redis

sudo apt update
sudo apt install redis-server

OR

sudo apt-get update
sudo apt-get install build-essential tcl
curl -O http://download.redis.io/redis-stable.tar.gz     # or     wget http://download.redis.io/redis-stable.tar.gz
tar xzvf redis-stable.tar.gz
cd redis-stable
make
make test
sudo make install


Update redis config, allow manage Redis as a service
===================================================
sudo nano /etc/redis/redis.conf
supervised systemd


Configuring a Redis Password
============================
sudo nano /etc/redis/redis.conf
requirepass <password>

Reload the redis service to adapt the new changes made on the configuration file.
sudo systemctl reload redis

Validate Status
===============
sudo systemctl status redis



Stop\Start Redis
================
/etc/init.d/redis-server stop
/etc/init.d/redis-server start

OR

sudo service redis-server start
sudo service redis-server stop
sudo service redis-server restart

OR

sudo systemctl restart redis

running the server manually with config

 /usr/bin/redis-server /etc/redis/redis.conf

Test the Redis Instance Functionality
=====================================
redis-cli ping
OR
redis-cli -a <password> ping
OR

redis-cli -h redis15.localnet.org -p 6390 ping

it should answer with PONG, but in some cases it can answer with "LOADING Redis is loading the dataset in memory"


How to fix "LOADING Redis is loading the dataset in memory"?
1) sudo service redis-server stop
2) delete redis dump and temp files from /var/lib/redis/
3) /etc/init.d/redis-server start



Uninstall redis
sudo apt-get --purge remove redis-server
sudo rm -rf /etc/redis/dump.rdb





How to flush Redis cache and delete everything using the CLI?

redis-cli flushall

How to Browse/View The Values Stored in Redis?

Redis Commander allow web view of redis DB

Install it using 

npm install -g redis-commander

Activate the web-server using 

redis-commander  --redis-password <Password>

Solve Redis Errors

Problem 1

PHP Fatal error:  Uncaught RedisException: MISCONF Redis is configured to save RDB snapshots, but it is currently not able to persist on disk. Commands that may modify the data set are disabled, because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option). Please check the Redis logs for details about the RDB error.

Solution

 nano /etc/redis/redis.conf

On redis.conf line ~235 let's try to change config like this

- stop-writes-on-bgsave-error yes
+ stop-writes-on-bgsave-error no

Problem 2

 

# WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.

# WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.

Solution

sudo nano /etc/sysctl.conf

# Add at the bottom of file
vm.overcommit_memory = 1
net.core.somaxconn=1024

Now for these configs to work, you need to reload the config

sudo sysctl -p

Problem 3

# WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.

Solution

sudo nano /etc/rc.local

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
    echo never > /sys/kernel/mm/transparent_hugepage/enabled
fi