06:45.180 --> 06:49.350 that has a host of keys.redis host, 06:49.350 --> 06:52.110 a port of keys.redis port, 06:52.110 --> 06:54.150 and we're gonna add on one other little option 06:54.150 --> 06:59.150 in here called, "Retry underscore strategy." 06:59.340 --> 07:01.530 And this is gonna tell the Redis client 07:01.530 --> 07:02.700 that we're using right here, 07:02.700 --> 07:05.370 that if it ever loses connection to our Redis server, 07:05.370 --> 07:07.710 it should attempt to automatically reconnect 07:07.710 --> 07:10.470 to the server once every one second 07:10.470 --> 07:12.723 or once every 1,000 milliseconds. 07:14.700 --> 07:16.650 After that, we're going to make a duplicate 07:16.650 --> 07:18.600 of the Redis client that we just put together. 07:18.600 --> 07:20.940 We'll talk about why we're doing that in just a moment. 07:20.940 --> 07:25.940 We'll say, consSub is redisclient.duplicate, like so. 07:30.660 --> 07:32.250 All right, after that, 07:32.250 --> 07:33.840 we'll then put together the function 07:33.840 --> 07:35.190 that's going to be actually used 07:35.190 --> 07:37.860 for calculating these Fibonacci values, 07:37.860 --> 07:40.020 given some particular index. 07:40.020 --> 07:42.240 So the work function, 07:42.240 --> 07:46.263 we'll say, function fib will be called with some index. 07:47.580 --> 07:50.970 We're gonna say, "If index is ever less than two, 07:50.970 --> 07:53.250 then we're going to return the value one, 07:53.250 --> 07:58.170 otherwise, we're going to return fib index minus one 07:58.170 --> 08:01.083 plus fib index minus two. 08:02.070 --> 08:04.020 This right here is a very classic solution 08:04.020 --> 08:06.273 to the Fibonacci sequence. 08:07.200 --> 08:09.960 It's going to return the value one 08:09.960 --> 08:12.930 if the index submitted is ever less than two. 08:12.930 --> 08:15.450 Otherwise, it's gonna take the previous two values 08:15.450 --> 08:17.670 add them together, and then return that. 08:17.670 --> 08:18.690 Now, we could talk for days 08:18.690 --> 08:20.820 about exactly how this solution right here works. 08:20.820 --> 08:22.950 If you want to, you could always go look at a blog post 08:22.950 --> 08:24.780 or two to get a better idea about 08:24.780 --> 08:27.420 the Fibonacci recursive solution. 08:27.420 --> 08:28.890 Now, we're very purposefully using 08:28.890 --> 08:30.780 a recursive solution right here 08:30.780 --> 08:32.100 because it's very slow 08:32.100 --> 08:34.050 and it's gonna give us kind of a better reason 08:34.050 --> 08:35.460 for making use of Redis 08:35.460 --> 08:37.650 and having a separate worker process 08:37.650 --> 08:40.050 to calculate these Fibonacci values. 08:40.050 --> 08:42.120 So this is not an ideal solution right here, 08:42.120 --> 08:45.180 but it's one that kinda simulates why we would want to have 08:45.180 --> 08:46.833 a separate worker process. 08:47.670 --> 08:49.620 Now, the last thing that we need to do inside of here, 08:49.620 --> 08:51.990 we're going to use the Redis client connection 08:51.990 --> 08:53.040 we just put together. 08:53.040 --> 08:54.120 We're gonna watch Redis 08:54.120 --> 08:56.820 for any time we get a new value inserted into it. 08:56.820 --> 08:58.500 And anytime we see a new value, 08:58.500 --> 09:01.450 we're gonna run our fib function that we just put together. 09:02.460 --> 09:03.720 We'll say, oops, 09:03.720 --> 09:04.770 we'll say, sub, 09:04.770 --> 09:06.870 which remember, is the duplicate client right here. 09:06.870 --> 09:08.790 Sub stands for subscription 09:08.790 --> 09:10.020 'cause we're gonna watch Redis, 09:10.020 --> 09:13.530 and get a message anytime that a new value shows up. 09:13.530 --> 09:15.903 We'll say, sub.on message. 09:16.740 --> 09:19.890 So anytime that we get a new message, 09:19.890 --> 09:21.570 run this callback function 09:21.570 --> 09:23.170 that we're gonna add right here. 09:24.600 --> 09:26.160 The callback function will be called 09:26.160 --> 09:28.980 with something called a channel 09:28.980 --> 09:29.973 and a message. 09:32.520 --> 09:35.410 We'll then say, redisclient.hsetvalues message. 09:40.080 --> 09:40.913 And then finally, 09:40.913 --> 09:43.110 we're gonna calculate the actual Fibonacci value 09:43.110 --> 09:46.920 by saying fib, parseInt, 09:46.920 --> 09:48.750 and message, like so. 09:48.750 --> 09:51.143 And let me zoom out so you can see that whole line. 09:52.890 --> 09:56.850 So anytime that we get a new value that shows up in Redis, 09:56.850 --> 10:00.120 we're going to calculate a new Fibonacci value 10:00.120 --> 10:03.780 and then insert that into a hash of values 10:03.780 --> 10:05.820 or a hash called, "Values." 10:05.820 --> 10:07.950 The key will be the index that we receive. 10:07.950 --> 10:10.140 So message right here is going to be the index value 10:10.140 --> 10:11.940 that was submitted into our form 10:11.940 --> 10:14.520 and then we push in the value for Fibonacci sequence 10:14.520 --> 10:17.010 that we just calculated as well. 10:17.010 --> 10:17.843 And then the last thing 10:17.843 --> 10:19.290 that we're gonna do inside this file, 10:19.290 --> 10:21.040 we'll say, sub.subscribe 10:23.010 --> 10:25.440 to any insert event. 10:25.440 --> 10:28.920 So anytime someone inserts a new value into Redis, 10:28.920 --> 10:30.540 we're gonna get that value, 10:30.540 --> 10:33.120 and attempt to calculate the Fibonacci value for it, 10:33.120 --> 10:37.260 and then toss that value back into the Redis instance. 10:37.260 --> 10:38.130 All right, so like I said, 10:38.130 --> 10:40.140 we're going very light on detail right now, 10:40.140 --> 10:43.050 because this is super off topic related to 10:43.050 --> 10:45.330 or compared to the actual Docker stuff 10:45.330 --> 10:46.950 that we're trying to talk about. 10:46.950 --> 10:48.060 The very last thing I want to do 10:48.060 --> 10:51.510 is I wanna try to run this index.js file. 10:51.510 --> 10:53.460 The file's not gonna run successfully, 10:53.460 --> 10:54.840 but it should at least tell us whether 10:54.840 --> 10:57.000 or not you have a typo in here. 10:57.000 --> 10:58.560 So back at my terminal, 10:58.560 --> 11:02.460 I'm gonna change into that worker directory. 11:02.460 --> 11:03.480 And then inside of here, 11:03.480 --> 11:07.830 I'm gonna execute nodeindex.js. 11:07.830 --> 11:09.607 Now if you see a message right here that says, 11:09.607 --> 11:12.120 "Cannot find module Redis," that's good. 11:12.120 --> 11:13.560 That's what we want to see. 11:13.560 --> 11:15.180 If you made a typo somewhere in here, 11:15.180 --> 11:17.760 like let's say, I have an extra colon or three 11:17.760 --> 11:19.203 on this line right here, 11:20.280 --> 11:22.200 and then I try to run nodeindex.js, 11:22.200 --> 11:23.460 I'll see a different message. 11:23.460 --> 11:24.457 I'll see something that says, 11:24.457 --> 11:26.070 "Hey, you made a typo." 11:26.070 --> 11:29.730 So if you see anything other than "Cannot find module Redis" 11:29.730 --> 11:31.530 that means that you made a typo somewhere 11:31.530 --> 11:33.120 and you need to double-check 11:33.120 --> 11:36.600 and find that typo in your code and fix it. 11:36.600 --> 11:38.400 All right, so that's it for the worker process. 11:38.400 --> 11:39.570 Let's take a quick pause right here 11:39.570 --> 11:41.520 and we'll continue in the next section.