Previously we specified the period and calculated the cutoff time
in the function. Passing it in means we can run the method multiple
times and avoid getting "new" notifications to time out in the time
it takes to process each batch.
Previously most of the assertions were being run *before* we had
actually called the function. There was also a redundant block of
assertions that just asserted the initial state of the test data.
We have been running in to the problem in
pallets/flask-sqlalchemy#518 where
our page loads very slow when viewing a single page of notifications
for a service in the admin app. Tracing this back and using SQL
explain analyze I can see that getting the notifications takes about
a second but the second query to count how many notifications there
are (to work out if there is a next page of pagination) can take up
to 100 seconds.
As suggested in that issue, we do the pagination ourselves.
Our pagination doesn't need us to know exactly how many notifications
there are, just whether there are any on the next page and that can
be done without running the slow query to count how many
notifications in total by using `count_pages=False`.
This commit is analagous to
c68d1a2f23
The only difference is that in that case, the pagination links are
used to show prev and/or next links in the admin app. In this case,
the pagination links are only used to see if there is a page 2, and
if there is, say that we are only showing the first 50 results.
In response to [1].
[1]: https://github.com/alphagov/notifications-api/pull/3383#discussion_r759379988
It turns out the code that inspired this new alert - in the old
"timeout-sending-notifications" task - was actually redundant as
we already have a task to "replay" notifications still in "created",
which is much better than just alerting about them.
It's possible the replayed notifications will also fail, but in
both cases we should see some kind of error due to this, so I don't
think we're losing anything by not having an alert.
This will log an error when email or SMS notifications have been
stuck in 'created' for too long - normally they should be 'sending'
in seconds, noting that we have a goal of < 10s wait time for most
notifications being processed our platform.
In the next commits we'll decouple similar functionality from the
existing 'timeout-sending-notifications' task.
Flake8 Bugbear checks for some extra things that aren’t code style
errors, but are likely to introduce bugs or unexpected behaviour. A
good example is having mutable default function arguments, which get
shared between every call to the function and therefore mutating a value
in one place can unexpectedly cause it to change in another.
This commit enables all the extra warnings provided by Flake8 Bugbear,
except for:
- the line length one (because we already lint for that separately)
- B903 Data class should either be immutable or use `__slots__` because
this seems to false-positive on some of our custom exceptions
- B902 Invalid first argument 'cls' used for instance method because
some SQLAlchemy decorators (eg `declared_attr`) make things that
aren’t formally class methods take a class not an instance as their
first argument
It disables:
- _B306: BaseException.message is removed in Python 3_ because I think
our exceptions have a custom structure that means the `.message`
attribute is still present
Matches the work done in other repos:
- https://github.com/alphagov/notifications-admin/pull/3172/files
limit means we only return 50k letters, if there are more than that for
a service we'll skip them and they won't be picked up until the next
day.
If you remove the limit, sqlalchemy prefetches query results so it can
build up ORM results, for example collapsing joined rows into single
objects with chidren. SQLAlchemy streams the data into a buffer, and
normally will still prefetch the entire resultset so it can ensure
integrity of the session, (so that if you modify one result that is
duplicated further down in the results, both rows are updated in the
session for example). However, we don't care about that, but we do care
about preventing the result set taking up too much memory. We can use
`yield_per` to yield from sqlalchemy to the iterator (in this case the
`for letter in letters_awaiting_sending` loop in letters_pdf_tasks.py) -
this means every time we hit 10000 rows, we go back to the database to
get the next 10k. This way, we only ever need 10k rows in memory at a
time.
This has some caveats, mostly around how we handle the data the query
returns. They're a bit hard to parse but I'm pretty sure the notable
limitations are:
* It's dangerous to modify ORM objects returned by yield_per queries
* It's dangerous to join in a yield_per query if you think there will be
more than one row per item (for example, if you join from notification
to service, there'll be multiple result rows containing the same
service, and if these are split over different yield chunks, then we
may experience undefined behaviour.
These two limitations are focused around there being no guarantee of
having one unique row per item.
For more reading:
https://docs.sqlalchemy.org/en/13/orm/query.html?highlight=yield_per#sqlalchemy.orm.query.Query.yield_perhttps://www.mail-archive.com/sqlalchemy@googlegroups.com/msg12443.html
previously we were returning the entire ORM object. Returning columns
has a couple of benefits:
* Means we can join on to services there and then, avoiding second
queries to get the crown status of the service later in the collate
flow.
* Massively reduces the amount of data we return - particularly free
text fields like personalisation that could be potentially quite big.
5 columns rather than 26 columns.
* Minor thing, but will skip some CPU cycles as sqlalchemy will no
longer construct an ORM object and try and keep track of changes. We
know this function doesn't change any of the values to persist them
back, so this is an unnecessary step from sqlalchemy.
Disadvantages are:
* The dao_get_letters_to_be_printed return interface is now much more
tightly coupled to the get_key_and_size_of_letters_to_be_sent_to_print
function that calls it.
we had issues where we had 150k 2nd class notifications, and the collate
task never ran properly, presumably because the volume of data being
returned was too big.
to try and help with this, we can switch to streaming rather than using
`.all` and building up lists of data. This should help, though the
initial query may be a problem still.
We have had a few instances where letters have caused problems. Particularly for precompiled letters, often the issue comes from the same service.
The hope is that by adding a sort order this will help the print provider narrow down the problem.
There is a small degradation of the performance of the query, but it's not enough to concern me.
Our code was assuming that any notifications with `international` set to
`True` were text messages. It was then trying to look up delivery
information for a notification which wasn’t sent to a phone number,
causing an exception.
This done so that we do not use statsd on our http endpoint.
We decided we do not need metrics that this gave us. If we
change our minds, we will add Prometheus-friendly decorators
instead in the future.
Years ago we started to implement a way to schedule a notification. We hit a problem but we never came up with a good solution and the feature never made it back to the top of the priority list.
This PR removes the code for scheduled_for. There will be another PR to drop the scheduled_notifications table and remove the schedule_notifications service permission
Unfortunately, I don't think we can remove the `scheduled_for` attribute from the notification.serialized method because out clients might fail if something is missing. For now I have left it in but defaulted the value to None.
The standard way that we indicate that there are more results than can
be returned is by paginating. So even though we don’t intend to paginate
the search results in the admin app, it can still use the presence or
absence of a ‘next’ link to determine whether or not to show a message
about only showing the first 50 results.
We were doing this temporarily while the `normalised_to` field was not
populated for letters. Once we have a week of data in the
`normalised_to` field we can stop looking in the `to` field. This should
improve performance because:
- it’s one `WHERE` clause not two
- we had to do `ilike` on the `to` field, because we don’t lowercase its
contents – even if the two where clauses are somehow paralleized it’s
is slower than a `like` comparison, which is case-sensitive
Depends on:
- [ ] Tuesday 5 May (7 full days after deploying https://github.com/alphagov/notifications-api/pull/2814)
Like we have search by email address or phone number, finding an
individual letter is a common task. At the moment users are having to
click through pages and pages of letters to find the one they’re looking
for.
We have to search in the `to` and `normalised_to` fields for now because
we’re not populating the `normalised_to` column for letters at the
moment.
It is possible a service has data rention that is smaller than the time it takes to get a delivery receipt.
This PR refactors process_ses_receipt to update NotificationHistory if the Notifcation has already been purged.
Before the search term was either:
- an email address (or partial email address)
- a phone number (or partial phone number)
Now it can also be:
- a reference (or partial reference)
We can take a pretty good guess, by looking at the search term, whether
the thing the user is searching by email address or phone number. This
helps us:
- only show relevant notifications
- normalise the search term to give the best chance of matching what we
store in the `normalised_to` field
However we can’t look at a search term and guess whether it’s a
reference, because a reference could take any format. Therefore if the
user hasn’t told us what kind of thing their search term is, we should
stop trying to guess.
We have a team who want to find emails that might have been sent to an
incorrect address. Therefore they can’t search by the correct address,
because it won’t match.
What they do have is the reference number of the user’s application,
which is also stored in the `client_reference` field on the
notification.
So when a user is searching we should also look at the client reference,
as well as the recipient, allowing the user to enter either in the
search box.
All our endpoint should perform a check that the params are valid - this is an easy whay to check that and is standard for our endpoints.
I reverted the query to just filter by job id.
When we cancel a job, we need to check if all notifications are
already in the database. So far, we were querying for all
notification objects in the database and counting them in
admin app, which runs into pagination problems for large jobs,
and could time out for very large jobs.
Currently we switch if:
* status = delivered and updated_at - sent_at > threshold
* status = sending and now - sent_at > threshold
firetext can leave notifications in the pending state, which is
equivalent to sending in terms of how we should handle it, so this
commit changes the second case to allow pending as well as sending.
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.
