# Requirements

Redis database, used by the CKEditor Collaboration Server needs to meet software and hardware requirements presented in the database requirements article.

# Supported Redis options

The minimal supported Redis version in 3.2.6.

Supported Redis modes:

  • Redis single instance
  • Redis Cluster

# Connecting to Redis

To connect to the Redis at least the REDIS_HOST needs to be set. Domain names, IPv4 and IPv6 are supported.

REDIS_HOST                               - required (for Redis single instance connection)
REDIS_PORT                               - optional (default: 6379)
REDIS_DB                                 - optional (default: 1)
REDIS_PASSWORD                           - optional
REDIS_USER                               - optional
REDIS_IP_FAMILY                          - optional (required only when using an IPv6 domain as `REDIS_HOST`)

If you are using a database that only supports IPv6 and you want to refer to that database via its domain name, then the IP version needs to be selected manually.

To do so, you need to set the REDIS_IP_FAMILY environment variable to 6.
It will force CKEditor Collaboration Server On-Premises to use an IPv6 connection.

# Connecting to Redis Cluster

To set up the connection with a Redis Cluster, nodes need to be provided as the REDIS_CLUSTER_NODES variable.

REDIS_CLUSTER_NODES        - required (for Redis Cluster connection)
REDIS_IP_FAMILY            - optional (required only when using an IPv6 domain in `REDIS_CLUSTER_NODES`)

The REDIS_CLUSTER_NODES needs to contain a list of nodes in the dedicated format, which consists of:

"IP:PORT:[optional PASSWORD],IP:PORT:[optional PASSWORD]"

To understand the connection string format, check the examples below:

# IPv4

# IPv4 with a password

# IPv6
REDIS_CLUSTER_NODES: "[0:0:0:0:0:0:0:1]:7000,[0:0:0:0:0:0:0:1]:7001,[0:0:0:0:0:0:0:1]:7002"

# IPv6 with a password
REDIS_CLUSTER_NODES: "[0:0:0:0:0:0:0:1]:7000:password1,[0:0:0:0:0:0:0:1]:7001:password2,[0:0:0:0:0:0:0:1]:7002:password3"

# Domain name

# Domain name with IPv6 support

# Domain name with a password

# TLS Connection and certificates

  • If your Redis server is configured to require SSL connections, you can use REDIS_TLS_CA, REDIS_TLS_KEY, and REDIS_TLS_CERT to pass certificates to the Redis client.
  • If you are connecting Collaboration Server On-Premises with a Redis instance hosted on AWS ElastiCache and Encryption in-transit is enabled, then you need to set the REDIS_TLS_ENABLE environment variable to true. There is no need to pass TLS certificates to make an encrypted connection.
  • If you are connecting to AWS ElastiCache Cluster with TLS enabled you also need to set REDIS_DISABLE_DNS_LOOKUP to true.
REDIS_TLS_CA                             - optional
REDIS_TLS_KEY                            - optional
REDIS_TLS_CERT                           - optional
REDIS_TLS_ENABLE                         - optional (default: false)
REDIS_DISABLE_DNS_LOOKUP                 - optional (default: false)

You can provide the certificates in two ways:

# Passing certificates as files

To pass a certificate as a file you need to provide the path to it, which is available inside of the application container.

REDIS_TLS_CA: /var/cs/tls/ca.crt
REDIS_TLS_CERT: /var/cs/tls/redis.crt
REDIS_TLS_KEY: /var/cs/tls/redis.key

It may require configuring volumes, to make the used files available under the path provided to the REDIS_TLS_* variables.

# Passing certificates as text

Another way of providing the required certificates is by providing them as text.


The DATABASE_SSL_CERT can be provided in three formats:

  • as a one-liner, where new lines should be represented by a newline character (\n).
  • in the original certificate format using the Literal Block Scalar character (|).
  • as a base64 encoded string. It could solve problems related to newline character encoding by cloud hosting platforms.

# Connecting to Redis Enterprise Cloud

Redis Enterprise Cloud expects users to use the Redis database index of 0. By default, Collaboration Server On-Premises uses Redis database index 1. You may thus encounter the ERR DB index is out of range error.

To fix it, change the database index using the environment variable:


# Root certificates rotation

Various cloud providers e.g. Azure, AWS rotate their root certificates periodically, it may require manual certificate updates by the system administrator to keep the application up and running.

Read a detailed article about the case in the Azure documentation

# Redis High availability

To ensure high availability of Redis, we recommend using Redis in Cluster mode with at least 3 nodes (must be an odd number of nodes) and using the master-replica model, which means that the number of servers increases to 6. In this configuration, every node should have at least 2 cores and 2 GB of RAM.

Please note that when using Redis Cluster you must run applications with the correct configuration, which is described here.

# Next steps