1 00:00:02,050 --> 00:00:03,980 Sending HTTP requests 2 00:00:03,980 --> 00:00:06,250 to outside APIs works, 3 00:00:06,250 --> 00:00:07,790 but what about services 4 00:00:07,790 --> 00:00:11,110 or servers running on our local host machine? 5 00:00:11,110 --> 00:00:13,240 At the moment, this is not working, 6 00:00:13,240 --> 00:00:16,720 which is why I had to comment this code out. 7 00:00:16,720 --> 00:00:21,470 Now I will comment it back in and remove this line here. 8 00:00:21,470 --> 00:00:25,550 And now I wanna make sure that my Dockerize application 9 00:00:25,550 --> 00:00:30,510 is able to talk to my locally installed MongoDB database. 10 00:00:30,510 --> 00:00:33,270 Now, you will only be able to follow along 11 00:00:33,270 --> 00:00:35,200 if you installed MongoDB, 12 00:00:35,200 --> 00:00:37,440 as I showed you a couple of minutes ago. 13 00:00:37,440 --> 00:00:39,250 But you don't need to do that 14 00:00:39,250 --> 00:00:41,880 because this will only be an intermediate step 15 00:00:41,880 --> 00:00:45,970 until we later also put MongoDB into a container. 16 00:00:45,970 --> 00:00:48,520 But for the moment, it's not in a container. 17 00:00:48,520 --> 00:00:52,900 MongoDB is installed and running on my local machine. 18 00:00:52,900 --> 00:00:55,990 So not in a container, but on my local machine. 19 00:00:55,990 --> 00:00:59,290 This Node app on the other hand is in a container. 20 00:00:59,290 --> 00:01:01,930 And we just saw that this code here 21 00:01:01,930 --> 00:01:03,773 won't work just like that. 22 00:01:04,670 --> 00:01:06,400 So how can we make it work? 23 00:01:06,400 --> 00:01:10,020 For that all first stopped my running Node container 24 00:01:10,020 --> 00:01:12,730 so that we can restarted it later. 25 00:01:12,730 --> 00:01:15,340 But that alone, of course won't do the trick. 26 00:01:15,340 --> 00:01:17,220 Just restarting is not enough. 27 00:01:17,220 --> 00:01:19,930 We need to change something about this code 28 00:01:19,930 --> 00:01:22,793 or about the way we start this container. 29 00:01:23,870 --> 00:01:28,690 And for communication between your Dockerize application 30 00:01:28,690 --> 00:01:31,140 and your code in your Docker container 31 00:01:31,140 --> 00:01:33,320 and your local host machine 32 00:01:33,320 --> 00:01:35,400 for this kind of communication, 33 00:01:35,400 --> 00:01:39,530 you really only need to change your code in here. 34 00:01:39,530 --> 00:01:43,430 You don't need to start your container differently. 35 00:01:43,430 --> 00:01:46,570 Instead, there is a special instruction, 36 00:01:46,570 --> 00:01:50,750 a special hint you can give to Docker in your code. 37 00:01:50,750 --> 00:01:54,400 There is a special address you can use for your requests. 38 00:01:54,400 --> 00:01:58,980 You need to replace local hosts with a special domain, 39 00:01:58,980 --> 00:02:00,860 which is understood by Docker 40 00:02:00,860 --> 00:02:04,453 and that's host.docker.internal. 41 00:02:05,660 --> 00:02:08,840 This special domain is recognized by Docker. 42 00:02:08,840 --> 00:02:10,729 It's understood by Docker. 43 00:02:10,729 --> 00:02:15,730 And it's translated to the IP address off your host machine 44 00:02:15,940 --> 00:02:19,400 as seen from inside the Docker container. 45 00:02:19,400 --> 00:02:23,730 And you can use this anywhere where you need a domain, 46 00:02:23,730 --> 00:02:25,530 where you need a URL. 47 00:02:25,530 --> 00:02:28,660 Here, it's for a MongoDB type of request. 48 00:02:28,660 --> 00:02:31,410 But it could also be for an HTTP request, 49 00:02:31,410 --> 00:02:34,370 if you had some web server running on your machine 50 00:02:34,370 --> 00:02:36,810 and your code would need to talk to that. 51 00:02:36,810 --> 00:02:38,483 Here, it's MongoDB though. 52 00:02:39,400 --> 00:02:40,260 Now under the hood, 53 00:02:40,260 --> 00:02:43,620 this will be transformed to this IP address 54 00:02:43,620 --> 00:02:44,970 off your local host machine 55 00:02:44,970 --> 00:02:47,410 as seen from inside this container. 56 00:02:47,410 --> 00:02:48,380 But the great thing is 57 00:02:48,380 --> 00:02:50,350 that you don't have to worry about that. 58 00:02:50,350 --> 00:02:52,870 You just use this special domain 59 00:02:52,870 --> 00:02:55,740 and Docker will do the rest. 60 00:02:55,740 --> 00:02:57,140 So to make this work, 61 00:02:57,140 --> 00:03:00,340 we now need to rebuild this image 62 00:03:00,340 --> 00:03:03,090 since we changed the source code. 63 00:03:03,090 --> 00:03:05,730 And after this image was rebuilt, 64 00:03:05,730 --> 00:03:07,660 we can run our container again, 65 00:03:07,660 --> 00:03:10,563 based on this rebuild updated image. 66 00:03:11,470 --> 00:03:13,550 So I will hit enter here. 67 00:03:13,550 --> 00:03:16,540 And if we now inspect the running containers, 68 00:03:16,540 --> 00:03:19,493 we see that this container is up and running. 69 00:03:20,410 --> 00:03:22,950 And if I try this with Postman 70 00:03:22,950 --> 00:03:27,280 and I send a GET request to local host 3,000 favorites, 71 00:03:27,280 --> 00:03:28,770 I get this favorite, 72 00:03:28,770 --> 00:03:31,233 which I stored a couple of lectures ago. 73 00:03:32,090 --> 00:03:34,430 Because I'm now successfully talking 74 00:03:34,430 --> 00:03:38,640 to this MongoDB database which runs on my host machine, 75 00:03:38,640 --> 00:03:42,433 but I'm talking to it, from inside this Dockerize Node app. 76 00:03:43,510 --> 00:03:46,200 And the data which has stored a couple of lectures ago 77 00:03:46,200 --> 00:03:47,380 is still there, 78 00:03:47,380 --> 00:03:49,880 because this database is at the moment 79 00:03:49,880 --> 00:03:51,760 not running in a container, 80 00:03:51,760 --> 00:03:53,080 but on my host machine. 81 00:03:53,080 --> 00:03:56,060 And therefor all the data of course survives. 82 00:03:56,060 --> 00:03:59,500 And this therefor proofs that this communication 83 00:03:59,500 --> 00:04:02,810 from inside your Dockerize app to your host machine 84 00:04:02,810 --> 00:04:07,560 is also possible with this special domain. 85 00:04:07,560 --> 00:04:10,950 And that's the second type of communication, 86 00:04:10,950 --> 00:04:13,430 from Dockerize app to host machine. 87 00:04:13,430 --> 00:04:15,850 So from the container to host machine. 88 00:04:15,850 --> 00:04:20,850 This works but you need to use host.docker.internal 89 00:04:21,910 --> 00:04:25,560 as a URL, as a domain, so to say. 90 00:04:25,560 --> 00:04:29,180 Then Docker can do all required transformations 91 00:04:29,180 --> 00:04:32,233 and it's able to ensure that this communication 92 00:04:32,233 --> 00:04:35,113 between container and host machine works.