So in this session we are going to learn about setting up Cluster. In this example I'm going
to take 3 Nodes. So Node 1, which is going to be Master node and then there are 2 more Nodes, which are
going to be Slave Nodes.
So in total we have 3 nodes or 3 Servers. So IP address or Server 1
is 10.128.0.2 and Host name is itpanther01 and then we have Slave Nodes, which is IP
address is 10.128.0.4, Host name is itpanther02 and then the third Node is 10.128.0.5
and Host name is itpanther03. So initially when we are going to set up the Cluster. First Node is
going to be Master and then when Master is going down then one of the Slave Nodes is going to be
promoted to Master and this thing is going to be taken care by Sentinel.
Okay.
So we are going to set up Redis and plus Sentinel on each of these Nodes.
So Sentinel is already bundled with the software, which you download, when you download Redis. So if
you remember in our first example, I had already downloaded the Software. So I have that software and then
we are going to extract this software and we will go on to configure. So before we start configuration.
Just wanted to verify all the IP addresses, which we have shown here.
So these are the same thing which we have here.
So let me clear the screen and let's begin with verifying the Host name.
So you can verify that first server is itpanther01 and this is the IP address and then I'm going to use
ssh command to log in to Server or Slave Nodes.
If you use Host name, it is going to give you the host name of the Server. If you use Host name -i
It is going to show you the IP address.
So this is one of our Slave Nodes.
and now I'm going to log in to Second Slave Node
okay.
So these are the servers, which we have and we are able to log into all the servers.
Now also just to show you that initially we do not have any, you know, software available in any of
the Slave Nodes.
So this is the home directory of the Slave Node and we do not have any software available.
So we are going to copy the software from Master Server to both the Slave Nodes.
So I'm going to clear the screen and let me also exit because right now if you see I'm on Node 3 which
is indicated by here itpanther03. So I will do Exit and I'll be back to server 1
Okay.
Now if we do ls-lrt, we see this is a software which we have downloaded and let me extract this
software
okay.
Now we see Redis-stable folder. So inside Redis-stable folder
If you do ls-lrt again, you will see we have Redis.conf and also we have a
Sentinel.conf. OK.
So Redis.conf is going to be used for all the configuration with respect to Redis and
Sentinel.conf, is going to be used for all the configuration related to Sentinel
and also if you go inside src folder
and here if you do a ls-lrta
OK initially if you do ls-lrta, you will not see.
you know, Redis-server or Redis-Sentinel utility because this is just the uncompiled
version.
So first we need to compile this.
So right now we are in Redis-stable directory. Let me clear the screen and this is the position
where we are right now.
So we are Redis-stable folder
And here if you remember, to make the, to compile this. We need to run Make command.
So run Make command and hit enter.
It is going to take a couple of minutes because it is going to prepare the binaries, which we are going
to use to run a Sentinel and also Redis server.
So whatever setup we are going to do.
Now it is going to be a production like setup.
OK.
The same thing you can follow in the Production Environment.
So usually what I do is, I compile the software at one of the servers and then we do not need to do the
same activity on other servers.
We can just copy paste the same software.
OK.
which is compiled one.
So now you see it is already, the software is compiled and we would have Binaries now. Lets do
ls-lrt and now if we go inside src folder again and do ls-lrt. This time we can see
we have Redis-server and also we have a Redis-Sentinel.
So Redis-server is going to be used to start Redis server and also Redis-Sentinel will
be used to start Sentinel.
and both of these you know, utilities accept configuration file.
So Redis-server, we are going to pass Redis.conf file while starting Redis server and
to Redis-Sentinel, we are going to pass Sentinel.conf file. So that is why it is important
we set up a Configuration File correctly before starting
both of these services.
So I am going one level back and if we do ls-lrt, here we have
Redis.conf and Sentinel.conf.
So let's start by setting up configuration for Redis.conf
And remember currently we are on the Master Node. So whatever configuration we are doing, it is for the
Master Node.
So I'm opening Redis.conf in VI Editor
and now if you scroll down, first thing we need to change is the buying address.
Okay.
So by default it is showing 127.0.0.1
So this one we need to change to the actual IP address of the server, on which Redis instance is
going to run.
So this is Master Node. So for this one, we need to put the IP address of the Master Node.
So here I have made the change and put the IP address of the Master Node
and the second thing we can also make change in the log file. So a Log file
Usually I keep at /tmp directory.
So I'm going to give location of /tmp/redis.log
So on the Master Node, under the /tmp directory. There is going to be a file created Redis.log
that is going to hold all the logs related to Redis database and if you scroll further down,
Now we need to
okay.
So now you can search Replica of, but make sure that on the Master Server, you do not make any changes
here in the Replica of. In the Master Server, we don't need to make any changes here.
And on the Slave Nodes, we are going to make changes here and going to update the Master IP address and
Port Number here.
Okay.
So
for now on the Master Node, we are done.
We don't need to make any other changes here.
So save and Exit and now let's make changes in the Sentinel.conf File.
so here
also first thing you need to do is, change this Bind Address and by default it is, if it is commented
you can uncomment
and remove whatever default IP addresses are given.
And since we are making Configuration on muster.
So here we need to be the IP address of the Master.
okay.
So the IP address for that is 10.128.0.2
This is a very important step.
So always make sure we have the correct IP address updated here.
Otherwise your Redis server or
and also you're Redis Sentinel may not be able to communicate with each other with Slave Nodes.
Okay.
So that is going to be very complicated, once you end up into issues and it is going to be very difficult
to troubleshoot, especially when you are doing it for the first time.
So always make sure you have the correct IP address updated in the Bind
and for Sentinel, I'm going to change the log file to /tmp/sentinel.log
If you have seen, we have not made any changes in the port. So default Port for Redis is 6 3 7 9 and
for Sentinel it is 2 6 3 7 9. Okay.
So this is going to be same
on all the nodes
okay.
Now we have made the basic changes which was required on the
Master Node.
I think I'm missing one thing here.
So let's go to Sentinel.conf file
again and here I think we missed one thing, which was related to Sentinel Monitor.
Okay.
So this is again important thing here.
You specify the IP address of your Master Node.
So here we know Master node is going to be 10.128.0.2 and this is the Master Node which
is going to be the Initial Master Node. After that Sentinel is going to decide on its own that and
Sentinel is going to elect a new master in case existing master goes down and after the IP address we
have Port number.
So as we know, we have not made any changes and default Redis runs on 6 3 7 9.
So the same port is given here as well and this name My Master Name is the logical name. If you want to
change it, it can be changed as well.
In my case I'm not going to change it.
However, when you are doing the same thing in the Production, based on the Organization Naming Structure
or Naming Standards, you may need to change this.
and after the Port, we have the count of the Quorum which is set to number 2. So the count of the Quorum
specify, this is the minimum number of Sentinel Nodes, which need to agree, whenever they are going to
make any decision.
So the decision can be that whether the Master is down or not.
And which of the Slave Node, should become the new Master.
Okay so these are the decisions which Sentinel is going to make and minimum of 2 sentinel servers
has to agree in order to make one of the existing Slave and promoted into a Master.
So when you make any changes here with respect to the name My Master.
So make sure you also need to make changes for the same name in the other lines as well.
So this name, whatever name you give here should also be matching in the other name.
Which you can see here, like it is set up here or here.
In my case I have not made any changes. Okay so that's why I don't need to make any changes in the
names.
Now the other important thing is, here you see Sentinel down after milliseconds
and here you specify the name of the Master Node.
So basically here we are telling that after how many seconds Sentinel is going to say that
Okay Master node is down and it is going to work towards promoting one of the Slave Nodes to make them
a Master. okay.
So by default it is set to 30000 milliseconds which is equal to 30 seconds.
So again depend on the design which you want to set up in the Production Environment.
You may increase or decrease the value here.
Right now we are just going to leave it to default which is 30 seconds
okay so that's it here.
Now I think we are good.
So I have saved and exited from here. Okay so we have done the kind of basic configuration for this node.
Now I'm going to copy the software to the other nodes.
And also make sure once you copy the software to other nodes,
You need to make changes related to the IP address on the other nodes.
Okay so let's see that.
Let me clear the screen first and go one step back.
So I'm going to use scp command.
So scp command
is used to transfer files from one server to another server.
So in this case I want to copy this complete directory. So that's why I have given scp -r which
is recursive and then we need to specify the server, where we want to copy this, you know, directory or files.
So in this case it is going to be itpanther02, which is one of the Slave Nodes.
You can also specify the IP address but usually it is easier to specify the Host name
and then this ~/ is actually specifying that, we need to copy this Redis-stable
to the home directory
okay.
So on this Server
Redis Admin's home directory. This Redis-stable is going to get copied.
Okay so let's hit enter.
okay.
So yeah we missed to specify the directory, which we want to copy. So that's why we got the error
So this is the correct syntax. So use give scp -r the directory, which you want
to copy along with the sub-directories and files and then you give that Host name, from where you want to
copy and also if you want to copy under any other user, you can also specify that User Name here.
Whatever User Name you want to copy it to. If you do not specify any user here, on the server where you
are trying to copy. This software it is going to copy the same user name.
Okay.
So in this case I already have Redis Admin user name created on all the Slave nodes as well. So
we may not need to specify the User Name here. Again so the fundamental here is, that we are copying this
Redis -stable software from Master Nodes to Slave Nodes. You may use WinSCP or any other
mechanism to copy this software from one server to another.
So I'm just using SCP here and let's hit enter.
Now the File Copy is in progress and File Copy has been completed.
Now let's also copy this software on Third Node, which is itpanther03. So I have changed the host name
here, remaining all. Everything remains the same.
Hit Enter.
Okay so now software has been copied.
Now we will log in one by one to the Slave Nodes and also we will correct the configuration changes
which we have set up for Master Node.
Okay so Master Node is done.
Now let's log into Slave Node, which is itpanther02
and here if I do a ll or ls-lrt. You can do whatever command you like.
And now we can see, we have Redis-stable folder here.
So if we go inside Redis-stable and we open,
Redis.conf. Okay the same thing whatever configuration which we have done on Master node, has been
copy pasted here on the other nodes.
However, as we know this is itpanther02
So here this IP address is going to be different.
Okay.
So in the Bind, make sure you have the correct IP address.
So this IP address should be, the IP address on which you are going to run this
Redis instance.
Okay.
So in this case it is going to be 10.128.0.4, because this is server itpanther02
and the benefit we got from making the Configuration, Basic Configuration, initially and then copy pasting
on other node is, that here we will, we see we already have a Log File specified. We do not need to, you know,
make the same changes here as well.
So the only change we needed to make was, related to bind and the other thing is, we also need to make
a change in the replica of.
So on the Master Node, we have not touched this section.
However when you are working on the Slave Node, you need to provide the Master IP address, in the
Replica of section.
Okay.
So here we know our Master is running on, 10.128.0.2 and also it is running on default port which
is 6 3 7 9
okay.
So that's it.
We can now save it and exit and now let's make changes in Sentinel.conf
Again first thing is you need to change
Bind Address. Since this software is going to run on server 4. So I have changed it to, change the IP address
accordingly and Log File,
we don't need to make any changes. So on this server again Log is going to be stored under /tmp
So now we have kind of standard. So across all the nodes including Master and the Slave Nodes, Redis
Logs and Sentinel Logs are going to be stored inside /tmp directory.
Also if you now see, in Sentinel we already have, you know correct configuration because whatever we did
in the case of Master, the same thing has to be done on the other node.
So we do not need to make any changes here.
Okay.
So the only change which we have made in Sentinel.conf File is, we have changed the Bind Address and also
provided the correct IP address of this server.
And now we can save and exit. Okay so now we have done the configuration on Slave Node as well.
Now let's move on to the second Slave Node
So I'm going to do ssh itpanther03 and now if we do ll, we can see we have the directory
here.
Let's go on to this directory.
and let's
Make the changes in Redis.conf
So here in the bind, please provide the correct IP address of this server which is, in my case going to
be 10.128.0. 5 because this is server 3
Oh, I'm sorry. It has to be changed to 5. Ok
You can see here.
So this is the Host name and this is IP address.
So the same I have copy pasted here.
Log file is going to remain same.
We don't want to make any changes here.
And now we need to make changes near the replica of section.
So here I'm going to uncomment
and let's provide the master IP address which is 10.128.0. 2 and the port on which master is running
is the default port which is 6 3 7 9.Okay.
So that's it.
Now we can save and exit and now let's make changes in Sentinel.conf
Here the only change, which we need to make is, we need to change this Bind Address to point to the correct
IP address.
So it is going to be 10.128.0. 5. Save and exit
okay.
So from configuration wise we are good.
We have done all the configuration.
So just a quick recap.
We have downloaded the software on Node 1.
Then we did some initial configuration on Node 1, Redis.conf and Sentinel.conf and then
we copy the same software to other Slave Node and we also change the Bind Address to point to the correct
IP address on both the configuration file, which is Redis.conf and Sentinel.conf
Now we are going to start Redis on all the nodes. So let me go to Node 1
OK let me clear the screen.
So Host name and Host name-i
So you can see right now we are on the Master Node
and we are here at this directory /home/redisadmin.
So let's start Redis Server
by using command Redis-server and then
we need to pass the Redis.conf file here.
And also I will use & because I want to run this service as a background service
so that's it.
Hit enter.
And also now we can run Sentinel by using Redis-sentinel
and here we need to provide full path of Sentinel.conf, use &
Hit enter. Okay.
So now if you want to see the logs of Redis server and Redis Sentinel, you can go on to tmp directory.
So we know that we have stored logs at, tmp/redis.log
Okay.
So Redis logs are this directory. So, I'm using tail to see the logs.
Okay so we can see it is saying that it is Ready to accept connections.
So seems Master has started properly and we can also verify the same by checking for sentinel.log
okay.
So here also it seems to be okay.
So on Node 1, we have started Redis and also Sentinel.
Now I'm going to move on to Node 2
and here also we will start Redis and also Sentinel. So everything will remain the same.
Just make sure when you are starting Sentinel, you use Redis-sentinel.
Do not use Redis-server.
okay.
So we have started on Slave Node as well. Let's check the logs by doing tail-f, tail space -f
and going to /tmp/. For Redis Log
we need to go to Redis.log
All right so here now we see, when we started Slave node, we could see that it is saying, Master and Replica
has synced.
So basically when we started a Slave node, it was able to connect to Master node and they were Master
and you know, Slave were able to connect and Master was able to replicate all the data from Master to Slave
node.
So this looks fine to me.
Now we can see the log of
Sentinel.
So here also we can see that it has added the child node, which is slave node to
10.128.0.4
This is a node, which we started and Sentinel has detected that one more node has been added to the
Redis Cluster.
OK so this also looks good.
And now we can do the same thing on server 3.
So I will clear the screen and let me log into Server 3, which is itpanther03 and IP address is
10.128.0.5
Okay.
And now we need to start Redis.
now we need to start Sentinel.
Okay just be careful when you are doing for the first time. Do it slowly.
Especially when you are doing on the Production Environment. Okay.
So here also we have started Redis and we have also started Sentinel. So let's see the logs.
Okay on this note also everything seems to be okay and Master and Replica both synced and both looks
to be in good shape.
Let's check the logs of Sentinel.
okay.
So here also we can see everything is looking okay.
And you can see there is one entry, which is saying +Slave which means Sentinel has detected that one more Slave
has been added to the Cluster.
Okay.
Which is you can verify the IP address.
So now we have two Slaves.
one is 10.128.0.4, the other one is 10.128.0.5
okay.
So now, right now I'm still on Node 3, which is, you can verify by using Host name -i
you see the IP address and now to connect to Redis Client, now we need to use Redis-cli
and you know you don't need to switch over to servers by using, Redis-cli. You can pass the
Host name to which you want to connect to and also you can specify the Port.
Okay so if I want to connect to Master Node, I can specify
Redis-cli-h and IP address of the Master Node. So -h signifies Host here.
So we know our Master is running on 10.128.0.2 and it is running on Port 6 3 7 9. So
that's how we connect to you know, from one of the the client, we can connect to any number of Redis
server. We just need to provide the Host name and the correct Port number.
So right now we are connected to Master Node and let's see since this is a new Setup, we should not have
any data here. As we can see dbsize giving value of 0. If we do Keys * we get empty list.
So basically right now there is nothing
in our Redis Cluster.
Let me exit from here and let's connect to one of the Slave Nodes. So Slave Nodes are running on Node
4 and 5.
So I have changed the IP address and here also we can verify the same.
Okay we do not see any data here
and you can verify the same one Node 5
okay.
So everything is good now.
Now let's connect to Master node again.
So I'm going to provide IP address of Master node and now we will write some data and we should be able
to see this data on the Slave Nodes.
So I will do L push.
I will provide some Color values.
Okay hit enter. So we have a set up 5 values or we have actually written a key with 5 values.
Okay.
If I do L range, key name 0 -1. I see all the 5 values here on the Master Node. Now lest's connect
to Slave Nodes and let's verify the same. Okay whether the data has replicated or not.
So I'm going to connect to Node 4
and here.
If we do L range, key name, which is Color. Starting position is 0. Ending position is -1, which means
it is going to give us all the value of this List and we can see on the Slave Node also, we get
the same output.
Let's connect to other slave node.
okay here
also, we can verify. We get the same output.
So it means Redis cluster has been set up properly and master and slaves are in sync.
And whatever we write to Master, we are able to, Master is able to replicate to all the Slave Nodes.
Now what happens when you try to write anything on the
Slave Nodes.
So right now we are still logged into the Slave node.
And if I do set and some key name, let's say Product and we specify Chair. Hit enter.
You see we get error that It is only a Read Only Node. we cannot write any data to Slave Nodes.
So this also proves that this is a Slave Node, which we are connected to.
Now I'm going to exit from here. Clear the screen.
Now we will learn the way how to connect to Redis Sentinel.
So for this one, you still use Redis-cli utility
and you use -h to specify the Host name.
Since we are running Sentinel on all the 3 nodes. So you can connect to any of the 3 nodes by
specifying the -h and correct Host name.
Okay.
So let's say we want to connect to 10.128.0.2, which is you know, the server where our Master
Redis is running on.
And also we need to specify the Port we are using -P and Sentinel runs on Port 2 6 3 7 9, by default.
And we haven't made any changes. So we can connect to Sentinel by using Port 2 6 3 7 9. In case you have
made any changes.
So you need to specify the correct Port number here.
So hit enter.
Now we are connected to Sentinel.
So there are many commands related to Sentinel, which you can use to monitor or do various other actions
In this one we,
since this session is all about setting up clusters. So we are just going to stick to setting up Cluster
and we will just use couple of commands of Sentinels.
So here if you want to see what is, you know, information. So you use Sentinel
space Master and specify the logical Master node. So if you remember in Redis.conf, we had a
name, which is called My Master and we hadn't made any changes there.
So logical name is going to remain the same, which is going to be called My Master.
So this is our Cluster Name
you know you can,
Yeah you can take it as a Logical Cluster Name but actually it is pointing to the Master.
Okay.
So if you hit enter
Now you can see all the information, which is provided by Sentinel.
So right now if you see, Sentinel knows that you know, name of the Master is My Master and it is running on IP
10.128.0.2 and the port on which it is running is this
and the runid is also provided here.
And the more important thing, if you scroll down, you can see on Line number 21, that we have down after
milliseconds, which is set to 30000 milliseconds, which is equal to 30 seconds.
And also if you look at bit down, you can see the total number of Slaves is shown as 2. So Sentinel
is correctly able to figure out, that how many Master Node or how many Slave Nodes are connected.
So it has shown 1 Master Node at the top and it also knows that there are 2 Slave Nodes, which are
you know, part of this Cluster and also on Line number 33, you can see it is talking well number of other
Sentinels.
So not only Sentinel knows that how many Master and Slave Nodes are running. This also knows how many different
Sentinels are running. So other than this Sentinel, it also know that there are 2 more Sentinels are
running. Okay and number of Quorums are specified as 2
So it means there are 2 Sentinels instances they have to agree.
You know whenever one of the Master is down and then they are going to elect a New Master from one
of the existing Slaves.
Okay
so now let's exit from here.
So if you see now, we are on Master node and here let's.
Yeah.
So what I will do now, we will shut down the Master Node services of Redis on Master node and we will
see how Sentinel is going to detect that Master Node is down and it is going to promote a New Node,
you know one of the Slave Nodes to the Master Node.
So first thing is we would like to see the Logs.
Okay.
While this is happening. So let's log into one of the Slave Nodes.
okay.
This is a Slave Node and here we will open Sentinel Logs.
So when we are shutting down services on Master node, we should be able to see the logs in the real time.
so we know what is happening behind the scene.
Okay so we know our Sentinel Logs are stored at /tmp/sentinel.log
And if you hit enter, you can see the Logs.Okay.
Now I'm going to open a new instance
okay.
So basically this is again the Masters,
Master node and I had just opened a new session. So you can verify the same using Host name -i
And this is the IP address of the master node. So here we are going to shut down the services of a Master
Node. So now there are two ways to shut down Master Node. If you want to shut down the services,
Redis services gracefully. You can use Redis-cli and you can provide the name which is
10.128.0.2 and provide the Port number, which is 6 3 7 9.
And here you can write the command which is called Shut Down.
Okay so it is going to shut down the Master Node. However since this is not a you know, we want to simulate
a Production scenario and typically in a Production scenario service will, service may go down abruptly,
when the server goes down.
So we can just use ps-ef command to kill the Redis service
So here we can see that this server is running on Port 6 3 7 9 and this is a process ID. So I will
use kill command. kill -9 and the process ID.
So this is going to kill Redis Master Node. So once you do that, within 30 sec, we should be able to see
you know, some changes happening here and Sentinels should be able to detect that Master is down and
it should be able to promote one of the existing Slave Nodes to a Master Node. So let's see how this
works.
So I'm back here.
Now I'm going to hit enter and if we do ps-ef grep Redis.
We can see we have only Redis Sentinel running but there is no Redis Server running.
So Redis Server is down . Okay let's clear the screen and let's wait for around 20 more seconds.
Because our setting is set to 30 seconds. So Sentinel is going to take 30 seconds to make sure
that it is down. As we can see now Sentinel is into action.
It has displayed so many logs.
So basically what it is doing here is, if you try to understand the Log.
So yeah, from here actually we can see that it is saying that
+sdown.
So basically what that means is you can see here +sdown.
So basically it has detected that Master is down and it is now trying the failover. You can see the
logs here and then it is trying the action, which is called Vote for Leader.
Okay.
So this is where you know, a minimum of 2 Sentinel nodes has to Vote and Agree and choose a, you know,
Node which can become Master.
Okay.
So here you can see they have said Elected leader master, which is
currently it is pointing to this Master Node and now if you see here, we can see here it has promoted
one of the Slave Node, which is 10.128.0.4 as the Master Node.
and also if you see at the bottom, now you can see,
if you look at here. You can see that IP address, 10.128.0.5 is still a Slave.
And also the previous master node which was running on 10.128.0.2 has now turn into a Slave
Node.
OK.
Now we can actually log into Node 4 which is 10.128.0.4, which has become Master Node.
Okay and let's perform a Set operation to make sure that we are able to write something because Master,
on Master node we should be able to do the write operations.
Okay so I'm going to enter a Product Value or a Product Name in this case.
Okay.
So once I hit enter, you can see it is, if I make it a bit bigger you can see it has replied with.
Okay.
Which means it is now accepting our write request.
So I will exit from here and what we will do is, let's start Redis Server again and see what happens
when Redis Server is started or
What is the action which Sentinel is going to take.
Right now if you see there is still a Line which is saying +sdown. So +sdown means is, one
of the Slave is down and this is the IP address of the Slave, which is down. Okay.
So it should be changing to -s down. Once we bring up the server again okay.
So once we bring up the previous Master up again. It is not going to be promoted to Master.
You know it is still going to be a Slave.
So this will continue to work as a slave as long as you know, none of the node goes down. So this
node which is running on, 10.128.0.4 will continue to work as a Master.
Okay so let's start Redisdb on
Master node again.
I mean Previous Master Node.
Okay hit enter and now you can see, as soon as we hit enter, services started here.
There is a new entry came which is saying -sdown Slave. So means now it has detected that Slave
node is up again.
Okay.
This is the same Slave Node which was previously Master. So this also verifies that our Master or our
Cluster is working fine, because Master Slaves are able to connect to each other, able to reply to each
other.
Let's also see the value you know, which we have inserted in, by connecting to new master node is replicated
now to this Slave Node, which was down and now it has come up.
Okay.
So let's see
one second.
So yeah let me clear the screen first.
So I will use Redis-cli using -h, we will specify the Host which we want to
connect to.
So we want to connect to 10.128.0.4, which is the New Master.
Oh I'm sorry, this case we should be connecting to 10.128.0.2, which is the Slave Node which has
just started now.
Okay.
And Port is going to be 6 3 7 9 and if we do Get product. Now we can see that we have got the product
value. So this node was previously a master node. It went down, then Sentinel made, one of the existing
Slave Node, a master node which is 10.128.0.4
And then we brought this node back again and this node is now going to continue to act as Slave Node.
okay.
So that's all about setting up Cluster in a Production Environment and making your Redis in a,
I mean running in a High Availability Mode.