Integrating another stat extension in Powa

Clone the repository:

git clone https://github.com/powa-team/powa-archivist/
cd powa-archivist/
make && sudo make install

Any modification to the background-worker code will need a PostgreSQL restart.

In order to contribute another source of data, you will have to implement the following functions:

snapshot:

This function is responsible for taking a snapshot of the data source data, and store it somewhere. Usually, this is done in a staging table named powa_my_data_source_history_current. It will be called every powa.frequency seconds. The function signature looks like this:

CREATE OR REPLACE FUNCTION powa_my_data_source_snapshot() RETURNS void AS $PROC$
...
$PROC$ language plpgsql;

aggregate:

This function will be called after every powa.coalesce number of snapshots. It is responsible for aggregating the current staging values into another table, to reduce the disk usage for PoWA. Usually, this will be done in an aggregation table named powa_my_data_source_history. The function signature looks like this:

CREATE OR REPLACE FUNCTION powa_my_data_source_aggregate() RETURNS void AS $PROC$
...
$PROC$ language plpgsql;

purge:

This function will be called after every 10 aggregates and is responsible for purging stale data that should not be kept. The function should take the powa.retention global parameter into account to prevent removing data that would still be valid.

CREATE OR REPLACE FUNCTION powa_my_data_source_aggregate() RETURNS void AS $PROC$
...
$PROC$ language plpgsql;

unregister:

This function will be called if the related extension is dropped.

Please note that the module name used in the powa_functions table has to be the same as the extension name, otherwise the function will not be called.

This function should at least remove entries from powa_functions table. A minimal function would look like this:

CREATE OR REPLACE function public.powa_my_data_source_unregister() RETURNS bool AS
$_$
BEGIN
    DELETE FROM public.powa_functions WHERE module = 'my_data_source';
        RETURN true;
END;
$_$
language plpgsql;

Each of these functions should then be registered:

INSERT INTO powa_functions (module, operation, function_name, added_manually)
VALUES  ('my_data_source', 'snapshot',   'powa_mydatasource_snapshot',   true),
        ('my_data_source', 'aggregate',  'powa_mydatasource_aggregate',  true),
        ('my_data_source', 'unregister', 'powa_mydatasource_unregister', true),
        ('my_data_source', 'purge',      'powa_mydatasource_purge',      true);