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So in this session we are going to discuss about Redis Clustering.  So Redis Clustering needs a minimum



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of six servers.  In order for you to set up Redis Cluster.



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Okay.



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The reason why we need six servers are, we need  minimum of 3 Masters and we need  minimum of 3



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Slaves.



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So here you see on the screen, we have Master one and then we have Master two and Master three.



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And each of these masters are replicating its data to its corresponding slaves.



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Now what happens when a Master goes down.  Ok when a Master goes down in that case its corresponding Slave



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is going to become the Master and the Cluster will continue working.



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Now what happens at the same time one of the Slave Node goes down.



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So basically Slave Node goes down, there is not going to be any change.



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Everything is going to continue working as it is.  Only when the Master is down, Slave takes care of the



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role of Master.



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However if a Slave goes down, you do not notice anything.



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Now let's talk about some of the key points of Redis Clustering.



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So as you see here Redis Cluster is a Multiple Master Architecture.



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So basically we have multiple masters and now we are no longer limited to the ability of having a Single



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Master.  Unlike we had in the case of Sentinels and internally data is partitioned into 16000 buckets



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and each server keeps or holds some number of buckets.



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So in this case since we had three servers. 16000 buckets are going to be divided by 3 because that's



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the total number of Master Nodes we have.



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And then whatever the number comes, that is the number which each of them Master Node is going to hold



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In terms of buckets.



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So what happens when you perform a write operation.



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So when you perform a write  operation.  Keys # values determined



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And that's how they come to know which is the Master Server,  which is holding that data.



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So again this is internal working and this is something that you don't need to worry about.



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This is how data is or how the processing is taken care internally.



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So basically your data is partitioned into total number of available nodes.



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Now if we talk about pros of setting up

Redis Cluster.



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So basically you can see this is highly scalable and it has the ability to scale up to 1000 nodes. Performance



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in Redis Cluster is very good,  because you have Multiple Masters and if  one of them master goes down,  the



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other Slave is going to take care of the role of Master.  Now when we talk about some of the Cons.



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So basically we need  minimum of 6 Servers,  in order to set up a Cluster.



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OK.



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If you are having one node or only two nodes, in that case you won't be able to set up a Cluster.



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So from the Infrastructure Point of view,  Yes,  you need more number of servers,  in order to set up Redis



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Cluster.



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And once you are on Redis cluster and you want to downgrade to Redis Sentinel or whatever.



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You won't be able to do that.



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So once you are on Redis cluster,  you have to stay on Redis cluster.  So in next session we will discuss



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about setting up Redis Cluster and we will also set up Redis Cluster in a demo environment and we will



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see how it is going to function.