a9s Redis SPI Configuration

This document describes a9s Redis SPI configuration.

Custom Parameter Configuration

The a9s Redis SPI handles custom parameters for all service instances. It does configuration and validation of custom parameters.

The a9s Redis SPI defines default values for certain custom parameters. Also, it defines whether a custom parameter can be set by the application developer.

The platform operator can overwrite those choices by changing the a9s Redis SPI configuration. The platform operator has to configure the property redis-spi.service_instance.custom_param_config. The property value must be a hash. Every key in that hash stands for a custom parameter and the value for every key contains the configuration for that particular parameter.

The configuration for a particular param is a hash consisting of the following optional keys: default_value and modifiable. The key default_value specifies the default value for that parameter and modifiable specifies whether the application developer is allowed to set that custom parameter. For example:

redis-spi:
  service_instance:
    custom_param_config:
      maxclients:
        default_value: 6000
        modifiable: false

Default Custom Parameter Configuration

The following table contains custom parameters that are configurable by the platform operator. The meaning of those custom parameters can be read in the application developer documentation for a9s Redis.

Name	Default value	Is modifiable	Version Compatibility
lazyfree-lazy-eviction	'no'	true	all
lazyfree-lazy-expire	'no'	true	all
lua-time-limit	5000	true	all
maxclients	10000	true	all
maxmemory-policy	'volatile-lru'	true	all
maxmemory-samples	5	true	all
notify-keyspace-events	''	true	all
failover-timeout	30000	true	all
down-after-milliseconds	10000	true	all
stop-cluster-update-on-failure	true	false	all
cluster-update-node-timeout	10	false	all
tls-protocols	null	true	all
tls-ciphers	null	true	all
tls-ciphersuites	null	true	all
hostname-resolution	'disabled'	true	>= 7

tls-protocols

The parameter tls-protocols corresponds to the Redis configuration parameter tls-protocols.

tls-ciphers

The parameter tls-ciphers corresponds to the Redis configuration parameter tls-ciphers. This parameter sets the list of ciphers used for TLS 1.2 and below.

a9s Redis SPI does no validation for the tls-ciphers value except that it must be of type string or null (do not set tls-ciphers in redis.conf and sentinel.conf).

tls-ciphersuites

The parameter tls-ciphersuites corresponds to the Redis configuration parameter tls-ciphersuites. This parameter sets the list of ciphers used for TLS 1.3 and above.

a9s Redis SPI does no validation for the tls-ciphersuites value except that it must be of type string or null (do not set tls-ciphers in redis.conf and sentinel.conf).

hostname-resolution

For more information, refer to the hostname-resolution section of the Application Developer's documentation.

Example Configuration

Let's build an imaginary example.

The default value for the maxclients custom parameter should be 600. The custom parameter lua-time-limit should also have a default value of 600 and the application developer should not be allowed to change it.

Then the configuration must look the following way:

redis-spi:
  service_instance:
    custom_param_config:
      maxclients:
        default_value: 600
        modifiable: true
      lua-time-limit:
        default_value: 600
        modifiable: false
      failover-timeout:
        default_value: 30000
        modifiable: true
      down-after-milliseconds:
        default_value: 10000
        modifiable: true

Per Plan Configuration

Take a look at Service Plans documentation if you want to configure the custom parameters per plan.

Notes

Additional custom parameters will be made available over time. We do not make all available custom parameters the SPIs know available to the platform operator from the beginning.

During the SPI startup, the configuration the platform operator made will be checked. When it's invalid, the SPI will not start up.

redis-spi.protocols

For more details on this property, please refer to the a9s Framework TLS configuration documentation.