1 00:00:02,370 --> 00:00:05,760 So in this session we are going to talk about Redis Replication. 2 00:00:08,920 --> 00:00:13,270 So whenever we are setting Redis Replication. 3 00:00:13,270 --> 00:00:18,290 Basically what we are doing is, we are setting a Master and aSlave instances. 4 00:00:18,580 --> 00:00:24,520 So you'll be having Redis Master running on, one of the servers and then you can have N number 5 00:00:24,520 --> 00:00:27,970 of Slaves running on different servers. 6 00:00:28,730 --> 00:00:29,070 Okay. 7 00:00:29,080 --> 00:00:36,760 So the scenario which we are going to see today. In this scenario we are going to create 3 Slaves instances 8 00:00:38,060 --> 00:00:44,570 Okay and then all of these 3, these 3 instances are going to be a replica of Master. 9 00:00:45,080 --> 00:00:50,480 So when I say Replica of Master, which means whatever key changes which are being done in Master that 10 00:00:50,480 --> 00:00:59,340 is automatically going to be synced in each of these Replicas and Master remains as usual. whenever you 11 00:00:59,340 --> 00:01:06,480 are setting Replication there is no difference in the Configuration of Master. However, in the Slave 12 00:01:06,570 --> 00:01:15,240 you need to go and edit Redis.conf file and in the Redis.conf file, you need to provide Master 13 00:01:15,270 --> 00:01:17,610 you know Master Redis Information. 14 00:01:17,610 --> 00:01:25,140 So we'll see how to provide those information and also major point to remember is, that all these read 15 00:01:25,140 --> 00:01:29,550 only, I mean all these Redis slave instances remains Read Only Mode. 16 00:01:30,330 --> 00:01:37,090 So all the users can connect to all the Slave Nodes but they can only do a Read Only Operations. 17 00:01:37,200 --> 00:01:45,500 So if, if any of the user tries to write any or tries to make any Key Changes in Redis Slave Instances, 18 00:01:45,540 --> 00:01:54,380 they are going to get the error that these instances are read only instance. However, if any user is connected 19 00:01:54,380 --> 00:02:03,770 to Master, they'll be able to perform Read and Write both the operations as usual. 20 00:02:03,780 --> 00:02:10,700 So now in our environment, we are going to run 4 instances of Redis on the same server. 21 00:02:11,230 --> 00:02:11,660 OK. 22 00:02:11,680 --> 00:02:17,430 But in a typical Production Environment, you are going to actually run all the Slaves on a Separate 23 00:02:17,430 --> 00:02:22,560 Server and also the Master is going to be on a Separate Server. 24 00:02:22,560 --> 00:02:28,830 However, for the purpose of demonstration we are just going to create 4 copies of this Redis Software 25 00:02:29,340 --> 00:02:34,290 and then we are going to make a change in the Port and then we'll be running all the 4 instances 26 00:02:34,290 --> 00:02:43,500 on the same server and we'll be making Configuration Change in each of the Slave Instance. 27 00:02:43,710 --> 00:02:45,060 So let's see how this works. 28 00:02:55,800 --> 00:03:00,930 So this is the current folder structure which we have. So right now I am in Redis admin's home directory 29 00:03:01,890 --> 00:03:08,500 and the software working Redis software, which we have installed previously, that was under Redis-stable 30 00:03:08,520 --> 00:03:09,800 directory. 31 00:03:09,840 --> 00:03:13,740 Now I am going to create exact copy of this software 32 00:03:17,780 --> 00:03:23,960 and to the master instance I'm going to name Redis-M 33 00:03:26,810 --> 00:03:33,340 and then all this slave instance from 1 to 3, I am going to name Redis-S1, Second instance 34 00:03:33,360 --> 00:03:39,240 is going to be called Redis-S 2 and third instance going to be called Redis-S 3 35 00:03:42,540 --> 00:03:51,480 OK now if you see this is our folder structure. So Master is here and then we have 3 Slaves. 36 00:03:51,500 --> 00:04:01,180 So now the Master can be started as usual and we need to make changes in the Configuration File of Slaves 37 00:04:01,190 --> 00:04:01,970 Redis Instance. 38 00:04:05,970 --> 00:04:13,830 Let's go to Master Directory first and Let's see if we would like to make any changes in the Configuration File 39 00:04:21,610 --> 00:04:25,470 Please notice that master is going to run on Port 6 3 7 0 40 00:04:28,790 --> 00:04:34,880 So this also means that we'll not be able to run all the other instances on this port. okay Master 41 00:04:34,880 --> 00:04:42,170 is going to use Port 6 3 7 0, then we will have to change the port for Slave 1 and make it some other port 42 00:04:42,320 --> 00:04:50,210 probably we can change it to 6 3 7 1 and Slave 2 we can change it to 6 3 7 2 and Slave 3 we will be changing it to 43 00:04:50,210 --> 00:04:51,590 6 3 7 3 44 00:05:02,900 --> 00:05:07,790 So other than this if you notice there is one more property which is called log file. So by default when 45 00:05:07,790 --> 00:05:17,310 we start this Redis instance, it is going to write all the logs in to /tmp/redis.log 46 00:05:17,330 --> 00:05:27,230 So I'm going to rename it to, Redis _m.log. So we'll be able to know the logs which is 47 00:05:27,230 --> 00:05:29,930 created by Redis Master Instance 48 00:05:37,540 --> 00:05:46,580 Okay here is our RDB File names. So this also I am going to change it to _m Postfix. So 49 00:05:46,580 --> 00:05:52,530 this is going to denote that this is a Master Node and then directory, I'm going to change it to 50 00:05:59,230 --> 00:06:08,020 let's keep/home/redisadmin. Okay so that's all. We can now close this one and we will not 51 00:06:08,020 --> 00:06:09,370 start Redis as of now. 52 00:06:09,370 --> 00:06:26,490 Let's go back and let's make the configuration in Slave Nodes as well. 53 00:06:26,510 --> 00:06:30,770 Now I'm going to modify Redis.conf File of first Slave. 54 00:06:35,310 --> 00:06:35,840 Now here 55 00:06:35,850 --> 00:06:38,180 Search for word replica. 56 00:06:51,430 --> 00:06:51,780 OK. 57 00:06:51,820 --> 00:06:59,190 So once you search with word replica, you need to come to this line where it says replica of 58 00:06:59,670 --> 00:07:02,290 And this is the place where you need to make changes. 59 00:07:02,440 --> 00:07:02,770 OK. 60 00:07:02,800 --> 00:07:06,410 So here you need to define where your Redis Master Server 61 00:07:06,690 --> 00:07:11,580 is running and what is the port on which Redis application is running. 62 00:07:12,750 --> 00:07:21,620 So in this case since it is local host. So either we can write local host or we can define the port for 63 00:07:21,630 --> 00:07:27,340 local host port is always 127.0.0.1 64 00:07:27,540 --> 00:07:31,320 And as we know our Master is going to run on Port 6 3 7 0. 65 00:07:31,320 --> 00:07:35,820 So here we need to provide the information of the port, where Master is running. 66 00:07:36,270 --> 00:07:37,150 Okay. 67 00:07:37,290 --> 00:07:41,010 So we have made the changes. Other than this change, 68 00:07:44,710 --> 00:07:52,420 the second change which we need to make is, let's also change the RDB File name and add a post fix of S 1 69 00:07:52,510 --> 00:07:58,910 So it will denote that this RDB is of Slave 1 70 00:08:09,770 --> 00:08:12,670 and again in the directoty, I'm going to change it to Redis Admin 71 00:08:18,670 --> 00:08:26,590 also we had Log file. So Log file also we can add a post fix which is S 1 and that's it. Now 72 00:08:26,590 --> 00:08:28,180 we can Save this file and Exit. 73 00:08:38,120 --> 00:08:41,920 Now we need to do the same in Redis - S 2 as well 74 00:08:57,590 --> 00:09:03,770 Okay so this is Slave Node 2 and we need to make sure Slave Node 2 is running on Port 6 3 7 2 75 00:09:11,810 --> 00:09:16,000 and log file name we can post fix _S 2 76 00:09:27,360 --> 00:09:35,110 db file name also I'm going to post fix S 2 and directory, I'm going to change it to 77 00:09:38,660 --> 00:09:39,660 /home/redisadmin 78 00:09:42,670 --> 00:09:43,690 Okay and here 79 00:09:47,460 --> 00:09:51,330 is the keyword replica of, here we need to provide information about Master. 80 00:09:57,870 --> 00:10:06,490 So since Master is running on local host. We can provide 127.0.0.1 and Port, we can change it to the Port 81 00:10:06,490 --> 00:10:10,930 on which Master is running. So it is going to run on Port 6 3 7 0 82 00:10:14,710 --> 00:10:16,480 and that's is. Now we can save and exit. 83 00:10:24,510 --> 00:10:31,140 and now similar thing we need to do here in Redis.conf of Slave 3 84 00:10:35,380 --> 00:10:37,490 So just make sure you change the port. 85 00:10:37,490 --> 00:10:39,760 It is going to run on port 6 373 86 00:10:55,510 --> 00:10:58,240 and I'm post fixing S 3 in the Log File. 87 00:11:06,770 --> 00:11:09,780 In the RDB File Name also i am post fixing S 3 88 00:11:19,680 --> 00:11:26,420 and in the Directory Name, I have changed it to /home/redisadmin and now the most important 89 00:11:26,420 --> 00:11:29,390 step is again making change in replica of. 90 00:11:29,390 --> 00:11:35,590 So by default line remains commented. You need to remove # and make it uncomment 91 00:11:35,900 --> 00:11:45,160 And then after replica of. You need to add IP address of the Master Instance and also the Port on which 92 00:11:45,170 --> 00:11:49,000 Master Redis Instance is running. So it is 6 3 7 0 93 00:11:53,950 --> 00:11:54,270 okay. 94 00:11:54,290 --> 00:11:56,010 So we have made all the changes. 95 00:11:56,030 --> 00:11:57,890 Now I would just like to verify 96 00:12:02,020 --> 00:12:03,030 by going inside 97 00:12:03,030 --> 00:12:09,670 Redis- S 1. I just want to cross-check that I had made the changes in the port 98 00:12:14,570 --> 00:12:18,240 because I think we might have just missed it. Yeah 99 00:12:18,980 --> 00:12:26,050 So what I guess we have actually missed making a change in in the Port of Slave 1. 100 00:12:26,120 --> 00:12:34,800 Okay so we have made the change in port and change the port to 6 3 7 1. 101 00:12:34,840 --> 00:12:40,090 So now if I go back to the architecture which i shown you. 102 00:12:40,180 --> 00:12:43,280 So basically we are going to have 4 Nodes. 103 00:12:43,300 --> 00:12:46,360 Master is going to run on Port 6 3 7 0. 104 00:12:46,360 --> 00:12:54,820 Then we have slave or S 1, which is going to run on Port 6 3 7 1, Slave 2 is going to run on Port 6 3 7 2 and 105 00:12:54,940 --> 00:12:57,670 slave 3 is going to run on Port 6373 106 00:13:01,020 --> 00:13:07,130 and all of these 3 slaves are going to be a Replica of Master Node. 107 00:13:16,270 --> 00:13:23,500 So let's clear the screen and let's start restarting each of the instance or starting each of the instance. 108 00:13:23,770 --> 00:13:26,520 So I'll go inside Master Directory 109 00:13:40,110 --> 00:13:48,510 and we'll start Redis server and also we need to provide path of the Configuration File and let's run it 110 00:13:48,510 --> 00:13:50,030 as a background process 111 00:13:54,330 --> 00:14:02,410 we can also verify the same by doing ps -ef and grep on the Redis name. 112 00:14:02,550 --> 00:14:06,680 Now we can see there is a Redis process which is running and using Port 6 3 7 0. 113 00:14:06,690 --> 00:14:07,970 So this is our master Node. 114 00:14:18,650 --> 00:14:28,430 Now let's go to Redis- S 1 and under the src directory, we have Redis-server and 115 00:14:28,430 --> 00:14:34,640 we also need to pass the name of the Redis.conf file and we are also going to start it as a background 116 00:14:34,640 --> 00:14:35,120 process. 117 00:14:40,290 --> 00:14:47,100 Now I see there's another Redis process which is running and it is running on 6 3 7 1 118 00:14:52,860 --> 00:14:54,940 and now let's start the remaining 2 nodes. 119 00:15:01,020 --> 00:15:04,010 So I'm going to go inside Redis- S 2 120 00:15:21,570 --> 00:15:21,980 okay. 121 00:15:22,000 --> 00:15:25,570 So now we have another Slave running which is on Port 6 3 7 2 122 00:15:49,800 --> 00:15:50,130 Okay. 123 00:15:50,140 --> 00:15:56,140 So now all our 4 instances are running and Master is running on 6 3 7 0 and slaves are running on 124 00:15:56,140 --> 00:15:59,080 6 3 7 1, 6 3 7 2 and 6 3 7 3 125 00:16:01,920 --> 00:16:07,500 Now if you remember all our logs are being stored under /tmp directory. So let's move 126 00:16:07,500 --> 00:16:09,150 on to /tmp directory. 127 00:16:11,880 --> 00:16:16,660 and here if you remember we have changed the Logs for all the Slave 1,2 and 3 128 00:16:16,680 --> 00:16:20,670 We had added up post fix of S1, S2 and S3. 129 00:16:20,670 --> 00:16:27,620 So this is how we know that these logs are coming from. This S 1 is coming from Slave 1. 130 00:16:28,170 --> 00:16:33,130 So let's see what is being displayed in this log file. 131 00:16:34,420 --> 00:16:34,710 Okay. 132 00:16:34,720 --> 00:16:37,170 So if you see the content of this log file. 133 00:16:40,640 --> 00:16:47,540 It says that this Redis instance was started and then it tried to connect to Master on this IP address 134 00:16:47,600 --> 00:16:52,370 and port 6 3 7 0 and then it was able to successfully connect 135 00:16:55,060 --> 00:16:55,740 and then. 136 00:16:55,780 --> 00:16:58,270 So basically now they both are in sync 137 00:17:03,230 --> 00:17:09,530 and if we check for Redis_S 2, we should be able to see the similar message. So here 138 00:17:09,530 --> 00:17:10,940 also we see the similar message. 139 00:17:17,820 --> 00:17:20,520 And for Redis S 3 also, we see the similar message. 140 00:17:20,970 --> 00:17:27,960 Okay so all our Slave Nodes has been successfully able to sync up with Master Node and also able 141 00:17:27,960 --> 00:17:32,520 to perform the sync up or Replication. 142 00:17:32,520 --> 00:17:49,530 Now lets say what is the logs, which is displayed in Redis Master. 143 00:17:49,560 --> 00:17:54,990 So here we see, in the Master we see that there are 3 entries. 144 00:17:55,120 --> 00:18:01,260 One is denoting that there is a Replica which is running on 6 3 7 1, Port 6 3 7 1. 145 00:18:01,270 --> 00:18:11,210 And it tried to connect to or on Made a request ofor sync request or replicate request to this Master Node. 146 00:18:11,380 --> 00:18:17,900 And then again we have the similar information for 6 3 7 2 and then we have similar for 6 3 7 3. 147 00:18:18,070 --> 00:18:19,630 So it means our Master and Slave. 148 00:18:19,630 --> 00:18:22,240 They were able to sync up properly and it was able to connect. 149 00:18:25,230 --> 00:18:30,380 Now let's connect to each of these nodes by using Redis-cli 150 00:18:31,170 --> 00:18:40,000 And by providing the port by using -p and we know our Master is running on Port 6 3 7 0 and 151 00:18:40,000 --> 00:18:41,570 if I do dbsize here. 152 00:18:41,590 --> 00:18:44,110 So right now we do not have anything in the database. 153 00:18:45,400 --> 00:18:46,090 It is blank. 154 00:18:50,630 --> 00:18:57,680 So I'll use L push command and I'll add, I'll create a key name which is called Color. 155 00:18:57,680 --> 00:19:03,380 I will add the values, which is Red, Green, Black and White. 156 00:19:03,380 --> 00:19:07,280 So we have added some Color Names to this list, which is called Color 157 00:19:10,550 --> 00:19:18,750 and now if I want to see all the values which is inside this key, which is Color. I can do lrange 158 00:19:18,780 --> 00:19:24,170 key name 0 and -1. 159 00:19:24,200 --> 00:19:31,230 So this is showing us all the values, which was available in this Key Name, which is called Color. 160 00:19:32,200 --> 00:19:34,820 Okay so this is the situation of Master Node 161 00:19:38,990 --> 00:19:40,910 and now let's exit from here. 162 00:19:41,060 --> 00:19:52,770 And let's connect to one of the Slave Nodes. So our Slave Nodes are running starting from 6 3 7 1 then 163 00:19:52,780 --> 00:19:54,760 6 3 7 2, and 6 3 7 3. 164 00:19:55,930 --> 00:20:00,020 So let's connect to 6 3 7 1 and let's do the dbsize. 165 00:20:00,670 --> 00:20:06,930 We can see we have 1 entry here, because we have only 1 List item, which is called Color. 166 00:20:08,620 --> 00:20:14,120 And if I do Keys * i can see the Key Name Color is here. 167 00:20:14,350 --> 00:20:22,570 And if I do lrange color 0 -1. We can see all the values has already been replicated 168 00:20:22,570 --> 00:20:24,250 to this Slave Node. 169 00:20:27,780 --> 00:20:32,750 Now let's exit from here and check the same in Node 6 3 7 2 170 00:20:42,960 --> 00:20:45,440 Okay so we see the same information here as well. 171 00:20:47,600 --> 00:21:03,600 Let's connect to 6 3 7 3. This is our third slave Node. 172 00:21:03,670 --> 00:21:03,980 All right. 173 00:21:03,990 --> 00:21:07,050 So here also we see the same information. 174 00:21:07,050 --> 00:21:17,000 So whatever we had added in Master Node, it has only been replicated to all the 3 Slave Nodes. 175 00:21:17,000 --> 00:21:24,850 Now let's try to, as you saw we're able to perform the Get Operations on all the Slave Nodes. So I 176 00:21:24,850 --> 00:21:33,190 can do like, i'am able to run lrange which actually giving us all the values, which is available in 177 00:21:33,190 --> 00:21:34,290 Color key. 178 00:21:34,330 --> 00:21:40,840 Now let's try to write something in this Node, in one of the slave Nodes and see if It is working. 179 00:21:40,840 --> 00:21:47,880 So I'll use Set command, and let's say we want to add a Product which is called Chair, Value is 180 00:21:47,880 --> 00:21:50,720 100 and hit enter. 181 00:21:50,740 --> 00:21:56,340 Now you see when we try to write something, something to one of the Replica Nodes. We get the error saying 182 00:21:56,860 --> 00:21:57,510 Read Only. 183 00:21:57,520 --> 00:22:06,080 You cannot write against a Read Only Replica. 184 00:22:06,130 --> 00:22:13,660 So basically you cannot perform a write operation, to a Read Only Replica but you can perform or any 185 00:22:13,660 --> 00:22:20,320 number of Users can connect to Read Only Replica and perform the Read Only Operations. 186 00:22:20,490 --> 00:22:23,210 Now let's see the process again. 187 00:22:24,000 --> 00:22:30,990 and we see we have 4 Instances of Redis running. So we will try to disconnect Master. 188 00:22:31,820 --> 00:22:32,050 OK. 189 00:22:32,100 --> 00:22:36,180 So I will shut down the services of Master 190 00:22:39,700 --> 00:22:49,210 So this is a process ID for the Master Node. So i'll do kill hyphen, kill -9 and provide the 191 00:22:49,360 --> 00:22:56,130 process ID. Hit enter and now let's check the process again. Okay. 192 00:22:56,130 --> 00:23:07,040 So now we see Master process is dead and now let's go to the Logs and see what is the error we see 193 00:23:07,040 --> 00:23:08,340 in the Slave Logs. 194 00:23:15,210 --> 00:23:15,540 okay. 195 00:23:15,560 --> 00:23:21,970 Now we see on the Slave 1, I'm able to see that there is connection refused errors. 196 00:23:22,490 --> 00:23:30,100 Similarly if I go to Redis_S 2, which is Slave 2 log. Here also we see the same error 197 00:23:36,850 --> 00:23:39,930 and in the Third Slave Node also, we get the same error. 198 00:23:40,680 --> 00:23:40,930 Okay. 199 00:23:40,950 --> 00:23:47,790 So if Master is down, Replicas are still running. It is going to give us error, that it is not able 200 00:23:47,790 --> 00:23:48,790 to sync with Master. 201 00:23:48,790 --> 00:23:55,170 However it doesn't mean that you cannot connect to Slave Nodes and you cannot perform Read Only Operation. 202 00:23:55,170 --> 00:24:01,050 So you still can connect to all the Slave Nodes and you can still carry on performing the Read Only 203 00:24:01,050 --> 00:24:04,640 Operations. 204 00:24:05,200 --> 00:24:07,390 So I will connect to one of the Slave Nodes again 205 00:24:18,430 --> 00:24:25,610 and here if you see, I'm still able to connect to Slave Node, which is running on 6371 and I'm able 206 00:24:25,620 --> 00:24:32,110 to perform all the Read Only Operations. So that's all about Redis Replication.