Hi everyone, today Redis is the subject of our article, we are going to install it on CentOS 7. Build sources files, install the binaries, create and install files. After installing its components, we will set its configuration as well as some operating system parameters to make it more reliable and faster.
Redis is an open source multi-platform data store written in ANSI C, that uses datasets directly from memory achieving extremely high performance. It supports various programming languages, including Lua, C, Java, Python, Perl, PHP and many others. It is based on simplicity, about 30k lines of code that do "few" things, but do them well. Despite you work on memory, persistence may exist and it has a fairly reasonable support for high availability and clustering, which does good in keeping your data safe.
There is no official RPM package available, we need to build it from sources, in order to do this you will need install Make and GCC.
Install GNU Compiler Collection and Make with yum if it is not already installed
yum install gcc make
Download the tarball from redis download page.
curl http://download.redis.io/releases/redis-3.0.4.tar.gz -o redis-3.0.4.tar.gz
Extract the tarball contents
tar zxvf redis-3.0.4.tar.gz
Enter Redis the directory we have extracted
Use Make to build the source files
Enter on the src directory
Copy Redis server and client to /usr/local/bin
cp redis-server redis-cli /usr/local/bin
Its good also to copy sentinel, benchmark and check as well.
cp redis-sentinel redis-benchmark redis-check-aof redis-check-dump /usr/local/bin
Make Redis config directory
Create a working and data directory under /var/lib/redis
mkdir -p /var/lib/redis/6379
In order to Redis work correctly you need to set some kernel options
Set the vm.overcommit_memory to 1, which means always, this will avoid data to be truncated, take a look here for more.
sysctl -w vm.overcommit_memory=1
Change the maximum of backlog connections some value higher than the value on tcp-backlog option of redis.conf, which defaults to 511. You can find more on sysctl based ip networking "tunning" on kernel.org website.
sysctl -w net.core.somaxconn=512.
Disable transparent huge pages support, that is known to cause latency and memory access issues with Redis.
echo never > /sys/kernel/mm/transparent_hugepage/enabled
Redis.conf is the Redis configuration file, however you will see the file named as 6379.conf here, where the number is the same as the network port is listening to. This name is recommended if you are going to run more than one Redis instance.
Copy sample redis.conf to /etc/redis/6379.conf.
cp redis.conf /etc/redis/6379.conf
Now edit the file and set at some of its parameters.
Set daemonize to no, systemd need it to be in foreground, otherwise Redis will suddenly die.
Set the pidfile to redis_6379.pid under /var/run
Change the network port if you are not going to use the default
Set your loglevel.
Set the logfile to /var/log/redis_6379.log
Set the directory to /var/lib/redis/6379
Here are some actions that you can take to enforce the security.
In many cases, the client application resides on the same machine as the server, so there is no need to listen do network sockets. If this is the case you may want to use unix sockets instead, for this you need to set the port option to 0, and then enable unix sockets with the following options.
Set the path to the socket file
Set restricted permission to the socket file
Now, to have access with redis-cli you should use the -s flag pointing to the socket file
redis-cli -s /tmp/redis.sock
You may need remote access, if so, you should use a password, that will be required before any operation.
Imagine the output of the next command. Yes, it will dump the configuration of the server, so you should deny access to this kind information whenever is possible.
CONFIG GET *
To restrict, or even disable this and other commands by using the rename-command. You must provide a command name and a replacement. To disable, set the replacement string to "" (blank), this is more secure as it will prevent someone from guessing the command name.
rename-command FLUSHDB "FLUSHDB_MY_SALT_G0ES_HERE09u09u"
rename-command FLUSHALL ""
rename-command CONFIG "CONFIG_MY_S4LT_GO3S_HERE09u09u"
By default Redis will periodically dump its datasets to dump.rdb on the data directory we set. You can configure how often the rdb file will be updated by the save command, the first parameter is a timeframe in seconds and the second is a number of changes performed on the data file.
Every 15 hours if there was at least 1 key change
save 900 1
Every 5 hours if there was at least 10 key changes
save 300 10
Every minute if there was at least 10000 key changes
save 60 10000
The /var/lib/redis/6379/dump.rdb file contains a dump of the dataset on memory since last save. Since it creates a temporary file and then replace the original file, there is no problem of corruption and you can always copy it directly without fear.
Starting at boot
You may use systemd to add Redis to the system startup
Copy sample init_script to /etc/init.d, note also the number of the port on the script name
cp utils/redis_init_script /etc/init.d/redis_6379
We are going to use systemd, so create a unit file named redis_6379.service under /etc/systems/system
Put this content, try man systemd.service for details
Description=Redis on port 6379
Now add the memory overcommit and maximum backlog options we have set before to the /etc/sysctl.conf file.
vm.overcommit_memory = 1
For the transparent huge pages support there is no sysctl directive, so you can put the command at the end of /etc/rc.local
echo never > /sys/kernel/mm/transparent_hugepage/enabled
That's enough to start, with these settings you will be able to deploy Redis server for many simpler scenarios, however there is many options on redis.conf for more complex environments. On some cases, you may use replication and Sentinel to provide high availability, split the data across servers, create a cluster of servers. Thanks for reading!