🚀 Redis Cluster

📌 Introduction

This repository contains a brief documentation of my Redis Cluster exercise. The following steps were completed in this project:

• ✅ Setting up a Redis Cluster
• ✅ Configuring Geographic Partitioning
• ✅ Conducting Failover and Performance Tests

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🛠️ Step 1: Initial Setup

To create a realistic lab environment, I used Docker to simulate multiple servers in a network, each running a Redis instance. To keep things simple, I designed a basic network structure, documented below:

🌍 IP Addressing Schema

Instance Name	IP Address
redis_master_asia	10.0.10.1
redis_master_eu	10.0.10.2
redis_master_us	10.0.10.3
redis_replicant_asia	10.0.10.4
redis_replicant_eu	10.0.10.5
redis_replicant_us	10.0.10.6

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⚡ Creating the Cluster

Normally, redis-cli should automatically assign the correct master-replica pairs, but in my case, it didn't, so I configured them manually:

redis-cli --cluster create 10.0.10.1:7000 10.0.10.2:7000 10.0.10.3:7000 --cluster-yes
redis-cli --cluster add-node 10.0.10.4:7000 10.0.10.1:7000 --cluster-slave
redis-cli --cluster add-node 10.0.10.5:7000 10.0.10.2:7000 --cluster-slave
redis-cli --cluster add-node 10.0.10.6:7000 10.0.10.3:7000 --cluster-slave

To verify the cluster status, use:

redis-cli -p 7000 cluster nodes

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🔍 Slot Verification & Issue Identification

To ensure our keys are correctly distributed across nodes, we use the {eu}, {us}, and {asia} prefixes.

redis-cli -p 7000 CLUSTER KEYSLOT {asia}:test
redis-cli -p 7000 CLUSTER KEYSLOT {eu}:test
redis-cli -p 7000 CLUSTER KEYSLOT {us}:test

Example output:

(integer) 8971 # {asia}
(integer) 6893 # {eu}
(integer) 14680 # {us}

To check which node is responsible for each slot, run:

redis-cli -p 7000 -c CLUSTER SLOTS

📊 Slot Distribution Table

Node	Slot Range
redis_master_asia	0 - 5460
redis_master_eu	5461 - 10922
redis_master_us	10923 - 16383

However, based on the key slot values, there is a misalignment:

(integer) 8971      -> redis_master_eu (❌ Should be in redis_master_asia)
(integer) 6893      -> redis_master_eu (✅ Correct)
(integer) 14680     -> redis_master_us (✅ Correct)

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🔧 Fixing Slot Alignment

To fix this issue, we need to migrate the slots to their correct nodes.

🔹 Master Node Identifiers

redis_master_asia -> cca08c426f25595c7fa0bde1f5e2b4ea0ab118a8
redis_master_eu -> c33e50b331faf63597d9267f28f8e75edf0a861e
redis_master_us -> 8a6324404e5e64bffa32a6c5e705283c896f6bc7

🔹 Commands to Migrate Slots

redis-cli -p 7000 -c CLUSTER SETSLOT 8971 IMPORTING cca08c426f25595c7fa0bde1f5e2b4ea0ab118a8 # on redis_master_asia
redis-cli -p 7000 -c CLUSTER SETSLOT 8971 MIGRATING c33e50b331faf63597d9267f28f8e75edf0a861e # on redis_master_eu
redis-cli -p 7000 -c CLUSTER SETSLOT 8971 NODE cca08c426f25595c7fa0bde1f5e2b4ea0ab118a8 # on redis_master_asia

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🏆 Verification: Key Distribution Test

Now, we will test whether the keys are correctly placed in their respective nodes.

redis-cli -p 7000 -c SET {eu}:demo "this_is_a_demo"
redis-cli -p 7000 -c SET {asia}:demo "this_is_a_demo"
redis-cli -p 7000 -c SET {us}:demo "this_is_a_demo"

To check key placement, run:

redis-cli -p 7000 -c KEYS *demo*

✅ Expected Outputs

On redis_master_us

redis-cli -p 7000 -c KEYS *demo*
1) "{us}:demo"

On redis_master_eu

redis-cli -p 7000 -c KEYS *demo*
1) "{eu}:demo"

On redis_master_asia

redis-cli -p 7000 -c KEYS *demo*
1) "{asia}:demo"

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👁 Sentinel Setup

Now we setup three different sentinel instances (one for each region, even though they will supervise all instances). The configuration file for the sentinel instances looks like this:

port 5000

sentinel monitor redis_master_asia 10.0.10.1 7000 2
sentinel monitor redis_master_eu 10.0.10.2 7000 2
sentinel monitor redis_master_us 10.0.10.3 7000 2

sentinel down-after-milliseconds redis_master_asia 5000
sentinel failover-timeout redis_master_asia 10000
sentinel parallel-syncs redis_master_asia 1

sentinel down-after-milliseconds redis_master_eu 5000
sentinel failover-timeout redis_master_eu 10000
sentinel parallel-syncs redis_master_eu 1

sentinel down-after-milliseconds redis_master_us 5000
sentinel failover-timeout redis_master_us 10000
sentinel parallel-syncs redis_master_us 1

Using my sandbox it is enough to also just run the docker-compose script, since it will add the sentinel versions anyway. When you stop a master redis instance you can see in the logs of the sentinel instance, that it gave the role to the master e.g.

🎯 Conclusion

With these configurations and tests, we now have a fully functional Redis Cluster with proper geographic key distribution. 🚀🎉

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💡 This documentation serves as a guide for setting up and troubleshooting Redis Clusters with geographic partitioning.