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Version: Develop

a9s Harbor SPI Configuration

This document describes a9s harbor SPI configuration.


Custom Parameter Configuration

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

The a9s Harbor 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 harbor SPI configuration. The platform operator has to configure the property harbor-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:

default_value: 600
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 Harbor.

NameDefault valueIs modifiable

The parameter max_connections sets the PostgreSQL configuration parameter max_connections to the configured number.

Valid values are any integer bigger than 0. For practical reasons, it should be at least 20.

IMPORTANT: It makes sense to configure this parameter per plan. For a9s Harbor, it doesn't make sense to let the application developer fine-tune this value.

There is no silver bullet to calculate max_connections. Please take a look at the a9s PostgreSQL SPI configuration parameter documentation to get a grasp how it could be calculated.

Example Configuration

Let's build an imaginary example.

The default value for the max_connections custom parameter should be 600. The custom parameter max_connections should not be allowed to be changed by the application developer.

Then the configuration must look the following way:

default_value: 600
modifiable: true

Per Plan Configuration

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


Additional custom parameters will be made available over time. We do not make all available custom parameters the SPIs knows about 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.