Currently, admin app requests service statistics (with notification
counts grouped by status) and template statistics (with counts by
template) in order to display the service dashboard.
Service statistics are gathered from FactNotificationStatus table
(counts for the last 7 days) combined with Notification (counts for
today).
Template statistics are currently gathered from redis cache, which
contains a separate counter per template per day. It's hard for us
to maintain consistency between redis and DB counts. Currently it
doesn't update the count for cancelled letters, counter resets in
the middle of the day might produce a wrong result for the rest of
the week and cleared redis cache can't be repopulated for services
with low data retention periods).
Since FactNotificationStatus already contains separate counts for
each template_id we can use the existing logic with some additional
filters to get separate counts for each template and status combination,
which would allow us to populate the service dashboard page from one
query response.
If a precompiled letter can't be opened (e.g. because it isn't a valid
PDF) we were setting its billable units to 0, but not moving it to the
invalid PDF bucket. If a precompiled letter failed sanitisation, we were
moving it to the invalid PDF bucket but not setting its billable units
to 0.
This commit makes sure that we always set the billable units to 0
and move the PDF to the right bucket if it fails sanitisation or can't be
opened.
now that we're reading from two tables (ft_notification_status and
notifications) for stats, we'll get a couple of rows for each
notification type. If a service doesn't have any rows in one of those
tables, the query will return a row with nulls for the notification
types and counts. Some services will have history but no stats from
today, others will have data from today but no history.
This commit acknowledges that any row might have nulls, not just the
first row.
Flask-SQLAlchemy paginate function issues a separate query to get
the total count of rows for a given filter. This query (with
filters used by the API integration Message log page) is slow for
services with large number of notifications.
Since Message log page doesn't actually allow users to paginate
through the response (it only shows the last 50 messages) we can
use limit instead of paginate, which requires passing in another
flag from admin to the dao method.
`count` flag has been added to `paginate` in March 2018, however
there was no release of flask-sqlalchemy since then, so we need
to pull the dev version of the package from Github.
The query follows the same pattern as the other queries, getting the statistics from the fact_notification_status table for dates older than today and union that with today.
Tests required.
