Deploy a 3‑Master‑3‑Slave Redis Cluster Without Pitfalls

Environment specifications: three virtual machines (2 CPU/2 GB each) running Rocky 9.7, IPs 192.168.1.200‑202, deployment directory /app/redis-cluster, master port 7000, replica port 7001 (cluster bus ports 17000‑17001).

1. Environment preparation (run on all nodes)

1.1 Disable firewall and SELinux

# Disable firewall
systemctl stop firewalld
systemctl disable firewalld

# Disable SELinux
setenforce 0
sed -i 's/^SELINUX=enforcing$/SELINUX=disabled/' /etc/selinux/config

1.2 Install build dependencies

yum install -y gcc gcc-c++ make wget tar

1.3 Create deployment directory and redis user

# Create redis user
useradd -s /sbin/nologin redis

# Create deployment directories
mkdir -p /app/redis-cluster/{7000,7001}/{data,log}
chown -R redis:redis /app/redis-cluster

2. Compile and install Redis from source (all nodes)

2.1 Download Redis source

cd /usr/local/src
wget https://download.redis.io/releases/redis-7.2.4.tar.gz
tar -zxf redis-7.2.4.tar.gz

2.2 Build and install

cd redis-7.2.4
make MALLOC=libc
make PREFIX=/app/redis install

2.3 Configure environment variables

echo 'export PATH=$PATH:/app/redis/bin' >> /etc/profile
source /etc/profile

# Verify installation
redis-cli --version

3. Write Redis configuration files (all nodes)

3.1 Master node configuration (port 7000)

cat > /app/redis-cluster/7000/redis.conf << EOF
# Basic settings
bind 0.0.0.0
port 7000
daemonize yes
pidfile /app/redis-cluster/7000/redis.pid
logfile /app/redis-cluster/7000/log/redis.log
dir /app/redis-cluster/7000/data

# Memory settings – volatile‑lru
maxmemory 512mb
maxmemory-policy volatile-lru

# Cluster settings
cluster-enabled yes
cluster-config-file nodes-7000.conf
cluster-node-timeout 15000
cluster-require-full-coverage no

# Persistence
appendonly yes
appendfilename "appendonly-7000.aof"
save 900 1
save 300 10
save 60 10000

# Security
requirepass "redis123"
masterauth "redis123"
EOF

3.2 Replica node configuration (port 7001)

cat > /app/redis-cluster/7001/redis.conf << EOF
# Basic settings
bind 0.0.0.0
port 7001
daemonize yes
pidfile /app/redis-cluster/7001/redis.pid
logfile /app/redis-cluster/7001/log/redis.log
dir /app/redis-cluster/7001/data

# Memory settings – allkeys‑lru (recommended for 2 GB machines)
maxmemory 512mb
maxmemory-policy allkeys-lru

# Cluster settings
cluster-enabled yes
cluster-config-file nodes-7001.conf
cluster-node-timeout 15000
cluster-require-full-coverage no

# Persistence
appendonly yes
appendfilename "appendonly-7001.aof"
save 900 1
save 300 10
save 60 10000

# Security
requirepass "redis123"
masterauth "redis123"
EOF

3.3 Adjust file permissions

chown -R redis:redis /app/redis-cluster

4. Start all Redis instances (all nodes)

# Start master instance
su -s /bin/bash redis -c "/app/redis/bin/redis-server /app/redis-cluster/7000/redis.conf"

# Start replica instance
su -s /bin/bash redis -c "/app/redis/bin/redis-server /app/redis-cluster/7001/redis.conf"

# Verify processes
ps -ef | grep redis

5. Create the Redis cluster (run on any node, e.g., 192.168.1.200)

5.1 Cluster creation command

redis-cli -a redis123 --cluster create \
192.168.1.200:7000 192.168.1.201:7000 192.168.1.202:7000 \
192.168.1.200:7001 192.168.1.201:7001 192.168.1.202:7001 \
--cluster-replicas 1

5.2 Confirm creation

When prompted, type yes and press Enter.

Can I set the above configuration? (type 'yes' to accept): yes

5.3 Expected success output

[OK] All nodes agree about slots configuration.
>>> Check for open slots...
>>> Check slots coverage...
[OK] All 16384 slots covered.

6. Verify cluster status

6.1 View node information

redis-cli -c -a redis123 -h 192.168.1.200 -p 7000 cluster nodes

Three master nodes (marked with master)

Three replica nodes (marked with slave and pointing to their masters)

All 16384 hash slots assigned

6.2 Check cluster health

redis-cli -a redis123 --cluster check 192.168.1.200:7000

6.3 Test write and read

# Connect to the cluster
redis-cli -c -a redis123 -h 192.168.1.200 -p 7000

# Write test keys
set testkey testvalue
set key1 value1
set key2 value2

# Read test keys
get testkey
get key1
get key2

# Find the slot of a key
cluster keyslot testkey

7. Configure automatic start (all nodes)

7.1 Service file for port 7000

cat > /etc/systemd/system/redis-cluster-7000.service << EOF
[Unit]
Description=Redis Cluster 7000
After=network.target

[Service]
Type=forking
User=redis
Group=redis
ExecStart=/app/redis/bin/redis-server /app/redis-cluster/7000/redis.conf
ExecReload=/bin/kill -USR2 $MAINPID
ExecStop=/app/redis/bin/redis-cli -a redis123 -p 7000 shutdown
Restart=always
RestartSec=5
PrivateTmp=true

[Install]
WantedBy=multi-user.target
EOF

7.2 Service file for port 7001

cat > /etc/systemd/system/redis-cluster-7001.service << EOF
[Unit]
Description=Redis Cluster 7001
After=network.target

[Service]
Type=forking
User=redis
Group=redis
ExecStart=/app/redis/bin/redis-server /app/redis-cluster/7001/redis.conf
ExecReload=/bin/kill -USR2 $MAINPID
ExecStop=/app/redis/bin/redis-cli -a redis123 -p 7001 shutdown
Restart=always
RestartSec=5
PrivateTmp=true

[Install]
WantedBy=multi-user.target
EOF

7.3 Enable and start services

systemctl daemon-reload
systemctl enable redis-cluster-7000 redis-cluster-7001
systemctl start redis-cluster-7000 redis-cluster-7001

# Verify status
systemctl status redis-cluster-7000 redis-cluster-7001

8. Common cluster operation commands

8.1 View cluster information

redis-cli -c -a redis123 -h 192.168.1.200 -p 7000 cluster info

8.2 Manual failover test

# Trigger failover on a replica
redis-cli -a redis123 -h 192.168.1.200 -p 7001 cluster failover

# Check node state changes
redis-cli -c -a redis123 -h 192.168.1.200 -p 7000 cluster nodes

8.3 Backup cluster data (caution for very large databases)

# Run on each node
redis-cli -a redis123 -p 7000 bgsave
redis-cli -a redis123 -p 7001 bgsave

# Backup files are stored in /app/redis-cluster/7000/data/ and /app/redis-cluster/7001/data/

9. Production‑grade configuration (64 GB example)

Key adjustments: memory allocation, persistence policy, kernel tuning, security hardening, and cluster parameters.

9.1 Full production config for master (port 7000)

# Basic settings
bind 192.168.1.200 127.0.0.1
port 7000
daemonize yes
pidfile /app/redis-cluster/7000/redis.pid
logfile /app/redis-cluster/7000/log/redis.log
dir /app/redis-cluster/7000/data
loglevel notice

# Memory settings
maxmemory 24gb
maxmemory-policy volatile-lru
activedefrag yes
active-defrag-ignore-bytes 100mb
active-defrag-threshold-lower 10
active-defrag-threshold-upper 100

# Persistence
save 900 1
save 3600 100
rdbcompression yes
rdbchecksum yes
stop-writes-on-bgsave-error yes
appendonly yes
appendfilename "appendonly.aof"
appendfsync everysec
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 1gb
no-appendfsync-on-rewrite yes
aof-use-rdb-preamble yes

# Network
tcp-backlog 1024
timeout 300
tcp-keepalive 300
maxclients 10000

# Client output buffers
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit replica 2gb 1gb 60
client-output-buffer-limit pubsub 32mb 8mb 60

# Cluster
cluster-enabled yes
cluster-config-file nodes-7000.conf
cluster-node-timeout 10000
cluster-require-full-coverage no
cluster-migration-barrier 1

# Replication
repl-diskless-sync yes
repl-diskless-sync-delay 5
repl-ping-replica-period 10
repl-timeout 60

# Security
requirepass "Redis@Prod2024!StrongPass"
masterauth "Redis@Prod2024!StrongPass"
rename-command FLUSHDB "RedisFlushDB_Prod2024"
rename-command FLUSHALL "RedisFlushALL_Prod2024"
rename-command KEYS "RedisKeys_Prod2024"
rename-command CONFIG "RedisConfig_Prod2024"
rename-command SHUTDOWN "RedisShutdown_Prod2024"
rename-command DEBUG ""

The replica (port 7001) uses the same file with port, pidfile, logfile, dir, and cluster-config-file values changed to 7001.

9.2 System kernel optimizations (all nodes)

9.2.1 Kernel parameters

cat >> /etc/sysctl.conf << EOF
# Redis‑specific tuning
vm.overcommit_memory = 1
vm.swappiness = 0
net.core.somaxconn = 1024
net.ipv4.tcp_max_syn_backlog = 1024
net.core.netdev_max_backlog = 1024
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
EOF

# Apply changes
sysctl -p

9.2.2 File descriptor limits

cat >> /etc/security/limits.conf << EOF
redis soft nofile 65535
redis hard nofile 65535
redis soft nproc 65535
redis hard nproc 65535
EOF

9.2.3 Disable Transparent Huge Pages (THP)

# Temporary disable
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag

# Permanent disable
cat >> /etc/rc.local << EOF
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag
EOF
chmod +x /etc/rc.local