WEBVTT 00:00.860 --> 00:03.320 Hello and welcome to this lecture in this lecture 00:03.320 --> 00:11.030 we will discuss about the Kubernetes Service -ClusterIP. A full stack web application typically has 00:11.060 --> 00:15.420 different kinds of pods hosting different parts of an application. 00:15.590 --> 00:22.040 You may have a number of pods running a front end web server another set of pods running a back end 00:22.040 --> 00:29.480 server, a set of PODs running a key-value store like Redis, another set of PODs running a persistent 00:29.480 --> 00:36.990 database like MySQL. The web front end server needs to communicate to the back end servers and 00:36.990 --> 00:42.420 and the backend-workers need to connect to database as well as the redis services etc.. 00:42.690 --> 00:51.180 So what is the right way to establish connectivity between these services or tiers of my application. 00:51.390 --> 00:58.440 The pods all have an IP address assigned to them as we can see on the screen but these IP as we 00:58.440 --> 01:00.360 know are not static. 01:00.360 --> 01:05.580 These pods can go down any time and new pods are created all the time. 01:05.580 --> 01:12.060 And so you cannot rely on these IP addresses for internal communication between the application. 01:12.060 --> 01:21.130 Also what if the first front-end POD at 10.244.0.3 need to connect to a backend service? 01:21.330 --> 01:23.240 Which of the three would it go to 01:23.280 --> 01:25.430 and who makes that decision. 01:25.650 --> 01:33.540 A kubernetes service can help us group these PODs together and provide a single interface to access 01:33.540 --> 01:35.730 the PODs in a group. 01:35.850 --> 01:43.320 For example a service created for the backend PODs will help group all the backend PODs together and 01:43.320 --> 01:48.490 provide a single interface for other PODs to access this service. 01:48.750 --> 01:54.140 The requests are forwarded to one of the PODs under the service randomly. 01:54.210 --> 02:00.660 Similarly create additional services for Redis and allow the backend parts to access the redis systems 02:00.660 --> 02:02.250 through the service. 02:02.250 --> 02:10.830 This enables us to easily and effectively deploy a microservices based application on kubernetes cluster. 02:10.830 --> 02:18.810 Each layer can now scale or move as required without impacting communication between the various services. 02:18.900 --> 02:26.280 Each service gets an IP name assigned to it inside the cluster and that is the name that should be used 02:26.610 --> 02:29.680 by other pods to access the service. 02:29.700 --> 02:37.710 This type of service is known as cluster IP to create such a service as always use a definition file 02:38.040 --> 02:43.560 in the service definition file first used to default template which has API version kind. 02:43.560 --> 02:51.380 Metadata and spec the API version is V1 kind is a service and we will give a name to our service. 02:51.420 --> 03:00.240 We will call it backend under specification we have type and ports the type is cluster IP in fact cluster 03:00.240 --> 03:02.370 IP is the default type. 03:02.370 --> 03:10.430 So even if you didn't specify it it will automatically assume the type to be cluster IP under ports. 03:10.440 --> 03:18.370 We have a target port and port the target port is the port where the backend is exposed which in this 03:18.370 --> 03:24.830 case is 80 and the port is where the service is exposed which is 80 as well. 03:25.180 --> 03:33.040 To link the service to a set of pods we use selector we will refer to the pod definition file and 03:33.040 --> 03:38.530 copy the labels from it and remove it under selector and that should be it. 03:38.650 --> 03:45.580 We can now create the service using the kubectl create command and then check its status using the 03:45.580 --> 03:48.630 kubectlget services command. 03:48.640 --> 03:57.080 The service can be accessed by other PODs using the ClusterIP or the service name. 03:57.160 --> 04:00.640 That's it for this lecture and I will see you in the next lecture.