1 00:00:02,610 --> 00:00:04,940 Hello and welcome to this lecture in this lecture 2 00:00:04,950 --> 00:00:12,440 We will discuss about one solution based on CNI in particular WeaveWorks. The WeaveWorks 3 00:00:12,470 --> 00:00:15,790 WeaveWorks weave CNI plugin. In the previous practice test, 4 00:00:15,840 --> 00:00:17,630 We saw how it is configured. 5 00:00:17,820 --> 00:00:20,640 Now we will see more details about how it works. 6 00:00:20,640 --> 00:00:26,910 We will start where we left off in the POD Networking Concepts section. We had our own custom CNI script 7 00:00:27,000 --> 00:00:33,270 that we built and integrated into kubelet through CNI. In the previous lecture we saw how, instead 8 00:00:33,270 --> 00:00:39,750 of our custom script, we can integrate the weave plugin. Let us now see how the weave solution works, 9 00:00:39,870 --> 00:00:42,900 as it is important to understand at least one solution 10 00:00:42,900 --> 00:00:47,010 well. You should then be able to relate this to other solutions as well. 11 00:00:47,010 --> 00:00:52,860 So the networking solution we set up manually had a routing table which mapped what networks are on 12 00:00:52,860 --> 00:00:53,630 what hosts. 13 00:00:53,670 --> 00:00:59,490 So when a packet is sent from one pod to the other, it goes out to the network, to the router and finds 14 00:00:59,490 --> 00:01:01,950 its way to the node that hosts that pod. 15 00:01:01,950 --> 00:01:07,440 Now that works for a small environment and in a simple network. But in larger environments with 100s 16 00:01:07,440 --> 00:01:10,710 of nodes in a cluster and 100s of PODs on each node, 17 00:01:10,710 --> 00:01:12,320 This is not practical. 18 00:01:12,330 --> 00:01:17,490 The routing table may not support so many entries and that is where you need to get creative and look 19 00:01:17,490 --> 00:01:19,200 for other solutions. 20 00:01:19,200 --> 00:01:25,950 Think of the kubernetes cluster as our company. And the nodes as different office sites. With each site, 21 00:01:25,950 --> 00:01:30,280 We have different departments and within each department we have different offices. 22 00:01:30,300 --> 00:01:37,410 Someone is office-1 wants to send a packet to office-3 and hands it over to the office boy. All he 23 00:01:37,410 --> 00:01:43,290 knows is it needs to go to office 3 and he doesn’t care who or how it is transported. The office 24 00:01:43,290 --> 00:01:50,370 boy takes the package, gets in his car, looks up address of the target office in GPS, uses directions 25 00:01:50,370 --> 00:01:55,590 on the street and finds his way to the destination site. Delivers the package to Payroll department 26 00:01:55,650 --> 00:02:01,710 who in turn forwards the package to office 3. This works just fine for now. We soon expand 27 00:02:01,710 --> 00:02:07,860 regions and countries and this process no longer works it's hard for the office boy to keep track of 28 00:02:07,890 --> 00:02:13,890 so many routes to these large number of offices across different countries and of course he can’t drive 29 00:02:13,920 --> 00:02:20,460 to these offices by himself. That’s where we decide to outsource all mailing and shipping activities 30 00:02:20,460 --> 00:02:23,070 to a company who does it best. 31 00:02:23,070 --> 00:02:25,230 Once the shipping company is engaged. 32 00:02:25,230 --> 00:02:30,680 The first thing that they do is place their agents in each of our company's sites. 33 00:02:30,690 --> 00:02:35,910 These agents are responsible for managing all shipping activities between sites. 34 00:02:35,910 --> 00:02:41,760 They also keep talking to each other and are well connected so they all know about each other's sites. 35 00:02:41,760 --> 00:02:44,670 The departments in them and the offices in them. 36 00:02:44,760 --> 00:02:52,560 And so when a package is sent from say office 10 to office 3 the shipping agent in that site intercepts 37 00:02:52,560 --> 00:02:55,460 the package, and looks at the target office name, 38 00:02:55,470 --> 00:03:01,200 He knows exactly in which site and department that office is in through his little internal network 39 00:03:01,200 --> 00:03:03,060 with his peers on the other sites. 40 00:03:03,060 --> 00:03:08,880 He then places this package into his own new package with the destination address said to the target 41 00:03:08,880 --> 00:03:11,810 sites location and then sends the package through. 42 00:03:11,820 --> 00:03:17,660 Once the package arrives at the destination it is again intercepted by the agent on that site. 43 00:03:17,670 --> 00:03:24,180 He opens the packet retrieves the original packet and delivers it to the right department. Back to a 44 00:03:24,180 --> 00:03:28,170 world, when the weave CNI plugin is deployed on a cluster, 45 00:03:28,200 --> 00:03:34,470 it deploys an agent or service on each node. They communicate with each other to exchange information 46 00:03:34,470 --> 00:03:37,310 regarding the nodes and networks and PODs within them. 47 00:03:37,320 --> 00:03:41,960 Each agent or peer stores a topology of the entire setup, 48 00:03:42,030 --> 00:03:45,730 that way they know the pods and their IPs on the other nodes. 49 00:03:45,830 --> 00:03:49,490 Weave creates its own bridge on the nodes and names it 50 00:03:49,500 --> 00:03:56,670 weave. Then assigns IP address to each network. The Ips shown here are examples only. In the upcoming 51 00:03:56,670 --> 00:03:57,500 practice test. 52 00:03:57,510 --> 00:04:02,390 test you will figure out the exact range of IP addresses weave assigns on each node. 53 00:04:02,400 --> 00:04:07,740 We will talk about IPAM and how IP addresses are handed out to PODs and containers 54 00:04:07,860 --> 00:04:09,390 in the next lecture. 55 00:04:09,390 --> 00:04:13,500 Remember that a single POD may be attached to multiple bridge networks. 56 00:04:13,500 --> 00:04:18,480 For example you could have a pod attached to the weave bridge as well as the docker bridge created by 57 00:04:18,480 --> 00:04:18,890 Docker. 58 00:04:18,900 --> 00:04:24,900 What path a packet takes to reach destination depends on the route configured on the container. Weave 59 00:04:24,900 --> 00:04:30,840 makes sure that PODs get the correct route configured to reach the agent. And the agent then takes care 60 00:04:30,840 --> 00:04:32,350 of other PODs. 61 00:04:32,500 --> 00:04:39,420 now when a packet is sent from one pod to another on another node, weave intercepts the packet and identifies 62 00:04:39,420 --> 00:04:40,890 that it's on a separate network. 63 00:04:40,890 --> 00:04:46,440 It then encapsulates this packet into a new one with new source and destination and sends it across 64 00:04:46,470 --> 00:04:47,050 the network. 65 00:04:47,070 --> 00:04:53,310 Once on the other side, the other weave agent retrieves the packet, decapsulates and routes the packet 66 00:04:53,310 --> 00:04:55,090 to the right POD. 67 00:04:55,110 --> 00:04:58,470 So how do we deploy weave on a kubernetes cluster? 68 00:04:58,580 --> 00:05:05,450 Weave and weave peers can be deployed as services or daemons on each node in the cluster manually or 69 00:05:05,450 --> 00:05:07,210 if kubernetes is setup already 70 00:05:07,220 --> 00:05:11,700 Then an easier way to do that is to deploy it as pods in the cluster. 71 00:05:11,750 --> 00:05:16,880 Once the base kubernetes system is ready with nodes and networking configured correctly between the 72 00:05:16,880 --> 00:05:22,460 nodes and the basic control plan components are deployed, weave can be deployed in the cluster with a single 73 00:05:22,730 --> 00:05:24,470 kubectl apply command. 74 00:05:24,470 --> 00:05:28,730 This deploys all the necessary components required for weave in the cluster. 75 00:05:28,730 --> 00:05:35,090 Most importantly the weave peers are deployed as a daemonset. A daemonset ensures that one pod of 76 00:05:35,090 --> 00:05:38,420 the given kind is deployed on all nodes in the cluster. 77 00:05:38,420 --> 00:05:41,010 This works perfectly for the weave peers. 78 00:05:41,120 --> 00:05:47,210 If you deployed your cluster with the kubeadm tool and weave plugin, you can see the weave peers as pods 79 00:05:47,270 --> 00:05:50,530 deployed on each node. For troubleshooting purpose 80 00:05:50,690 --> 00:05:53,360 view the logs using the kubectl logs 81 00:05:53,360 --> 00:05:57,570 Command. Well that's it for this lecture. 82 00:05:57,570 --> 00:05:58,790 I will see you in the next.