Configuring the Installation
This section details many aspects of the OS and Redis Enterprise Software configurations necessary.
CentOS / RHEL7 distributions have, by default, a restrictive firewall mechanism based on firewalld (which in turn configures the standard iptables system). The default configuration assigns the network interfaces to the public zone and blocks all ports, except 22 (SSH). Redis Enterprise Software (RS) installation on CentOS / RHEL 7 automatically creates two firewalld system services: A service named redislabs, which includes all ports and protocols needed for communications between cluster nodes.
There are two default locations for the socket files: /tmp - In clean installations of RS version lower than 5.2.2 /var/opt/redislabs/run - In clean installations of RS version 5.2.2 and higher We made this change because some customers have maintenance procedures that delete the /tmp directory. When you upgrade from a RS version lower than 5.2.2 to 5.2.2 and higher, the socket files are not moved to the new location by default.
Note: mDNS is not supported for use with production environments and should only be used in dev/test environments. If you choose to use the mDNS protocol when setting the cluster name (for details, refer How to set the cluster name, make sure that the configurations and prerequisites, which are required for resolving databases' endpoints, are met. These configurations and perquisites are needed on the client machines, as well as on the machines you are using as Redis Enterprise Software (RS) nodes if you are using the Replica of feature.
Swap space is used by the Linux OS to help manage memory (pages) by copying pages from RAM to disk and the OS is configured by default to be fairly aggressive. For Redis Enterprise Software (RS) with the way it utilizes and manages memory, it is best to eliminate the likelihood of the OS swapping. If you would like to understand why, please read more on how RS manages memory for best functionality and performance in the section below.
DNS is critical to the default operation of Redis Enterprise Software (RS) deployments. This can be altered, but instead using the Discovery Service, which utilizes pure IP based connectivity as it is compliant with the Redis Sentinel API. As part of the high availability capabilities in RS, each node includes a small DNS server for managing various internal cluster functionalities, such as automatic failover or automatic migration. Therefore, the node on which you are provisioning RS should not run any other DNS server except for the one included with the RS installation.