Service Integration

This article is for other extension developers

If you are developing an extension that runs a service (similar to how omni_httpd is, this section describes the basics of service integration.

Service Registration

Services are recorded in the services table and can be registered using register_service(name [, info]) function. If a service with such a name already exists, only info will be updated.

The services are recorded in the services table:

Name	Type	Description
name	text	The unique name of the service
info	jsonb	Additional metadata or configuration details about the service
postmaster_start_time	timestamptz	The timestamp when the database server started (used with name as the primary key in services)

postmaster_start_time allows us to distinguish services registered after postmaster has been restarted. It is populated automatically.

This is typically not necessary as services are cleaned up after every registration to only contain the current "epoch".

However, if relevant trigger (service_provisioning_trigger) has been disabled, the records are kept and this allows to discern registrations.

Operations

In order to integrate your service into omni_service, you need to add triggers to service_operations to observe the operations and enact appropriate actions.

create function service_operation() returns trigger
    language plpgsql
as
$$
begin
    case
        when new.operation = 'stop' then call my_service.stop();
        when new.operation = 'start' then call my_service.start();
        else null;
        end case;
    return new;
end;
$$;

create or replace trigger my_service_operations
    after insert
    on service_operations
    for each row
execute function service_operation();