Installing Redis
For this article, the focus is going to be on setting up redis on Ubuntu and Centos running systemd. Redis comes with a single server instance. Running multiple redis servers with the intent of optimizing and parallelizing your requests requires setting up additional redis servers. This can be easily accomplished with a few modifications. Start with installing redis for the chosen distribution.
Ubuntu
$ sudo apt-get install redis-server -y
Centos
$ sudo yum install redis -y
Please Note: The remainder of this article will focus on Ubuntu’s default directory structure for replacing the default redis, but these changes can be applied and run within a Centos environment also. The default redis directory structure for Ubuntu configuration files is /etc/redis/redis.conf, and with Centos it is /etc/redis.conf. Please adjust any necessary commands.
Disabling the default Redis server
Once redis is installed, or if it is already installed on the system, then the default redis-server service needs to be stopped and disabled. This can be done utilizing systemctl.
$ sudo systemctl stop redis-server
$ sudo systemctl disable redis-server
Redis server configurations
Creating redis configurations that have clear identifiers is ideal. An example of this would be hosting a redis server to manage sessions, and another redis server to manage caching. Use simple file names to label these services. Examples of this would be /etc/redis/redis-cache.conf and /etc/redis/redis-sessions.conf. Let’s step into creating the new redis directory structure and configurations.
Please Note: Some of these directory structures might exist already depending on the chosen distribution.
$ sudo mkdir -p /etc/redis/{redis-server.pre-up.d,redis-server.post-down.d,redis-server.post-up.d,redis-server.pre-down.d}
$ sudo mkdir -p /var/lib/{redis-cache,redis-sessions}
Next, the creation of the primary configuration files is necessary. Create a copy of the default redis configuration and add a service identifier. Replicate this process for each redis server that needs to be setup, utilizing a different identifier. This guide will setup two redis servers for cache and sessions.
$ sudo cp /etc/redis/redis.conf /etc/redis/redis-cache.conf
$ sudo cp /etc/redis/redis.conf /etc/redis/redis-sessions.conf
There are a few settings that will require adjustment with the redis configuration files. When deciding which ports to run each redis server on, this decision is at the system administrator’s discretion. I start with port 6380, and increment by one from there. Additionally, restricting the amount of memory that redis is allowed to utilize is a good idea when running multiple redis servers.
port {{{port:6380}}}
maxmemory 2147483648
pidfile /var/run/redis/redis-{{{identifier:cache}}}.pid
logfile /var/log/redis/redis-{{{identifier:cache}}}.log
dir /var/lib/redis-{{{identifier:cache}}}
Running redis with a password requirement is never a bad idea. This can easily be accomplished by setting a random password within the configuration file.
$ sudo sed -i "/#\ requirepass/c\requirepass $(date +%s|sha256sum|base64|head -c 32 ; echo)" /etc/redis/redis-cache.conf
$ sudo sed -i "/#\ requirepass/c\requirepass $(date +%s|sha256sum|base64|head -c 32 ; echo)" /etc/redis/redis-sessions.conf
Configuring and enabling systemd services
The primary systemd configuration files for redis will live in /lib/systemd/system. Anything that is required in /etc/systemd/system will be symlinked when the services are enabled through systemctl. With any choice of editor, create the service files for systemd. Start with the creation of /lib/systemd/system/redis-cache.service from the below template. The service identifier is editable so that you can also create your sessions service.
[Unit]
Description=Advanced key-value store
After=network.target
Documentation=http://redis.io/documentation, man:redis-server(1)
[Service]
Type=simple
ExecStart=/usr/bin/redis-server /etc/redis/redis-{{{identifier:cache}}}.conf
PIDFile=/var/run/redis/redis-{{{identifier:cache}}}.pid
TimeoutStopSec=0
Restart=always
User=redis
Group=redis
ExecStartPre=-/bin/run-parts --verbose /etc/redis/redis-server.pre-up.d
ExecStartPost=-/bin/run-parts --verbose /etc/redis/redis-server.post-up.d
ExecStop=-/bin/run-parts --verbose /etc/redis/redis-server.pre-down.d
ExecStop=/bin/kill -s TERM $MAINPID
ExecStopPost=-/bin/run-parts --verbose /etc/redis/redis-server.post-down.d
PrivateTmp=yes
PrivateDevices=yes
ProtectHome=yes
ReadOnlyDirectories=/
ReadWriteDirectories=-/var/lib/redis-{{{identifier:cache}}}
ReadWriteDirectories=-/var/log/redis
ReadWriteDirectories=-/var/run/redis
CapabilityBoundingSet=~CAP_SYS_PTRACE
# redis-server writes its own config file when in cluster mode so we allow
# writing there (NB. ProtectSystem=true over ProtectSystem=full)
ProtectSystem=true
ReadWriteDirectories=-/etc/redis
[Install]
WantedBy=multi-user.target
Alias=redis-{{{identifier:cache}}}.service
Starting Redis servers
Once the configuration files have been built, it’s time to enable and start each redis service.
$ sudo systemctl enable redis-cache.service redis-sessions.service
Created symlink from /etc/systemd/system/redis-cache.service to /lib/systemd/system/redis-cache.service.
Created symlink from /etc/systemd/system/multi-user.target.wants/redis-cache.service to /lib/systemd/system/redis-cache.service.
Created symlink from /etc/systemd/system/redissessions.service to /lib/systemd/system/redis-sessions.service.
Created symlink from /etc/systemd/system/multi-user.target.wants/redis-sessions.service to /lib/systemd/system/redis-sessions.service.
$ sudo systemctl start redis-cache.service redis-sessions.service
After the services have been started, check the status of the services to ensure they are running as intended, and confirm that the redis ports are accepting connections.
$ sudo systemctl status redis-cache.service redis-sessions.service
● redis-cache.service - Advanced key-value store
Loaded: loaded (/lib/systemd/system/redis-cache.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2019-01-24 11:28:47 CST; 24h ago
Docs: http://redis.io/documentation,
man:redis-server(1)
Main PID: 1214 (redis-server)
CGroup: /system.slice/redis-cache.service
└─1214 /usr/bin/redis-server 127.0.0.1:6380
Jan 24 11:28:47 example.com systemd[1]: Starting Advanced key-value store...
Jan 24 11:28:47 example.com run-parts[1172]: run-parts: executing /etc/redis/redis-server.pre-up.d/00_example
Jan 24 11:28:47 example.com run-parts[1203]: run-parts: executing /etc/redis/redis-server.post-up.d/00_example
Jan 24 11:28:47 example.com systemd[1]: Started Advanced key-value store.
● redis-sessions.service - Advanced key-value store
Loaded: loaded (/lib/systemd/system/redis-sessions.service; enabled; vendor preset: enabled)
Active: active (running) since Thu 2019-01-24 11:28:47 CST; 24h ago
Docs: http://redis.io/documentation,
man:redis-server(1)
Main PID: 1213 (redis-server)
CGroup: /system.slice/redis-sessions.service
└─1213 /usr/bin/redis-server 127.0.0.1:6379
Jan 24 11:28:47 example.com systemd[1]: Starting Advanced key-value store...
Jan 24 11:28:47 example.com run-parts[1164]: run-parts: executing /etc/redis/redis-server.pre-up.d/00_example
Jan 24 11:28:47 example.com run-parts[1200]: run-parts: executing /etc/redis/redis-server.post-up.d/00_example
Jan 24 11:28:47 example.com systemd[1]: Started Advanced key-value store.
$ sudo ps aux|grep redis|grep -v grep
redis 1208 0.0 0.0 38856 3184 ? Ssl Jan24 0:52 /usr/bin/redis-server 127.0.0.1:6380
redis 1214 0.0 0.0 38856 3108 ? Ssl Jan24 0:51 /usr/bin/redis-server 127.0.0.1:6381
Cleanup
If interested in performing cleanup of the default server so that there is no confusion, remove the following files if they exist.
/etc/redis/redis.conf
/etc/systemd/system/redis.service
/lib/systemd/system/redis.service